By Mike Koppang

WORRY WHENEVER I GET AN EMAIL from Karilyn at the CAA—I figure I have either once again forgotten to pay my dues, dated a cheque wrong, or done something else to create undue work for association staff in Revelstoke. Thankfully, this time it was simply a request to write about last winter’s busy rescue season out here on the east side of the divide. The 2013-14 season was busy with responses but one event sticks out in my mind, especially in the early season.

The incident occurred in a popular early season ice climbing area known as Ranger Creek, in the Smith Dorrien region of Kananaskis. The climbs in this area see lots of early season ice climbing traffic, in part due to their short, 45-minute approach and short drive from the Calgary/Canmore area. These climbs also, unfortunately, have a long history of catching parties off guard regarding avalanche hazard, and have been the scene of a few burials and accidents. Thankfully, we have had no fatalities in this area related to avalanche accidents, but despite all the public messaging this area still seems to produce an involvement every few years.

PHOTO FROM KANANASKIS COUNTRY PUBLIC SAFETY

The accident occurred in the late morning of November 2, 2013. It was during our first major storm of the season, with relatively small prior snowfalls. The request for assistance came in via a Personal Locator Beacon, which is similar to a SPOT device but transmits its signal to a different call centre coordinated by the Department of National Defence in Trenton. Through the registration details of the device, we were able to determine that it was owned by a European group who were climbing and skiing in the Rockies, and the latitude/longitude of the emergency transmission put it somewhat close to the climbing area up Ranger creek.

Conservation officers who work within the Kananaskis Country Public Safety program responded to the area to look for cars and perhaps talk to people near the trailhead to gather some information and initiate a response. Public Safety Specialists Jeremy Mackenzie and I were unable to fly with Alpine Helicopters from Canmore due to heavy snowfall and limited visibility, and had to respond by ground. Conservation officers on site reported localized weather of S4 with moderate SW winds and 20cm of accumulation on the road since earlier that morning.

As conservation officers reached the trailhead, they observed one person walking out of the area who reported an avalanche above the routes known as Chalice and the Blade and Lone Ranger. These are two 60m grade 4 and 4+ routes located at the head of the valley in complex terrain. The reporting party informed the officer that two separate groups of three people had been walking up to the base of the two routes. As they walked toward the routes, they were discussing the avalanche danger and commenting on changing conditions in the valley due to the associated heavy snowfall. As both parties arrived at the base a few minutes later, they discussed the avalanche danger. As this discussion took place, all six people were struck by an avalanche from the overhead slope. None had any avalanche safety equipment.

Most members of the two separate parties had already put their helmets on during the discussion about the increasing avalanche danger. As a result, their backpacks were off when the avalanche occurred, and what gear they had was scattered across the slope. The slide was 40m wide and ran for 250m. We were unable to get a fracture depth or failure plane, but suspected it to be the October rain crust located just above the ground.

Of the six people hit, two remained on the surface, two were partial burials with their heads above the surface, and two were buried face down. The first person buried face down was able to self-extricate and clear their own airway, but the second was located 100m downslope with only part of a boot sticking out. This person was dug out using hands, helmets and a few ice tools that the two parties still had with them. The victim was unresponsive and the group initiated artificial respirations/CPR and pressed the emergency notification on their personal locator beacon. The victim recovered a few minutes later and amazingly was able to walk out on their own a short while later. No one in the group suffered any major injuries.

I spoke to one of the members of the group back at the trailhead later that morning. They told me that when they first left the parking lot, the terrain around them and the route was mainly gravel or bare rock with some patches of snow. They recognized as they headed up towards the route that the avalanche danger was increasing, but failed to recognize just how quickly it was changing. The contributing factors in the accident were likely this failure to adapt to the new information as it came in combined, with high levels of motivation for that first day out climbing.

Another interesting point is that all people involved were wearing their helmets during the slide, and a few of those helmets suffered damage during the event from striking rocks and other debris. Helmets perhaps minimized the extent of injuries suffered.

During follow-up conversations with two parties, they recognized that were pretty fortunate to sustain only minor bumps and bruises for injuries. They lost lots of gear on the slope, and learned lessons from the near miss. While I did not ask if they would carry avalanche gear on their next outing, I kind of assumed it. One person decided abstinence from ice climbing was an even better approach, which made me chuckle.

Using companion rescue gear while ice climbing is becoming more of a norm these days, as it is advocated by the Association of Canadian Mountain Guides and different guiding companies. If all six people involved had avalanche safety gear at the time of the avalanche, the outcome would not have been that different, as everyone was visible from the surface—luckily. However, having a shovel or shovels would have made the rescue faster and more efficient. Having said that, if the debris had buried the exposed boot just a few centimetres deeper under the surface, there is a good chance that this accident may have resulted in a fatality.

There are lots of good options for lightweight shovels and probes that can be taken ice climbing these days. For me, when the skiing get so bad that I have to go ice climbing, my gear will be with me in my pack.

By Laura Maguire and Jesse Percival

COGNITIVE SYSTEMS ENGINEERING (CSE) demonstrates how expert practitioners in high risk/high consequence domains make sense of risk in dynamic, ambiguous and changing conditions. Expert performance is identified as going beyond qualifications to include the ability to activate, organize and flexibly apply knowledge (Woods et al, 2010) in time pressured, goal conflicted and uncertain conditions. To do so involves cognitive work.

Using methods from CSE, this study assessed the operational aspects of snow safety then analyzed the artifacts (tools such as worksheets, websites, whiteboards, InfoEx, etc.) that shape cognition and collaboration. Semi-structured interviews were used to detail how tools are used to make and update forecasts over time. Finally, we elicited examples of surprise, near misses and actual incidents to calibrate findings.

Three prominent, interconnected themes emerged from the research:

1. Much of the cognitive work is not described in the explicit protocols. The formal representations of what constitutes good practice in forecasting is a small fraction of the strategies experts use.
2. The cognitive effort required to manage avalanche risk is a near continuous activity. Forecasting appears to require ongoing calibration. Disruptions to this calibration process have adverse effects on performance.
3. Forecasting is a distributed cognitive task across individuals, teams and the broader industry. Successful forecasting requires distributed practitioners of local team members as well as the resources and insights produced by others within the industry.

MT. WASHINGTON FORECAST TEAM EXAMINING THE SNOWPACK AND MENTORING NEW MEMBER // JESSE PERCIVAL

PREPARATIONS FOR FORECASTING
Formally, the protocols for a forecaster on duty (FOD) suggests producing a control plan shortly after arriving onsite - but each forecaster interviewed detailed extensive preparations that were not captured by the formal description. A variety of work-related techniques were described. For example, time spent carpooling is used as an informal handoff from one FOD to another to discuss recent activity or control measures. This suggests that formulating the day’s forecast begins well in advance so that a forecaster arrives for duty with a hypothesis of how recent changes in conditions affect their avalanche terrain management.

Shared, off the books activity is a common (and likely necessary) practice not explicitly noted in work procedures and demonstrates a need for ongoing calibration – an example that supports all three findings. It is well documented that forecasting takes place under time pressure. By seeking out data that can help them anticipate conditions in advance, the FOD relieves some of this pressure to lessen the cognitive demands required once they officially clock in.

DISRUPTION, ADAPTATION & SURPRISE
A second example: An unexpected in-bounds release. On this day, the forecasting plan had anticipated instabilities due to temperature changes. After control work, it was expected that normal monitoring would identify if a closure was necessary. However, a personal emergency meant the team was operating one person short. Concurrently, a first aid emergency tied up members who would otherwise be monitoring avalanche terrain. This left the FOD ‘in the bump’ for longer than the usual rotation and his normal practice was interrupted. As expected, the temperature fluctuated and a skier-triggered release occurred in one of the avalanche zones.

This example is informative in two ways. Firstly, it is reflective of what “normal work” is – constantly adjusting to workload demands or unavailability of resources and adapting practices to respond to conditions while balancing inevitable tradeoffs. Secondly, this example provides evidence that practitioners construct mental models (Adams, 2005) and continually update them.

THE BIG PICTURE - MOUNT WASHINGTON // COLE RAMSHAW

MENTAL MODELS
The model is an internal representation of current hazards and an expectation of how this may change over time. Mental models are used to retrieve technical knowledge and to flexibly apply it to variable situations.

In constantly changing conditions, mental models become stale unless continually updated. Referring to the in-bounds avalanche example, the model became insufficient after only a few hours. In the previous example, the forecaster coming back from time off is aware their model is stale and seeks information to recalibrate. LaChapelle (1980) notes a “...prevalent and strong reluctance of working forecasters to experience an interruption in their winter routine…” (pg. 78). This finding emphasizes organizing work schedules to protect forecasters’ daily and seasonal monitoring routine from interruptions or building in mechanisms to support rapid recalibration or redundancy by cross-checking across other team members.

DISTRIBUTED COGNITIVE EFFORTS
Notable as well, is the role of a distributed network in constructing mental models. A diverse range of perspectives informed by different experiences, knowledge and mindsets is needed for accuracy. In the resort, the schedule for FOD’s is designed to provide an overlap day to accommodate the need for distributed cognition. This is an explicit recognition of both ensuring currency of the mental model and the importance of interactions between practitioners. Updating provides an opportunity to draw attention to details and to generate shared insights.

Spatial and temporal constraints also require distributed cognitive efforts. Large terrain and limited daylight hours create time pressures. The FOD relies on technicians to gather and relay data efficiently and accurately. Without the team, the FOD’s mental model can only partially represent actual conditions.

WITH UNCOMMON SNOWPACKS BECOMING INCREASINGLY COMMON, PRACTITIONERS IN A COASTAL SNOWPACK HAVE BEGUN DEPLOYING NEW STRATEGIES // JESSE PERCIVAL

CONCLUSIONS
Errors by normally high performing experts are insights into how the cognitive demands may become temporarily overwhelming. Studies like this illustrate what aspects of practice should be protected from the pressures of ‘faster, better, cheaper’ common in many workplaces and allows for better engineering of the tools, technologies and protocols used.

Further research can provide an empirical basis for: designing decision support tools; developing training; orchestration & distribution of tasks; funding critical resources; and developing new forms of coordination across networks. Identifying cognitive work in different forecasting settings (mechanized skiing, transportation, industrial) is likely to be useful for accident prevention. In addition, CSE studies comparing expert vs recreational cognition is likely to help public safety efforts.

The authors gratefully acknowledge the Avalanche Canada Foundation for their travel support through the ISSW Fund and the Cora Shea Memorial Fund. For the complete proceedings paper or more information about this and other projects in cognitive work of avalanche forecasting contact Laura (maguire.81@osu.edu) or Jesse (jperceival@mountwashington.ca)

REFERENCES:
Adams, L. (2005). A systems approach to human factors and expert decision-making within Canadian Avalanche Phenomena. MALT Thesis. Royal Roads University,
Victoria, BC, 284.

LaChapelle, E. R. (1980). The fundamental processes in conventional avalanche forecasting. Journal Glaciology, 26(94), 75–84.

Woods, D., Dekker, S., Cook, R., Johannesen, L., Sarter, N. (2010). Behind Human Error. London: CRC Press.

By Cam Campbell

Many British Columbians believe that the El Niño-Southern Oscillation index (ENSO) provides a hint of the winter to come. If the index is in a strong El Niño (warm phase), BC’ers gear up for a fat snowpack season. We all remember the winter of 1999: strong El Niño and record snowfall in southwestern BC (Figure 1). This study looks at the validity of using the ENSO and other climatic indices to predict the winter to come. For this study, winter (February 1st) and spring (April 1st) water equivalent of the snowpack (SWE) for seven regions in BC were correlated with four different climatic indices: ENSO, Pacific North American (PNA), Pacific Decadal Oscillation (PDO) and North Pacific (NP).

Motivation for this article came from meteorologist David Jones’ presentation at the 2004 Backcountry Avalanche Workshop on using ENSO as a predictor for West Coast snowfall. In his presentation, David showed that above-average snowfall on the West Coast is sometimes associated with a strong ENSO (warm or cold) but overall the correlation is relatively weak. Several other studies have focused on the relationships between snowpack and hydrologic variability and climatic fluctuations, especially in the Western United States (e.g. Yarnal and Diaz 1986; Cayan and Peterson, 1989; Koch et al., 1991; Redmond and Koch, 1991; Cayan and Webb, 1992; Chagnon et al., 1993; Dracup and Kahya, 1994; McCabe, 1994; Sittel, 1994; Ropelewski and Halpert 1996; Mason and Goddard 2001; Smith and O’Brien 2001; Patten et al., 2003; and the list goes on) but few in Canada (e.g. Moore and McKendry, 1996; Moore and Demuth, 2001).

Figure 1 – Full-depth profile at Fidelity Mtn. in the Columbia Mtns. during the winter of 1999 (Applied Snow and Avalanche Research, University of Calgary (ASARC) photo).

El Niño-Southern Oscillation (ENSO)
The ENSO index is calculated from the standardized pressure difference between Tahiti and Darwin, a small fishing village on the Chilean coast, and represents the effects of an El Niño event on the strength of the equatorial easterlies (Moore and Demuth, 2001). The occurrence of blocking in the Bering Strait is sensitive to the phase of the ENSO cycle and the frequency of blocking is most strongly influenced by the ENSO in January and February (Renwick and Wallace, 1996).

“Blocking” refers to the breakdown of the prevailing mid-latitude westerly flow in the troposphere which produces persistent ridging over the northeast boundary of the Pacific, effectively blocking fronts associated with cyclonic activity over the Aleutian Islands from reaching BC. Sixty-nine percent more days of blocking occurred during the cold phase of the ENSO cycle than during the warm phase, and the frequency of blocking days is 40% lower during the warm phase of the ENSO compared to other winters (Renwick and Wallace, 1996).

North Pacific (NP)
Trenberth and Hurrell’s (1994) NP index represents the intensity of the Aleutian Low in winter and is the anomaly of the areaweighted mean sea level pressure to the mean between 1925 and 1988 for a given area over the North Pacific. Air temperature has been negatively correlated with the North Pacific (NP) index. That is, warm winters are associated with low NP values, whereas precipitation shows a weak positive correlation with NP (Moore and McKendry, 1996).

Pacific Decadal Oscillation (PDO)
As the name suggests, the PDO index is based on oscillations that occur somewhere in the Pacific Ocean every 10 years or so. In fact, it is the time series scores associated with the leading principle component of sea surface temperature in the Pacific Ocean, north of 20°N (Zhang et al., 1997). A positive PDO (warm phase) represents warmer than average water in the equatorial Pacific and colder than average water in the North Pacific, vice-versa for a negative (cold phase) PDO. Moore and Demuth (2001) found that snow accumulation tends to be greater during PDO cold phase winters, which explains lower observed winter accumulation after 1976 when PDO shifted from its cold phase to the present warm phase.

Pacific North American (PNA)
At 55 years old, the PNA index is the youngest used in this study. The PNA index is a mode of winter atmospheric circulation which is naturally and internally generated (Wallace and Gutzler, 1981). Positive values of the PNA (enhanced phase) represent an enhanced Rossby Wave over Western North America with southerly to southwesterly flow over the West Coast which results in warm advection into the southern Coast Mountains (Moore and Demuth, 2001). Moore and McKendry (1996) found that BC winters dominated by enhanced PNA produced overall shallower than average spring snowpack. Intensification of the PNA
index is associated with southwesterly flow over the eastern north Pacific which is likely to cause increased freezing levels and less precipitation, and result in less snow accumulation (Moore and McKendry, 1996).

Methods

Figure 2 – Map of British Columbia showing the eight regions: Northwest, Northeast, Coast, Upper Fraser, Lower Fraser, Thompson, Okanagan-Kettle and Columbia. The snow survey sites used in this study and landmark cities or towns are also marked (Source: British Columbia Ministry of Water, Land and Air Protection)

The BC Ministry of Water, Land and Air Protection (MWLAP) divided the province into eight regions based largely on major drainages. Figure 2 shows the eight regions and the snow survey sites used in this study. The first thing you’ll notice is a lack of sites in the northern half of BC In fact, no sites were used in the Northeast region due to insufficient data so you can disregard the Northeast. The southern regions, on the other hand, have sites with historical data dating back to the mid-1930s. For the sake of statistical significance an emphasis has been placed on the southern half of the province.

Yearly SWE data collected on, or within a few days of, February 1st and April 1st were obtained from the MWLAP’s River Forecast Centre website. The regional average SWE was determined by averaging the SWEs from all snow survey sites used in that particular region. For the case of the Columbia region this means 11 sites (Figure 2), whereas due to insufficient data only one site was used to represent the Lower Fraser and Northwest regions. In order to maintain spatial bias, the average of all regional average SWEs was used to represent the provincial average.

Table 1 lists the websites from which climatic index data were obtained. Most people would agree that the snow usually starts accumulating in the BC mountains sometime in November. For this reason SWE data on February 1st were correlated with the average index values for the previous three months (November, December and January) and SWE data on April 1st were correlated with the average index values for the previous November to March. In doing this, the total amount of snow on the ground is only compared to the index values of the months during which it accumulated.

Table 1 – Websites used to obtain climatic index data

Since all the data were normally distributed, Pearson linear correlation analysis was used to describe the associations between SWE and the climatic indices. Pearson’s R statistic describes the strength of the correlation, with a perfect linear correlation represented by R = 1. The p-value is a function of R and the sample size (N) that quantifies the confidence in the correlation. In this case N corresponds to the number of years in which data were available. Multivariate least-squares linear regression was used to describe the influences that two or more variables may have on a single variable. Multivariate regression analysis produces a Coefficient of Multiple Determination (R2), which is essentially an R statistic for linear associations in more than two dimensions. In order to directly compare the results from the two analysis techniques, Pearson’s R statistic was squared. In accordance with most scientific studies, all correlation and regression coefficients were considered statistically significant at the p < 0.05 level. This means that there is a 5% chance of a Type II error where a coefficient is considered to be statistically significant when in fact it is not.

Results

Provincial
Figure 3 shows time series plots of yearly average PDO, PNA, NP and ENSO indices and provincially averaged SWE for both February 1st and April 1st from 1935 to 2004 (except PNA which doesn’t start until 1950). Consider the three-year period from 1940 to 1942. These winters were characterized by some of the lowest SWE on record and a period of strong La Niña, strong negative NP and strong positive PDO conditions. Now consider the winter of 1999. As
mentioned before, this winter was characterized by high SWE across the province which coincides with strong El Niño, strong negative PDO and relatively weak positive PNA and NP conditions. Interpretation of the remainder of Figure 3 will be left up to the reader.

Figure 3 – Time series of the yearly averages of monthly Pacific Decadal Oscillation (PDO), Pacific North American (PNA), North Pacific (NP) and El Niño-Southern Oscillation (ENSO) index data from 1935 to 2004. Also shown is the provincially averaged Snow Water Equivalent (SWE) for both February 1st and April 1st from 1935 to 2004 (except PNA which doesn’t start until 1950). There is no February 1st SWE data for 1935 and 1936.

At first glance, it would appear that ENSO’s performance is lacking compared to the other indices (Table 2). The correlation with February 1st SWE wasn’t significant and although significant, the correlation with April 1st SWE was weak compared to the other indices. PNA was the best performer, in terms of predictive merit, for both April 1st and February 1st provincial SWE. It is also interesting to note that the correlations with ENSO and NP are positive (i.e. a strong El Niño or NP index corresponds to a high SWE) whereas the correlations with the other indices are negative. Of course, this cannot be seen in Table 2 as all the correlation coefficients have been squared.

Multivariate least-squares linear regression was used to assess the predictive merit of the top three performing indices combined. In this case, PDO, PNA and NP were used according to the following equation: 

When the three indices are combined, the R2 for February 1st SWE was greater than for any individual index, suggesting that more variability can be explained by combining of PDO, PNA and NP. This, however, is not the case for April 1st SWE, where PNA outperforms the combined indices.

Table 2 – Squared Pearson linear correlation coefficients (R2) for the correlations between February 1st and April 1st provincially averaged SWE and each of the four climatic indices. The coefficient of multiple determination (R2) for the equation: SWE = aPDO + bPNA + cNP + d is also given. All coefficients which have a p < 0.05 are marked in bold.

Regional
Once again PDO, PNA and NP in Table 3 seemed to outperform ENSO with more statistically significant correlations and higher overall correlation coefficients. In fact, none of the regions had significant correlations between ENSO and February 1st SWE. All correlations with ENSO and NP are again positive, while all correlations with PDO and PNA are negative. All regions, except the Northwest, had significant correlations between at least one index and February 1st SWE. Once again, PNA seemed to be the best performing index for February 1st SWE, especially for the Thompson, Okanagan-Kettle and Columbia regions. Multivariate least-squares linear regression was again used to assess the combined predictive merit of the PDO, PNA and NP indices based on Equation 1. By combining the three indices, the ability to predict February 1st SWE for all regions, except the Columbia region, was improved. In fact, for the Upper Fraser region the three indices were able to account for 94% of the variability in February 1st SWE.

Table 3 – Squared Pearson linear correlation coefficients (R2) for the correlations between February 1st regionally averaged SWE and each of the four climatic indices. The coefficient of multiple determination (R2) for the equation: SWE = aPDO + bPNA + cNP + d is also given. All coefficients which have a p < 0.05 are marked in bold.

The first thing you’ll notice is an increased number of significant correlations and overall stronger correlations for April 1st SWE (Table 4) than for February 1st SWE (Table 3). Again, PDO, PNA and NP outperformed ENSO in terms of predictive merit. These three indices were, again, combined for regression analysis. By combining these three indices the amount of variability explained by the linear trends was improved for all regions except the Upper and Lower Fraser regions where NP did a better job alone. 

Table 4 – Squared Pearson linear correlation coefficients (R2) for the correlations between April 1st regionally averaged SWE and each of the four climatic indices. The coefficient of multiple determination (R2) for the equation: SWE = aPDO + bPNA + cNP + d is also given. All coefficients which have a p < 0.05 are marked in bold.

Top Five Sites
The top five performing snow survey sites, in no particular order, are: McBride in the Upper Fraser region; Blue River in the Thompson region; Fidelity Mountain in the Columbia region, Sullivan Mine in the Columbia region; and Fernie East in the Columbia region (Tables 5 and 6). ENSO has once again dropped the ball, PDO, PNA and NP, however, look promising (Tables 5 and 6). Again, the correlations with April 1st SWE were stronger than those with February 1st SWE for all sites and all correlations with ENSO and NP are positive, while PDO and PNA consistently show negative relationships with SWE. Once again, a combination of PDO, PNA and NP did a better job of predicting February 1st (Table 5) and April 1st (Table 6) SWE than any of
the indices alone.

Table 5 – Squared Pearson linear correlation coefficients (R2) for the correlations between February 1st SWE for the top five performing snow survey sites and each of the four climatic indices. The coefficient of multiple determination (R2) for the equation: SWE = aPDO + bPNA + cNP + d is also given. All coefficients which have a p < 0.05 are marked in bold.

Table 6 – Squared Pearson linear correlation coefficients (R2) for the correlations between April 1st SWE for the top five performing snow survey sites and each of the four climatic indices. The coefficient of multiple determination (R2) for the equation: SWE = aPDO + bPNA + cNP + d is also given. All coefficients which have a p < 0.05 are marked in bold.

Discussion
The bottom line is: do not rely on ENSO to predict the snowpack depth in the winter to come. The other three indices (PDO, PNA and NP) either alone or combined do a much better job of predicting both February 1st and April 1st SWE at the provincial, regional and individual site scales. Overall, April 1st SWE showed better correlations than February 1st SWE with all four climatic indices. For the most part a combination of PDO, PNA and NP indices will give you the best indication of the winter and spring snowpack to come. For the Upper or Lower Fraser regions in April, your best bet is with NP. Finally, if you like to ski in the Columbia region in February, it’s PNA all the way.

What about the effects of climate change? Well, certainly as our climate continues to change at an accelerated rate, the use of historical climatic data to predict the future becomes less valid. Most climate change models (and there are many) agree that as our climate continues to change, we are going to see more extreme weather patterns. The good news is this means more epic winters like 1999. The bad news is we’ll also see more winters like last year and yes, I realize that it was only extremely bad on the coast. But now that we have these new prediction tools under our proverbial belts we can better decide in the fall whether to buy a new pair of fat boards or spend the money on airfare to South America.

Outlook for next winter? Well, I hesitate to make any predictions because things aren’t looking good and I don’t want to be the bearer of bad news. As of June 2005 the PDO and PNA indices were in a strong positive phase while the NP index was weak, and remember PDO and PNA are negatively correlated with SWE while NP is positively correlated. Anyone interested in a climbing trip to Chile?

Acknowledgements
I would like to thank Dr. Bruce Jamieson for proofreading this article and for providing statistical expertise. I would also like to acknowledge Dr. Dan Moore for providing the idea and proofreading the original draft of this article.

References
Cayan, D.R., and D. H. Peterson. 1989. The influence of North Pacific atmospheric circulation on streamflow in the west. Aspects of Climate Variability in the Pacific and Western Americas, Geophys. Monogr. Ser., 55, 375- 397.

Cayan, D.R., and R. H. Webb. 1992. El Niño/Southern Oscillation and streamflow in the western United States . El Niño: Historical and Paleoclimatic Aspects of the Southern Oscillation. Cambridge University Press, New York, USA. pp.29-68.

Chagnon, D., T. B. McKee and N. J. Doesken. 1993. Annual snowpack patterns across the Rockies: Long-term trends and associated 500-mb synoptic patterns. Mon. Wea. Rev., 121, 633-647.

Dracup, J.A. and E. Kahya. 1994. The relationships between U.S. streamflow and La Niña events. Wat. Resour. Res, 30, 2133-2141.

Koch, R.W., C. F. Buzzard and D. M. Johnson. 1991. Variation of snow water equivalent and streamflow in relation to El Niño/Southern Oscillation. Proceedings of the1991 Western Snow Conference, April 12-15, Juneau, U.S.A. pp. 37-48.

Mason, S. J. and L. Goddard. 2001. Probabilistic precipitation anomalies associated with ENSO. Bull. Amer. Meteor. Soc., 82, 619–638.

McCabe, D. J. Jr. 1994. Relationships between atmospheric circulation and snowpack in the Gunnison River basin, Colorado. J. Hydrol., 157, 157-175.

Moore, R. D. and M. N. Demuth. 2001. Mass balance and streamflow variability at Place Glacier, Canada, in relation to recent climate fluctuations. Hydrol. Processes, 15: 0-0 (2001).

Moore, R. D. and I. G. McKendry. 1996. Spring snowpack anomaly patterns and winter climatic variability, British Columbia, Canada. Wat. Resour. Res, 32, 623-632.

Patten, J. M., S. R. Smith and J. J. O’Brien. 2003. Impacts of ENSO on snowfall frequencies in the United States. Bull. Amer. Meteor.Soc., 18, 965–980.

Redmond, K. T. and R. W. Koch. 1991. Surface climate and streamfl ow variability in the western United States and their relationship to large-scale circulation indices. Wat. Resour. Res, 27, 2381-2399.

Ropelewski, C. F. and M. S. Halpert. 1996. Quantifying Southern Oscillation–precipitation relationships. J. Climate, 9, 1043– 1059.

Renwick, J. A. and J. M. Wallace. 1996. Relationships between North Pacifi c wintertime blocking, El Niño, and the PNA pattern. Mon. Wea. Rev., 124, 2071-2076.

Sittel, M. 1994. Differences in the means of ENSO extremes for maximum temperature and precipitation in the United States. Center for Ocean–Atmospheric Prediction Studies Tech. Rep. 94-2, Florida State University, 50 pp.

Smith, S. R. and J. J. O’Brien. 2001. Regional snowfall distributions associated with ENSO: Implications for seasonal forecasting. Bull. Amer. Meteor. Soc., 82, 1179–1191.

Trenberth, K. E. and J. W. Hurrell. 1994. Decadal atmosphere-ocean variations in the Pacifi c. Clim. Dynam., 9,303-319.

Yarnal, B. and H. Diaz. 1986. Relationships between extremes of the Southern Oscillation and the winter climate of the Anglo–American Pacific coast. J. Climatol., 6, 197–219.

Zhang, Y., J. M. Wallace and D. S. Battisti. 1997. ENSO-like interdecadal variability: 1900-93. J. Climate, 10, 1004-1020.

By Thomas Exner¹ and Bruce Jamieson²
ASARC – Applied Snow and Avalanche Research, University of Calgary
^{1 Dept. of Geoscience, University of Calgary
2 Dept. of Civil Engineering, University of Calgary}

<sup>Many people associate snow pack warming with spring-like conditions, when snow temperatures are close to 0°C and the likelihood of wet avalanches increases rapidly as soon as the sun softens up the melt-freeze-crust that often forms during cool nights. This is a common scenario in spring, when signs of warming, such as relatively warm air temperatures, strong solar radiation, and moist surface snow are easy to observe. But, what happens to a cold, dry snow pack that warms up significantly at air temperatures below zero?

In this article we discuss a few concepts of stability changes caused by daytime warming and summarise results from reported avalanches mainly caused by solar warming of a dry snowpack. These cases are quite rare, but under the right conditions warming can be the significant factor decreasing stability. According to a Swiss study (Harvey and Signorell, 2002) in 20% of 128 avalanche accidents in the Swiss Alps, daytime warming was the only factor contributing to avalanching. On those days no significant amount of new snow or recent wind loading was reported. Of course, maybe in some of those cases there may have been just a lingering instability, which could have been triggered by a skier regardless of the warming. However, the 20% suggest a significant correlation to the influence of warming.</sup>

^{Figure 1: Figure 1. This dry slab avalanche was triggered on a cold, sunny day by a skier on a steep south-west facing aspect. Solar warming may have contributed to this release. (photo: ASARC)}

<sup>What are the sources of warming that can rapidly increase the temperature of near surface layers?
The main warming sources that effectively are able to increase avalanche danger are solar warming, rain, and warm, strong winds. Rain is probably the most efficient way of adding heat to the snowpack (Marshall and others, 1999). It destabilizes the snow pack in a short time, can penetrate down to deep layers, and affects all aspects. Luckily, mid-winter rain events are rare in alpine regions in most places in Western Canada. Warm, dry winds, such as the Chinook are known to cause rapid warming of the near surface layers and may reduce snow pack stability. But, these warm wind events are infrequent, except on the eastern slopes of the Canadian Rockies.

The most frequent cause of near surface warming seems to be direct solar radiation. It can warm up the upper layers of the snow pack rapidly within hours and affect the stability of the snowpack down to about 30 to 50 cm (McClung and Schaerer, 2006, p.38). By softening the surface layers, loads (e.g. skiers or snow boarders) may even affect deeper layers. Thin clouds may intensify the heating effect by trapping radiation between the snow pack and the clouds (greenhouse effect). 

The effect of time
Usually, warming of a dry snowpack is associated with increased settlement of the snow pack, and non-persistent (storm snow) weak layers are believed to be stabilizing under these conditions. This seems to be the case as long as the settlement happens slowly and gradually (McClung and Schweizer, 1996). Settlement and creep are always connected with a deformation of the snowpack, and snow as a material can adjust to slow changes in deformation without damage. However, fast deformation, as sometimes observed during rapid warming events, can result in collapse of the snow micro-structure (bonds are breaking faster than new bonds are forming), and a layered snowpack may release slab avalanches.

So, slow warming and settlement of the snowpack usually promotes stability. But, of course, there is an exception to this rule. Imagine for example a surface hoar layer, buried under a layer of low density snow with low cohesion (Fig. 2). No matter how hard a skier, boarder or snowmobiler hits this layer there is no slab to release. But with ongoing settlement, even when slow and gradual, the overlying layer(s) will increase in stiffness and density (become “slabby”). Now it may not take a lot to trigger and propagate a fracture in the surface hoar layer, and release a slab avalanche. This process requires a pre-existing persistent weak layer, such as the surface hoar layer.

In most cases when rapid solar warming, within a few hours or so, increases avalanche danger the slab/weak layer combination is mostly already like a “loaded gun.” The warming speeds up the creep of the slab on the weak layer just enough to possibly trigger a natural slab avalanche. Keep in mind we are still talking about a dry, sub-freezing snowpack. Once the snow surface starts to melt we are dealing with moist or wet point releases, which are a different story not addressed in this article. However, there are few cases where rapid solar warming significantly decreased stability, even though an obvious weak layer was not observed. The following section summarizes the conditions when this phenomenon was observed.</sup>

<sup>Figure 2. Even a prominent surface hoar layer with loose, low density snow on top is not releasable (left); neither by a skier nor as a natural avalanche. After the surface layer settles into a slab a fracture can propagate along the weak layer and release a slab avalanche (right). Daytime warming accelerates the settlement process and may act as a trigger.

Low density snow and rapid solar warming
According to the results of a survey conducted amongst 35 experienced avalanche practitioners in the fall of 2006, numerous reports of solar warming related avalanches followed a similar pattern. In all of these cases obvious signs of instability (shooting cracks, whumpfing and skier-triggered avalanches) developed during a short period of strong solar warming after the snow pack initially appeared to be stable and, interestingly, no obvious weak layer was observed initially. A few of these cases were reported by mechanised skiing operations, where a run was skied several times during the warming period. Snowpack observations ranged from no signs of instability on the first run to shooting cracks and triggered slabs within hours on the following runs. The following list summarises conditions, each of which were reported in a number of incidents.</sup>

• East to south-east facing slopes (35-40°)

• Air temperatures well below zero (in the -8° to -15°C range)
• Clear skies, strong solar radiation in the morning hours in March or April
• First sunny day after a storm
• Cold, low density near surface layer
• No signs of warming (snow surface still dry)
• Initially stable snowpack, no obvious weak layers

We assume that rapid solar warming and settlement stiffened up the near-surface layer and so turned into a releasable slab (Fig. 3). A buried, subtle storm snow layer may have turned into a reactive sliding surface with the stiffening slab on top. With ongoing warming this temporary stage of instability probably stabilizes subsequently due to strengthening of the storm snow layer. Potentially, the interface of the warmer and denser layer overlying the still colder and less dense layer may have acted as the weak layer. Attempts to model this interface with a numerical snowpack model have been inconclusive so far. The idea of a storm snow layer becoming the reactive weak layer seems to be more likely.

Figure 3. A cold low density layer can settle in to a reactive slab within hours caused by strong solar radiation. A subtle storm snow layer or just the interface of the stiffer, warmer layer above the low density snow may become the weak layer.

We set out to track down these warming events and gather more detailed data over a limited number of days during the winter of 2006/07. So far, we have not been able to observe this phenomenon. Even when conditions seemed right, we only observed the settlement and stiffening of the surface layer but could not fi nd any signs of decreasing stability. So, what happened? It seems like this scenario is a complex interaction of many factors, such as warming rate, temperature range, snowpack properties, presence of an initially subtle weak layer, slope angle, aspect, and so on, which is so far poorly understood. In some of our observations some clouds may have delayed the warming or snow temperatures were too high, softening the slab and preventing propagation.

Nevertheless, the reported cases seem to suggest that solar radiation can temporarily promote slab avalanching without a pre-existing obvious weak layer. The case where an obvious persistent weak layer (e.g. surface hoar, rain crust), with a stiffening layer on top, turns into a reactive slab is a more common scenario and easier to recognise, even though experienced people have been surprised by it. Once the slab on such a layer has formed, unstable conditions can prevail for quite a while. In most of the cases reported here, the temporary stage of increased avalanche danger may just last for a few hours or so. The storm snow layers, or perhaps the interface gains strength quite rapidly with ongoing settlement and warming.

Other recent observations 

In this winter season of 2007/08, a number of natural slab avalanches released in January above ice climbs in the Rockies on steep sunny aspects. Most of these avalanches released in the first few days after a storm on a sunny day and air temperatures were well below zero. Usually, at this time of year it is quite uncommon that solar radiation releases slab avalanches. Perhaps the combination of the weak snowpack in the Rockies this winter and still sufficiently strong solar radiation on steep sunny aspects was a factor in releasing these avalanches. Given the weak, unstable snow pack even the low January sun provided enough warming to act as a trigger. In the spring time it is more common for avalanches above ice climbs to start as moist point releases and may eventually step down to a weak layer and release a slab avalanche.

Snowpack warming model – SWARM

Most of the above reported scenarios showed air temperatures well below the freezing point, and obvious clues such as a moist snow surface and snow balling were missing. Without many years of experience these warming conditions are hard to recognise and can easily be overlooked, but still can lead to a significant increase in avalanche danger. From field observations we know that only a few degrees difference in slope angle or aspect have a strong effect on the amount of heat the snow surface layers absorb. This winter for instance, we observed a sun crust on steep south-facing terrain above 40° or so on a cold day in January with air temperatures in the -15 to -20°C range. On parts of the slope with only a minor change in angle or aspect the snow surface was still dry.

Laura Bakermans, a former grad student with ASARC, developed a snow pack warming model (SWARM) based on extensive temperature measurements of near surface layers to evaluate the influence of solar radiation depending on slope angle, aspect and time of year (Bakermans, 2006). Of course, it is not only the amount of daytime warming possibly raising avalanche danger on warming days. There are many other contributing factors. However, solar daytime warming is often underestimated on cold days when signs of warming are not obvious. Experienced people may know through intuition, based on many years of experience, when warming effects come into play. SWARM may help to train your intuition and shorten this learning process. Hogarth (2001), in his book “Educating Intuition”, would describe avalanche terrain as a “wicked” learning environment, since feedback is not always immediate or obvious, and it can have high consequences. On days when warming may be an issue it is probably wise to leave a wider margin of safety. There is still a lot to learn about the interaction of daytime warming and slab avalanching. SWARM is freely available for download on the ASARC web page (http://www.schulich.ucalgary.ca/cgi-bin/ENG/TrackIt.pl?SWarm.xls). Feel free to contact us if you have any questions, suggestions or comments.

Acknowledgements

Many thanks to all guides and forecasters, who kindly shared their knowledge and experiences on warming-related avalanches.

References

Bakermans, L., B. Jamieson. 2006. Measuring near-surface snow temperatures changes over terrain. Proceedings of the International Snow Science Workshop in Telluride, Colorado, 377-386.

Harvey S., C. Signorell. 2002. Avalanche accidents in back country terrain of the Swiss alps: New investigations of a 30 year database. Proceedings of the International Snow and Science Workshop, Penticton, B.C. The Canadian Avalanche Association.

Hogarth, R.M. 2001. Educating intuition. The University of Chicago Press, Chicago, U.S.A., 357 pp.

Marshall H.P., H. Conway, L.A. Rasmussen. 1999. Snow densification during rain. Cold Regions Science and Technology, Volume 30, Issues 1-3, 35-46.

McClung, D.M. , J. Schweizer. 1996. Effect of snow temperatures on skier triggering of dry slab avalanches. Proceedings of the International Snow Science Workshop in Banff, Alberta. Canadian Avalanche Association, Revelstoke, BC, 113-117.

McClung, D.M., P.A. Schaerer. 2006. The Avalanche Handbook. The Mountaineers, Seattle, Washington, U.S.A., 342 pp.

By Julie McBride

FOR MARMOT BASIN, Friday, January 29, 2016 marked the end of a nearly two-month drought. Although November blessed us with a dump of snow during our opening week, December and January had forsaken us. Our last appreciable snowfall had been seven weeks prior on December 9. The arrival of the much anticipated storm was also the harbinger of a human-triggered avalanche cycle from the Icefields Parkway to McBride, BC. A total of five separate events involving avalanche professionals as well as recreationists all occurred within a 200km radius of Marmot Basin. It was a busy day in the avalanche world near Jasper, one that would ultimately cast a sombre shadow over our operation for the remainder of the season.

During the drought, temperatures had ranged from just below –20°C to just above freezing with a week of sustained cold. With less than 90cm of snow on the ground, Marmot’s was a textbook continental snowpack—shallow and weak, facets throughout, sitting on a base of depth hoar. Although the “storm” delivered only 8cm of snowfall in 24 hours, it was accompanied by moderate to extreme southerly winds, that formed a new storm slab. Friday, January 29 was our first avalanche control morning in weeks.

PHOTO: AERIAL SHOT OF MARMOT BASIN // MARMOT BASIN

As the forecaster that morning, my first priority was an Avalauncher shoot that produced results from size 1 to 2.5, with the larger releases initiating in the storm slab and then stepping down to a layer of facets and depth hoar, 50-70cm down. Satisfied with these results, I turned my attention to Charlie’s Bowl.

A northeast to southeast-facing alpine bowl with a series of steep, rocky chutes below its entrance adjacent to the Knob area, Charlie’s Bowl had not yet opened for the season. In mid-November, Chutes 5 through 7 had released to ground during a natural cycle. A week later, Chutes 5 and 6 failed to ground with explosive control work. With more explosives in December, Chutes 6 to 9 released to ground for a third time. By mid-January, ski cuts produced only small results in isolated pockets of thin wind slab. We began ski compacting and waited for more snow to open Charlie’s to public. Late in the afternoon on Thursday, January 28, with over 100 sets of tracks around me, I stood at the top of the Chutes, snow and wind obliterating my visibility, hopeful that we might be getting close.

The first two one-kilogram hand charges in Charlie’s Bowl on the morning of the 29th produced no results. Two more 1kg charges, deployed simultaneously at either end of a broad apron above the Chutes, also failed to produce a result. With no more explosives, I proceeded to ski cut from my position at the top of Chute 8. Once I was clear, my partner, one of our avalanche technicians, did the same in Chute 5. While ski cutting we both noted a 10-15cm thick, 1F slab that was penetrable on skis, but no signs of fracture propagation or releases other than small fist-sized slab cookies. Then I decided: the avalanche tech would take two patrollers and continue ski cutting in Charlie’s to break up the slab, while I moved on to another area with a third patroller.

PHOTO: CHARGES LARGE AND NUMEROUS // MARMOT BASIN PATROL

Minutes after we’d parted ways, I got a call over the radio from one of the two patrollers in the Chutes: “We’ve had a deployment; he’s on top…” Oh shit. The tech had gone for a ride. Then a second call from the tech: “I’m ok.” Thank God.

As the tech skied into Chute 6, a small pocket of wind slab had propagated into the rocks above him and then stepped down to ground. With no escape, he’d deployed his air bag and was swept by a size 2 for nearly 200m to the flats at the base of the chutes. Spotting from above, his partners reported that he’d been on top of the slide the entire time and that when it came to a stop, he appeared to be sitting upright in the debris, his legs buried to the hip. He had lost both skis and one pole but was able to selfextricate. By the time his partners had made their way to him, he was free and clear of the runout zone, a bit shaken but understandably so. Although he had tweaked his lower back while twisting to release from his skis, he had somehow managed to otherwise emerge physically unscathed from a rather nasty ride through some very thin, bony terrain.

No stranger to ski cutting, it was the tech’s third involvement during his seven-year tenure at Marmot. His propensity for triggering avalanches was already well established. At 6’8” and 260lbs, he has been known to trigger slopes where even large explosives have failed. His skis sink deep into the snowpack and he has a knack for finding the sweet spot. 

In addition to his formidable stature and reputation, his pursuits outside of work invoke similar images of unbreakable nerve and strength: base jumping, parachuting and backcountry sledding. This is someone who had been hired as an avalanche tech not only for his knowledge and experience, but also for his ability to remain stolid and clear-headed in stressful situations. It came as no surprise that after debriefing with the control team he was ready to get back on the horse, so to speak.

Back at the top of Chute 6, he gladly volunteered to place a 6.75kg sack of explosives into the hangfire. The shot cleaned out what was left, taking Chute 7 to ground along with it and releasing the thin storm slab in Chutes 8 and 9, which ran over top of the ski cuts in Chute 8 from a few hours earlier.

PHOTO: A SA IN CHUTE 6 AT MARMOT BASIN // JASON RECHNER

That afternoon, details of other larger events to the south and to the west of Marmot began to circulate on the news and within industry channels. A Visitor Safety Officer from Jasper National Park had been involved in a skier-accidental size 3 that deposited nearly two metres of debris on the Icefields Parkway near Parker Ridge, closing the highway. And at least 15 snowmobilers from three separate groups were involved in a size 3 machine accidental near McBride that resulted in the deaths of five snowmobilers.

Amidst these rumours and half reports I went home that night and contemplated the decisions I had made that day: where I had failed, what I could have done differently, what I had learned, what I would do differently now, what I would do in the future. My head reeled from the cerebral merry-go-round.

As avalanche professionals we spend a great deal of time talking about avalanche problems and avalanche hazard, and how things like variability, uncertainty and confidence play into our analysis of what the problem or hazard actually is. We also talk about human factors: nebulous sub-conscious phenomena that can sometimes lead us to miss or misinterpret pieces of information, or bias our intuition and instincts. Even though we employ various tools, decision aids, methods and procedures to avoid mistakes of both the analytical and the human kind, sometimes unexpected or unlikely things happen. Sometimes we get caught in slides. That is just the nature of snow on steep slopes. And it is why we also practice and teach avalanche rescue skills. There is always uncertainty and sometimes we get it wrong.

While I knew that my decision to continue ski cutting that morning had turned out to be a bad one, the reality is that the possibility of going for a ride exists every time I or someone else ski cuts a slope. Still I couldn’t help feeling that I’d let the team down, in particular the tech who had been the victim of my decision. An element of complacency had crept in during the drought. Having seen little change from day to day for seven weeks, I’d underestimated the effect of a little bit of new snow and some wind on our deep persistent layers and what a light trigger in the right spot could do, even in worked terrain. My confidence was rattled. Our snowpack was weak and unpredictable, and the head forecaster and I resolved to punctuate future
control missions with larger explosives.

PHOTO: JULIE AND THE TECH INVOLVED // JASON RECHNER

In the week that followed, it was obvious that the tech who’d been involved was clearly struggling to deal with how he had been affected. He was having trouble sleeping, he was having nightmares, his hands trembled, his head just wasn’t in the game and the pain in his lower back had worsened. We sent him to a doctor, a physiotherapist and a critical incident stress counsellor. We filed a workers’ compensation claim and he was placed on light duties.

The physiotherapy sessions continued, the counselling sessions continued. Weeks passed, then months. His mood and progress seemed to ebb and flow. Every day was a different day, each with possibly a different challenge. He started experiencing panic attacks. He was frustrated. With no manual, tools or methods guiding us in supporting him, we—his supervisors—were frustrated. We talked, we talked with him, we talked with our managers, we talked with WCB, then we talked some more. I suggested that perhaps some time completely away from the work environment would help. He opposed; he felt that his anxiety was something he had to face head on and that stress leave would be counterproductive to learning how to overcome it. I was skeptical but conceded. After all, I was no expert and I admired his dogged determination. He was doing everything right. And while he struggled, the rest of us carried on, not for lack of compassion but for lack of other options.

The season continued much as it had begun, with little snowfall and low confidence in our snowpack. We opened most of our avalanche terrain eventually. Large and numerous explosives continued to produce large avalanches running on deep persistent weaknesses. We were cautious and conservative. Temperatures remained above freezing throughout most of April. An impressive iso-cycle ripped out moguled runs down to the basal depth hoar; our suspicions were vindicated. As we packed up our gear on our final day of the season, the tech was clearly still struggling. I watched the panic wash over his face when someone deployed an avalanche airbag for summer storage, triggering a flashback and the anguish of his trauma. My heart broke. It’s the last day, what happens now?

The tech has since been diagnosed with an adjustment disorder. Over the summer worked with a team of professionals (a psychologist, occupational therapist and a physio/personal trainer) overseen by a specialist in traumatic psychological injuries. It is still a long road ahead but one that he is facing with courage and optimism. He is Hercules to me, and like all parables his trials hold a lesson for us.

When avalanche professionals talk about human factors, we need to talk not only about what goes on in the subconscious prior to our decision of whether or not to ski into a slope, but also potential consequences of that decision at the psychological level as well. Although we find it easy to casually discuss the physical consequences of an avalanche with euphemisms such as “raked through the trees” or “cheese-grated over the rocks,” we rarely discuss how the same event might affect one’s mental health. Or if we do, it is often in hushed voices, behind closed doors: “Why can’t she just deal with it?”

That is because psychological or mental health issues of any kind have a stigma in society in general. It’s not polite to talk about the elephant in the room or the crazy uncle in the attic, so to speak. And this is precisely the reason why we need to talk about it, because the patroller who goes to a wreck or the tech who goes for a ride or the guide whose guest gets buried might not be able to. They might not even recognize that they’ve suffered a traumatic psychological injury, never mind have the strength to admit it to themselves and ask for help. As their supervisors, we need to build our knowledge and understanding of “mental health first-aid” and have these tools in our proverbial tool-boxes when we start the conversation.

By Rod Gee

My 25 year glide slab education began on an early morning in January 1989. A snowplow operator on Highway 16 west of Terrace reported witnessing a Size 3.5 airborne wet avalanche cross the railroad and highway corridors.

The deposit pushed sections of concrete guardrail into the Skeena River. Fortunately, no one was involved. I arrived at the site shortly after hearing the plow operator’s report. “Argh! It’s the glide slab I’ve been monitoring for the last week," I thought; "Why this morning? It’s notraining, and it’s not warm. Why did it run now? Were there indicators I’d missed?”

I came to the north coast of British Columbia to work in CN Rail’s Skeena avalanche program. I brought seven years of work experience in the Rockies, and ITP training in the Selkirk Mountains and the Coast Ranges. However, I had minimal knowledge of glide slab behaviour.

Glide slab prediction is a challenge, compared to the relative predictability of most maritime snowpack avalanche activity. They are classic poster children for the discussion surrounding why “Hazard Level 2” is perhaps a better descriptor than “Stability Good, with the occasional size 4.” Without start zone instrumentation monitoring glide rates, the CN Skeena program offsets uncertainty to some degree with frequent explosives control, and, where effective, runout zone earthworks.

Glide slab explosives control results, 50 mile path. Skeena River corridor, west of Terrace, BC // Rod Gee

These are some of the observations on formation and natural initiation I now use to evaluate glide slab stability:

• A low-friction ground surface is important for slab formation, but the degree of support from terrain features immediately below the slab is at least as important for slab failure.
• Rapid, early season snowpack accumulation associated with relatively warm air temperatures increases the likelihood of early- and mid-season glide slab formation.
• Lack of an effective ground freeze prior to snowpack accumulation results in increased mid-winter glide rates.
• Rainfall and meltwater percolation in an isothermal starting zone snowpack may accelerate glide rate by decreasing friction at the slab/ground interface. Free water may also decrease the strength of the supporting snow downslope of the glide slab as well as the slab itself. Rain falling into the glide crack above the slab, likely has a similar net effect. However, rain does not guarantee slab failure; it is only part of the equation.
• Glide slab failure does not require an isothermal snowpack. Failure may occur before the snowpack becomes isothermal or during the overnight cooling phase of the diurnal cycle, and without free water being present at the snow/ground interface.

Explosives Initiation
The ideal condition for explosives control occurs when the slab itself maintains a degree of strength greater than that of the snowpack below the toe and along the flanks of the slab. In an ideal scenario, a combination of terrain and weather factors unbalances the downslope snowpack stress/strength relationship to a greater degree than within the slab itself. The toe and flanks are now barely able to support the loading of the gliding slab. Explosives applied at this time cause slab initiation by triggering a failure of the snowpack at the toe of the slab.

Technicians Herb Bleuer and Mike Zylicz began experimenting with charge quantity and placement in the Skeena corridor in the early 1980s. They realized that conventional charge quantity was usually insufficient for glide slab initiation, and that charge placement was extremely critical. They also realized that placing the explosives charge into the glide crack above the slab was ineffective because that was not where the stress/strength relationship was deteriorating. Effective glide slab control is about “kicking the knees out” from under the slab, and not adding load to the slab itself. Their testing produced reasonable results using 100-150kg ANFO charges placed at the toe of the slab.

The best charge placement is a very specific point where the gliding slab is having the greatest effect on the non-gliding downslope snowpack. Current Skeena corridor glide slab control strategy includes the use of charges of 150 and 500kg on 200-500cm deep slabs. Large charges are used
because they increase the likelihood of triggering, which reduces hazard at the runout zone transportation corridor and minimizes the likelihood of natural events disrupting rail operations.

That said, control is not always successful. A complex, ever-changing interplay of factors affects glide slab stability, and the puzzle is not completely understood. Some factors I consider in evaluating explosives control effectiveness include:

• Control is more likely to be successful on glide slabs poorly supported by the terrain below the slab. For example, a poorly-supported glide slab can be initiated with explosives so it will then trigger a better supported glide slab lower in the starting zone that does not respond to explosives.
• Rain or melt-water at the ground/snow interface is not essential for initiation to occur, but it does increase the likelihood.
• Initiating sections of glide slabs is useful both by reducing the deposit volume of a single occurrence, but also because it exposes the ground surface to solar radiation, which then potentially aids in increasing glide rate by introducing more heat into the slab’s basal layers. 
• The strength of the snowpack below and alongside the slab allows the slab to glide a significant distance downslope without failing. Increasing glide rate may indicate decreasing snowpack strength.
• A 300-600cm slab can easily glide 50-100m without initiating if the downslope snowpack and terrain accommodates the glide’s loading effect. Increasing glide rate and/or deteriorating strength of the snowpack supporting the slab are two critical initiation factors.
• Three reliable nearby indicator paths I use to assess an east aspect path prone to glide slab formation have a northwest aspect, but the starting zones are at the same elevation. This suggests ambient air temperature affects glide slab behaviour to a lesser, but still relevant, degree.

Prediction and control have improved since the 1980s, but we still include a healthy dose of “art” to the “science” of our craft. Explosives control in January 2012 put a size 4 deposit within 2m of the rail roadbed. Is our understanding of glide slab management improving, or were we just lucky on that mission?

AVALANCHE CANADA FORECASTER GRANT HELGESON TESTS SOME PROTOTYPE FORECASTING TOOLS. // ALEX COOPER

WEATHER FORECASTING HAS RADICALLY transformed over the past century. In the 1920s, field observers reported current weather conditions back to meteorologists, who would draw up weather maps and extrapolate the weather for the next few days. Fast forward 100 years and precise forecasts are possible in mountainous terrain thanks to a global network of earth observations, advances in scientific understanding, and some of the most powerful supercomputers in the world. 

This raises the question, will avalanche forecasting head down a similar transition from field-based to computer-based work?

Certainly not anytime soon, but some form of technological progression is inevitable. The transition for weather forecasting took decades, starting around the time of the Second World War. Growth in aviation enhanced our interest in the atmosphere, that in turn changed our perspective of the weather. In the decades that followed, space exploration led to weather satellites that gave us an even broader view of the atmosphere. Then, early computers began crunching numbers to help with these extrapolations.

Despite these technologies, weather forecasting remained deeply rooted in experience-based pattern recognition for several more decades. By the 1970s, computer models began giving reasonable upper air forecasts (such as jet stream forecasts), but the Second World War-era style of human-centric forecasting still prevailed. the tides turned in the 1980s and 1990s when computer forecasts became more accurate and forecasters eventually learned when they
could and could not trust them. Trust in the ability of computer models to accurately predict weather continues to grow.

Avalanche forecasting currently relies on manual field observations and experience-based pattern recognition comparable to methods used by Second World War-era weather forecasters. However, over the past decades, the avalanche research community has developed remote sensing and computer modelling methods that have similar potential to observe, understand, and predict avalanche conditions. These technologies are at a similar status to weather forecasting technologies from the 1960s or 1970s. New methods are becoming available, but we don’t really know how to implement them into daily work.

As we saw in weather forecasting, these barriers were eventually overcome as the technology improved. We can speculate what a future avalanche forecasting system might look like by looking at how similar technology transformed weather prediction.

OBSERVATIONS AND PREDICTIONS
Modern weather forecasters use interactive dashboards that combine field observations, satellite imagery, and computer predictions to form a comprehensive picture of current and future weather conditions. Could this be what our workspaces look like in the future? Maybe instead of simply reviewing field observations from your own and neighbouring operations, a future avalanche forecasting tool will combine these observations with automated maps of avalanche activity, virtual snow profiles, and computer predictions of future conditions. to help form a more comprehensive picture of avalanche hazard. Even if it’s speculation, it’s important to understand the potential for technology to change avalanche work so we can shape it in a way that we all benefit.

The technologies impacting weather and avalanche forecasting broadly fit into two categories: ones that observe the conditions and ones that predict the conditions. In terms of observing conditions, weather satellites were the game changer that allowed us to expand from point observations to continuous spatial coverage. The same thing could happen with avalanche and snowpack observations. Networks of detectors that sense vibrations from avalanches are already installed, and recent research out of Europe has shown impressive accuracy in detecting avalanche debris in near real-time using radar-based satellites. Testing in Norway has found these satellites, which can even see through clouds, can provide updated daily maps of avalanche debris with complete spatial coverage across mountainous terrain. Imagine being able to see map of every avalanche that ran in Canada over the past 24 hours!

Remote sensors—from either satellites, aircrafts, drones, or on the ground—can also tell us about the snowpack. Deriving maps of snow-covered areas is already straightforward, but there is an increasing ability to sense snowpack layering remotely too. There are still many hurdles to getting actual x-ray vision into the snowpack—detecting thin weak layers is difficult, wet snow and crusts create a lot of errors, and all remote sensing technologies struggle in steep complex terrain. Advances in remote sensing are happening quickly, but most likely will need to be supplemented with other information to give us the best possible picture of avalanche conditions.

This is where prediction comes in. Our understanding of weather evolved in the 1920s with improved theories about the 3D structure of frontal systems. This didn’t have much impact on forecasting until several decades later when these theories were applied in computer models. This has become the backbone of modern weather forecasting.

Similar advances in snow science over the past decades have enhanced our understanding of how weak layers form, how avalanches release, and how they move downslope. The latest theories about snow microstructure and fracture mechanics are being implemented into computer models that simulate both the evolution of the snowpack structure as well as the movement of avalanches once they release. Could these models eventually have as much predictive power as weather models?

VIRTUAL SNOW PROFILES

A VIRTUAL SNOW PROFILE CONTRASTED WITH A HAND DRAWN ONE // SIMON HORTON

 One promising forecasting application is computer models that simulate snow profiles with weather and terrain data. Some European countries started testing virtual snow profiles in the 1990s and Avalanche Canada started testing similar products 10 years ago with a focus on remote, data-sparse areas where the models could be driven with weather forecasts. (You may have seen these virtual profiles on ARFI.) Since their inception, the consistent question is, "How accurate are they?" 

After 10 years of developing and testing these models for public forecasting in Canada, our impression is they provide a reasonable picture of general snowpack patterns, at least at some of the locations some of the time. Similar to how early weather models provided semi-realistic jet stream forecasts, the latest snowpack models can provide some big picture context to what is happening in the snowpack.

Weather models started being useful for big scale processes and we can expect snowpack models to follow suit. Rather than treating virtual profiles as slope-specific information, we can use snowpack models to look at regional differences in snowpack structure. For example, a surface hoar layer may form in the northern Monashees but not the southern Monashees because a storm tracking along the U.S. border causes too much cloud cover for surface hoar to form. Current applications of virtual snow profiles can already resolve some of these big-scale patterns. A focus of the avalanche research group at Simon Fraser University is developing ways practitioners can visualize and understand these patterns. 

Weather models eventually grew from basic advisory tools to predictive powerhouses. A big reason they became more accurate in the 1980s and 1990s is they were fed with more observations of current atmospheric conditions. Uncertainties about the current weather (such as the initial conditions) is one of the main sources of errors in weather models. Over the past few decades, the amount of observations that could be collected by satellites, radars, and airborne sensors has exploded. Once the initial weather conditions are processed, computer models simply apply the laws of physics to figure out what will most likely happen next.

Similarly, the biggest source of uncertainty in snowpack models is figuring out when, where, and how much it snows. The most realistic virtual snow profiles are the ones at locations with good snowfall measurements or forecasts. Once snow is on the ground, the laws of physics do a pretty good job of figuring out how it evolves, but measuring and predicting snowfall is still hard, and even the best measurements and models currently fall short. We can expect to continue getting better at knowing how much it snows with better weather forecasts and observation networks. From there, we can get better at predicting the snowpack structure.

MERGING OLD AND NEW

LEFT: METEROLOGY SERVICES OF CANADA RADAR IMAGE OF WESTERN CANADA // MSC

RIGHT: WEATHER MAP FROM SCANDINAVIA FROM 1874 // WIKIPEDIA CREATIVE COMMONS

 Early weather models were considered advisory tools. Meteorologists would check their own jet stream forecasts against the computer forecasts to increase confidence in their predictions. Computer-based systems were brought into the loop to augment human capabilities rather than replace them. They were a thinking tool. What really changed the day-to-day operations of meteorologists was the development of tools that merged old methods with the new technology.

In the late 1990s, interactive computer dashboards were developed that allowed forecasters to visualize field observations, satellite imagery, and computer model forecasts all in one place. Bringing different sources of information together allowed forecasters to get the most complete picture, filter through all the information, and weight each type of data according to its strengths and weaknesses.

The InfoEx is a current example of a forecasting tool that helps us build an understanding of avalanche conditions based on field observations and analysis by fellow professionals. Perhaps a future version of the InfoEx could combine the information we currently use with satellite maps of avalanche debris and some fusion of a remotely-sensed and computer-simulated snowpack visualizations to give us a more complete picture of avalanche conditions. If designed effectively, such a tool should help us assess hazards faster, more efficiently, and more accurately.

There’s lots of talk about machine learning and losing work to automation. This is scary for a community that looks to the mountains for an escape from the chaos of the digitized world. These emerging technologies could change aspects of avalanche work, but they won’t automate it. The transformation of weather forecasting took decades, billions of dollars, and major international collaborations. Even with that, weather is (probably) still easier to predict than the delicate slope-scale processes that cause avalanches. Plus, meteorologists still have jobs—they just spend less time analyzing data and more time communicating and making decisions.

The hope is that integrating new technologies will improve our hazard assessments so we can focus our time and energy on risk mitigation. Computers are great at pattern recognition—better than humans in many fields—but thankfully avalanche forecasting is more than that. Computer predictions will need to be verified, interrogated, and interpreted by humans. Ultimately, the complex mitigation decisions are up to us. Field work may become more targeted, where the computer system identifies the greatest uncertainties that need to be resolved by sending field teams to answer specific questions.

There will certainly be a learning curve, perhaps a slow one, where we gradually learn what technology can offer. We should all be engaged to learn about how these technologies work and, more importantly, have our say on how they should be implemented so we can make informed decisions about the future of avalanche forecasting.

REFERENCES
Benjamin, S. G., Brown, J. M., Brunet, G., Lynch, P., Saito, K., and Schlatter, T. W., 2019. 100 years of progress in forecasting and NWP applications, Meteorological Monographs, 59, 13.11-13.67.

Eckerstorfer, M., Bühler, Y., Frauenfelder, R., and Malnes, E., 2016. Remote sensing of snow avalanches: Recent advances, potential, and limitations, Cold Regions Science and Technology, 121, 126-140.

Horton, S., Nowak, S., and Haegeli, P., in review. Enhancing the operational value of snowpack models with visualization design principles, Natural Hazards and Earth System Sciences.

Morin, S., Horton, S., Techel, F., Bavay, M., Coléou, C., Fierz, C., Gobiet, A., Hagenmuller, P., Lafaysse, M., and Ližar, M., 2019. Application of physical snowpack models in support of operational avalanche hazard forecasting: A status report on current implementations and prospects for the future, Cold Regions Science and Technology, 102910.

By Nadine Overwater

COMMON AVALANCHE AREA SIGNAGE TO PROMOTE WORKERS NOT TO STOP ON ACCESS ROADS IN AVALANCHE THREATENED AREAS.

THE PATCHWORK ARTISTRY OF FORESTRY; we’re all familiar with cutblocks and recognize that they are the visible signs of resource extraction, like mine sites, hydroelectricity and its structures, and transportation corridors which move both people and raw materials. The cutblock is smaller but can have an impact on slope stability or open the possibility of avalanches in terrain that was not previously susceptible. Do foresters recognize, pay attention and care about the implications of creating these openings and corridors and the possibility of new avalanche terrain that may affect the workers, public and the environment?

By law, forest professionals are required to consider aboriginal interests, species at risk, old growth retention, wildlife corridors and connectivity, migratory birds, species and ecosystem diversity, visual quality, forest health, wildfire mitigation, terrain stability; the list of parameters to be considered in land management is long and complex. In a rugged and mountainous landscape, a winter site visit to a newly harvested block makes it evident that avalanche hazard is clearly a factor that also needs to be considered.

There is no legislation that specifically requires a forest professional to consider the possibility of creating avalanche terrain when designing cutblocks. The Forest Planning and Practices Regulation (FPPR 4:1(37) requires that forest professionals must design forest development considering terrain stability, which may also be interpreted to include snow stability. There is also The Land Managers Guide to Snow Avalanches in Canada (CAA, 2002) which outlines methods for recognition and planning of avalanche terrain, a helpful publication but lacking the rule of law. Obligations may be partially captured in the bylaws governing the Association of BC Forest Professionals which cites criteria to uphold the public interest, and practice professional duties with
competency, integrity and due diligence. This means that the public has trust in forest professionals to be able to undertake their job with the knowledge required. Areas where crown infrastructure exists or may be placed at risk, for example above a highway, are placed in a category where a qualifi ed registered professional must complete an assessment to ensure the slope will not be problematic in the future. The Ministry of Transportation brokered this deal and is described in a technical bulletin Snow Avalanche Assessments: the basic facts (ABCFP, 2002).

HARVESTED CUTBLOCK THAT HAS MINIMAL ANCHORS LEFT ON SLOPE. IS THIS NOW A MAN MADE AVALANCHE PATH?

I am a forest professional who is directly responsible for cutblock and road design in the heart of the Columbia mountains both north and south of Revelstoke, BC. In my opinion, a strong knowledge of avalanche terrain is required to work in many parts of our province (BC). Opening up steep hillsides above roads not only poses a threat to public and employees travelling below, but it makes it difficult for the newly planted trees to establish when they are prone to slide activity and snow creep continuously acting on the seedlings. There is the consideration of downslope resources as well, which very often include fish habitat and/or standing timber. It does not benefit the licensee or the public to create cutblocks that are prone to sliding.

Despite the legislative gap that does not require their consideration, it is my hope that most forest professionals doing work in avalanche territory reflect on the creation of new avalanche hazard when designing roads and cutblocks. There are mitigative strategies as well, that can be implemented when steep slopes cannot be avoided. One of these strategies is leaving behind high stumps - well beyond the threshold snowpack levels. This method has been successful in anchoring the snowpack until a new plantation is established and avalanche hazard is removed. The only downfall of this method is the wasted timber, left behind as two metre stumps. Cutblocks that are designed to be longer across the slope but have shorter length upslope, minimize the mass and velocity of any potential avalanche. Avoiding existing avalanche paths and the trim vegetation (or forest) along edges and above or below existing paths, helps prevent the creation of larger avalanche paths.

The Columbia Valley typically experiences a deep snowpack and regular avalanche activity. For those of us who work here, we travel through the landscape as professionals and as recreationists, so our awareness of avalanches becomes a subconscious element in our design decisions. Do all forest planners consider the creation of new avalanche terrain? What about foresters in the Okanagan, where the snowpack reaches one metre on a good year? How are areas with drier climates and lower annual snowpack being considered at the planning phase? What about the compounding effects of wildfires opening up the forest landscape? Suppose they are hit with an extreme winter and higher than normal snowpacks. What then? It is highly probable that avalanche activity could occur in areas that have not previously seen this type of disturbance. Hopefully, a design flaw like this can be caught at the geotechnical analysis stage; many terrain instabilities are related to slope and if it is recognized that the ground can move, then it becomes obvious that what sits on the ground can also move (disregarding ground roughness).

A major concern and problem that is faced by many forest planners today is the fact that the resources are getting further into the valleys and further up the slope. The generations before us have taken the “cream of the crop” and accessible timber. We are now faced with developing land that consists almost entirely of steep slopes and cable harvesting. I am not certain that all forest professionals have the knowledge of avalanche behaviour to be able to develop this type of terrain moving forward. I think that there is room for professional development to ensure that we are designing sustainable and safe forest openings. An idea that can be jointly approached by professional foresters, geotechnical engineers and avalanche technicians.

MANY OF THE MOUNTAINS IN BRITISH COLUMBIA ARE BECOMING A PATCHWORK OF NATURAL AND MANMADE AVALANCHE CONCERNS.

Steep slopes are an obvious concentration point, but what about those lower angle slopes? A final thought, and something that I feel may not be approached by all forest professionals, is the unfortunate creation of surface hoar farms, those lively sections of terrain created by the development of low and mid elevation cutblocks in sheltered valleys. Frequently we see cutblocks on low angle slopes with signs of natural slab avalanches in them, mostly size one, that terminate close to where they initiated. It is difficult to avoid making these cuts, but it is a problem, nonetheless.

I’m uncertain if there are design measures that can be utilized to mitigate surface hoar farms, and because they are low consequence events, they do not necessarily appear on the radar of the forest professional hanging ribbons and traversing boundaries through waist deep brush in the summer months. It could also be a topic worth pursuing moving forward in the world of professional development.

This is a personal take on the intersections of forestry and the avalanche industry. I cannot speak for anyone other than myself. However, I do believe that we have been successful in managing cutblock design when it comes to the creation of new avalanche paths. When I am driving, touring, hiking or flying through our valley I don’t find myself looking at failed designs and appalling scenes of recurring avalanches where they have never been before. Yes, there is the odd one and yes, I believe that there is room for education and advancement, especially in the face of climate change.

I do know that as forest professionals, we are bound to forest management objectives that best serve the public and the environment and that snow and slope stability are considered directly or indirectly in the planning process.

LOG HARVESTING ON THE MOUNTAIN SIDE DURING THE WINTER SEASON.

REFERENCES
Canadian Avalanche Association. 2002. Land Managers Guide to Snow Avalanche Hazards in Canada. Jamieson, J.B., C.J. Stethem, P.A. Schaerer and D.M. McClung (eds.). Canadian Avalanche Association, Revelstoke, BC, Canada

ABCFP & APEGBC Joint Practices Board, May/June 2002. Technical Bulletin Snow Avalanche Assessments: the basic facts. Forum. https://member.abcfp.ca/
WEB/Files/publications/FORUM-2002-3_avalanche.
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avalanche.pdf

By Tony Webster, Adventure Guide Program, Thomson Rivers University

“Clients skiing untracked powder may be so deep in the throes of ecstasy that they fail to listen to directions.” Photo courtesy of Phil Johnston

What causes group polarization and risky shifts?
This is an important question for outdoor leaders to ponder. If there is good understanding of the cause of a risky shift, a group member/leader may be more likely to prevent it from occurring or to detect it when it does occur. Since the discovery of group polarization, group dynamicists have put forward a number of theories to attempt to explain why such shifts happen. These include illusory cultural norms, the diffusion-of responsibility theory, leadership theories, familiarization theory and value theories (Forsyth, 1990; Powter, 1998).

In the sphere of mountaineering, an example of an illusory cultural norm might be represented by an attitude of “we’re a team on the mountain, therefore we’ll live” (Powter, 1998). Humans are innately social beings and tend to feel more comfortable being part of a social group, a phenomenon known as the herding instinct (Tremper, 2001). This instinct may have served us well during evolution but it can be deadly in the mountains, especially in avalanche terrain. Another common perception trap that could be classed as an illusory norm is to bring our human culture into a non-human setting, in essence a form of cultural arrogance. As Tremper (2001) points out, “city thinking and mountain thinking are very different things... when we go into the mountains, [city skills], more often than not, are liabilities”. Most humans are culturally insensitive to the backcountry, unable to speak its language and unwilling to accept its culture. Every year humans suffer the consequences of such an attitude and many pay for it with their lives.

The diffusion-of-responsibility theory states that group members will be more likely to recommend a risky course of action because of the feeling that they have less personal responsibility for the negative consequences of such a decision within the group setting (Forsyth, 1990). Stated another way, it is easier for an individual to hide within the group when making contributions to group decisions – they can take greater chances because they feel they are less likely to be blamed. A few investigators have cast doubt on this theory though.

Leadership theories revolve around the notion that high risktakers tend to exercise more influence over group members due to their greater persuasiveness, confidence, assertiveness and involvement in the discussion (Forsyth, 1990). This theory may carry some weight but is undoubtedly an oversimplification. If an individual demonstrates excessive amounts of these qualities, his credibility will almost certainly be undermined. Several researchers have been unable to demonstrate that this leadership effect occurs.

The familiarization theory asserts that as individuals mull over problems with others, they become more familiar with the items; as familiarity increases, uncertainty decreases, creating a willingness to advocate more risky alternatives. This theory appears to tie in nicely with the point made above that group discussion is a critical element in producing a risky shift. This theory would also imply that individuals who are allowed to familiarize themselves with an issue while alone should demonstrate a risky shift but this has not been consistently found. Therefore, similar to the above theories, some doubt has been shed on whether this is a valid theory.

The most widely accepted theories to explain the cause of a risky shift revolve around the notion that risk taking is a cultural value in itself. The general idea is that people in our society value risk, and in the group situation most individuals want to appear to be willing to take greater risks than the average person in order to be able to enhance their status in the group. Group discussion is essential as it allows the individual to learn his relative standing in the group as a risk-taker. Studies have clearly shown that most people regard themselves as above average risk-takers (of course a statistical impossibility) and tend to exhibit feelings of admiration for others who are perceived as being greater risk-takers than themselves (Forsyth, 1990). These findings provide clear evidence that the underlying assumption of the value hypothesis is correct.

Group dynamicists have developed two schools of thought within this general approach (Forsyth, 1990). The “social-comparison” theory argues that group members are trying to accomplish two interrelated goals during discussions. First, they are attempting to evaluate the accuracy of their own position on the issue by comparing it with others and, second, they are trying to make a favourable impression with the group. The result is a tendency to describe one’s own position in more extreme terms. The “persuasive arguments” theory, in contrast, stresses the information obtained during discussion and asserts that if the individual is exposed to a persuasive argument, they are more likely to shift or move their own decision in that direction. Both of these theories have been supported by researchers and this has prompted several investigators to suggest
that the two processes combine to produce polarization.

Implications of the risky shift and practical issues for outdoor leaders
A key question to be addressed in this section is in what kinds of situations is a risky shift most likely to occur? Armed with this information, prevention, detection and/or management of the phenomenon becomes substantially easier. The answer will unfortunately never be clear-cut, as the operation of any group, even the smallest, is a complicated union of many factors. Powter (1998) discussed group dynamics in a number of common wilderness experience situations: the guided trip, the growth/challenge experience, the personal recreation experience and the expedition.

The guided trip has probably the simplest and clearest norms for the group concerned, ones that are common knowledge; the guide makes the decisions in virtually all situations and client involvement is a matter of the guide’s discretion. Democracy in this instance would defeat the client’s intent in hiring a guide - to be provided with a controlled experience. As there is, in theory, little discussion between guide and client about precise details of the guided experience, there should be little opportunity for a risky shift to emerge. Of course, there may be situations where a group might conceivably place some pressure on a guide to attempt to change or modify a decision, but the guide always has the final say in decision making and most guided clients will respect this fact.

The growth/challenge experience, such as those offered by Outward Bound, uses the wilderness as a classroom for both skills and self-learning (Powter, 1998). The experiential learning model used necessitates a certain degree of democratic empowerment of the student which increases the possibility of a risky shift. However, the leader/instructor makes the autocratic decision as to the level to which the students will be empowered to make decisions and exercise control. Therefore, similar to a guided trip situation, excessively risky decisions will likely not
be implemented. 

The personal recreation experience is a classic situation where leadership issues and group process norms are often not clearly defined. The situation can be very confusing for group members and emergent leaders, particularly if active and open communication is lacking. It can be democracy in its truest form – the “free-for-all” – but unfortunately this kind of scenario is precisely the one where the risky shift has the greatest chance of surfacing. Characteristics of group members that might further increase the chance of a risky shift occurring will be discussed further below.

The expedition is a situation where group dynamics become exponentially more complicated. As individuals have usually invested substantial time and money into such an experience, they have more to gain and more to lose and will be far more likely to fight for themselves. A paradox operates here: people on expeditions are usually strong independent individuals who often struggle with authority, but once on the expedition they are essentially in a controlled situation. Hardly surprisingly, tension often ensues and decisions may be clouded by this fact. The expedition leader is in a very delicate situation and must be sensitive to environmental and intra-group factors and prepared to be somewhat flexible with his/her leadership and decision-making style, depending on the situation. One could argue that risky shifts are more likely to occur on expeditions as individuals are often prepared to take greater risks to achieve their goals/dreams. However, this would be pure conjecture as there are a multitude of factors involved that are in a high state of flux.

It has been established, then, that the personal recreation trip, and the corresponding democratic decision-making process that tends to accompany it, is prime breeding ground for a risky shift. What are some further group characteristics within this situation that might influence the emergence of excessively risky decisions? Some factors that may come into play include size of the group, gender, age, personality, skill ability, cultural origin and mood of the group members.

Though little information could be found in the literature about the affect of group size on a risky shift, the topic deserves some attention. If one accepts some of the theories presented above regarding the possible causes of group polarization, it would seem reasonable to speculate that risky shifts may be more likely to happen in larger groups than smaller groups. Imagine a scenario where a small group of two individuals are deciding whether to ski a questionable snow slope versus the same situation but with a group of six individuals. Humans tend to feel safer when in larger groups and also there is a greater chance that someone in a larger group may have a more extreme view that might influence the group’s decision. Intuitively, one might deduce that there is a greater chance of a risky shift with more group members. It is unlikely, however, that the chances of group polarization will continue to increase with increasing group size. Presumably, a point will be reached where the democratic decision-making process will be “bogged down” by the increasing numbers involved. The affect of group size on the emergence of a risky shift in the outdoor setting would be an interesting area for future research.

There are vast amounts of scientific research that suggest that males are greater risk-takers than females (Wilde, 1994), a trait that likely has both physiological (hormonal) and social roots. Numerous accident statistics support this assertion. For example, in the period 1984-1996 in Canada, 90% of avalanche fatalities were male (Jamieson & Geldsetzer, 1996). In addition, the age category with the greatest fatalities was 20-29 (just under 30%). This agrees with research that has consistently shown that young individuals show greater proclivity for risk than later years. Therefore, it appears that young males may be particularly susceptible to a risky shift.

Undoubtedly, there is truth to the statement, “Know the male yet keep to the female”! (Lao-tsu). Tremper (2001) states that, “I like to go into the mountains with women. I feel like I’m safer when I do. When I am out with my male friends, I know that I have to keep a sharp eye out for competition, pride and all the other traits that tend to go along with groups of men, because I’m often the worst of the bunch.”

Risk-takers also tend to be more competitive, aggressive, type A personalities than non risk takers (Begum & Ahmed, 1986) – “sensation seekers” as they are often called. A further finding that has emerged from avalanche accident statistics is that victims are often skilled in the activity (skiing, snowboarding, snowmobiling, etc) during which they suffered the accident (Tremper, 2001). It is likely that overconfidence in one’s skills “spills over” into one’s decision making regarding hazard and terrain assessment.

Some interesting findings have emerged regarding cultural origin and risk taking. It appears that male Caucasians of western origin are amongst the most “risk prone” individuals. Hong (1978), in a comparison of Chinese and American students, found that cautious shifts were far more likely in the former and risky shifts were far more likely in the latter. As discussed above, this is likely related to the value that risk carries in the Western culture as opposed to Asian cultures.

Finally, the influence of mood on group decision making and risky shifts is of importance and must be recognized. Heli-skiing guides are very aware of the euphoria phenomenon – clients skiing untracked powder may be so deep in the throes of ecstasy that they fail to listen to directions. Also, it is known that most avalanche accidents occur on the sunny days following a large snowfall when people are likely too busy enjoying themselves to pay attention to the hazards around them (Tremper, 2001).

“Summit fever” is another example – becoming fixated upon a goal at the expense of sound decision making. Negative moods, however, may also cause risky shifts. Take the scenario of a group of hungry, cold and wet hikers in foul weather who want to get home at the end of the day. The tendency will be for the group to rush decisions and cut corners which could have serious consequences. Just when they most need to pay attention, the weather and their mental state has pushed them to do the opposite.

Summary & Conclusions
Most outdoor enthusiasts and hopefully all outdoor leaders understand the importance of respecting objective hazards in the backcountry. There appears to be less appreciation for some of the more subtle subjective hazards associated with group members and group dynamics, yet these are no less important to understand. The risky shift is an example of such a hazard.

In the outdoor setting, risky shifts are most likely to occur on a personal recreation trip where the group members consist of young, competitive and enthusiastic Caucasian males who perceive that they are highly skilled in the activity in which they are engaged. The risky shift is one of many cognitive factors that can contribute to poor safety decisions in the outdoors, including lack of experience, inappropriate attributions, inattentiveness, “smelling the barn” and simply poor judgment (Priest & Gass, 1997). The importance of active and open communication amongst group members as a form of hazard avoidance cannot be underemphasized. If excellent communication combined with a deeper understanding of subjective hazards were a major priority for all groups involved in outdoor pursuits, there would undoubtedly be less accidents and fatalities annually in the wilderness.

References:
Begum, H.A. & Ahmed, E. (1986). Individual risk taking and risky shift as a function of cooperation-competition proneness of subjects. Psychological Studies, 31: 21-25.

Forsyth, D.R. (1990). Group Dynamics (2nd Edition). Pacific Grove, CA; Brooks/Cole Publishing.

Hong, L.K. (1978). Risky shift and cautious shift: some direct evidence on the culture-value theory. Social Psychology, 41: 342-346.

Jamieson, B. & Geldsetzer, T. (1996). Avalanche Accidents in Canada. National Research Council of Canada: Canadian Avalanche Association.

March, B. (1998). Adventure and risk. In: Toft, M (Ed). Playing it Safe – Selected Mountain Leadership Papers, Techniques and Test Reports of the Alpine Club of Canada. p.7-11. Calgary, AB: McAra Printing.

Myers, D.G. & Lamm, H. (1976). The group polarization phenomenon. Psychological Bulletin, 83: 602-627.

Powter, G. (1998). Group dynamics from a leadership perspective. In: Toft, M (Ed). Playing it Safe – Selected Mountain Leadership Papers, Techniques and Test Reports of the Alpine Club of Canada. p.29-43. Calgary, AB: McAra Printing.

Priest, S. & Gass, M.A. (1997). Effective Leadership in Adventure Programming. Champaign, IL: Human Kinetics.

Shaw, M.E. (1976). Group Dynamics: The Psychology of Small Group Behaviour. New York: McGraw-Hill.

Tremper, B. (2001). Staying Alive in Avalanche Terrain. Seattle, WA; The Mountaineers.

Wilde, G.J.S. (1994). Target Risk. [On-line]. http://psyc.queensu.ca/target/index.html

Figure 1: Using basic equipment, the researchers worked to replicate a small sample of what nature does in incredible variety—make surface hoar.

The Experiment
On July 14, jumping head first into the experiment, we decided to do the intuitive thing; boil water, move it into the cold lab, trap it with a plastic container and simply let the natural phenomenon of self assembly take the reins. You can see the simple apparatus consisting of a pot of boiling water, a steel paint strainer, and two plastic paint strippers in Figure 1, all to be covered by a plastic bin. The apparatus was not sophisticated; there was no delicate thermocouple wires dedicated to providing temperature readings or expensive gadgets measuring relative humidity, yet, it was successful. After leaving it overnight in a dark cold lab, devoid of sky view and significant air flow, tiny ice sculptures appeared on the underside of the steel paint strainer.

At different temperatures there would be, inevitably, different formations occurring. Plates formed at an ambient cold lab temperature of -7 ºC (Figure 2), while needles and feathery structures formed at -12 ºC and -13 ºC (Figure 3). A transition zone producing stretched plate structures was also observed from -9 ºC to -11 ºC. To give you an idea of size, the plates measure on the scale of a few millimetres while the needles grew to a maximum of one centimetre.

Figure 2

Here’s how we thought it would work, in theory. The air trapped under the bin would soon become saturated and condense around the equipment. As the steel paint strainer cooled with its surroundings, the condensation began to freeze around its edges, creating a good base for surface hoar growth. However, this is not exactly what happened. There was an inconsistency in the temperature. Outside the bin was cold (sometimes down to -13ºC). Inside the bin the air was kept warm from the hot pot of boiling water. In the same way our body reacts to cold, the extremities of the experiment cooled first, and because the edges of the bin were the first to reach freezing temperatures, vapour molecules began moving away from our nicely laid out landing pad and towards the plastic bin. The unruly vapour collected itself onto the unintentional surface, forming a less interesting layer of frost.

While humidity is an important factor in the formation of surface hoar it is not the only cause of crystal growth. Wind and sky view are two other contributors to their growth. If humidity were the only factor, we would have seen a more uniformly spread collection of crystals. Instead, the crystal growth was concentrated near the openings between the paint strippers and the edge of the pot, growing towards the vapour source. By positioning the paint strippers in a way that constricted steam flow through the strainer (Figure 1), an environment offering saturated air flow was created.

Conclusion
The imitation hoar grew under different circumstances and through a different process than natural surface hoar crystals. Simply put, natural surface hoar is formed when the snow surface cools enough at night to attract nearby water vapour molecules from the air. The imitation surface hoar grew because of highly saturated air flow. Our questions about the relationship between sky view and crystal growth still remain, as new questions were generated on the underlying physical processes governing the phenomenon of self-assembly. Perhaps this small experiment created more questions than it answered.

Now, after wrapping up the project and heading back to university, I still think about how to improve the experiment for future trials. Maybe I can try different surface materials such as natural snow, a different set up, or a different procedure. What factors can be controlled and manipulated other than temperature and what will be the result? When starting the experiment I wasn’t sure whether any relevant results would be possible. Ice and frost were a given, but surface hoar? I wasn’t sure. After observing the outcome, I wonder if this is the beginnings of a new way to study surface hoar formation and what it might mean to practitioners in the future.

Figure 3

Acknowledgements:
Thanks to everyone involved, including all members of ASARC. Specifically, thanks to Cora Shea and Bruce Jamieson for all of their advice. Thank you to the Civil Engineering Department staff at Schulich School of Engineering who provided all the necessary equipment. I would not have been able to do this without the help of Terry Quin.

Reference:
Shea, C. and B. Jamieson. Predicting surface hoar spatial variability in sparse forests using shading in satellite imagery, International Snow Science Workshop, Swiss Federal Institute for Forest, Snow and Landscape Research WSL., Davos, Switzerland, p.102-106 (2009)

By Wren McElroy

An AST instructor discovers some striking similarities between staying alive in avalanche terrain and staying alive in Afghanistan.

Smiling soldiers with their civilian instructors Wren McElroy and Keyes Lessard.

 1 Combat Engineer Regiment—the privates, the sappers. These are the young men and women who fight in the Canadian Army. Most of this group has been to Afghanistan and some will go back on another tour of duty soon.

On a two-week training session in Trail BC, this Edmonton-based regiment took an AST 1 course in preparation for the Olympics. They won’t be visible at Whistler Village or any high-profile events; they will more likely be patrolling the surrounding mountains ensuring no danger threatens the games. They know how to be close to danger. These young people are the ones we hear about on the evening news, when a report is read of yet another Canadian soldier killed.

As I write this, news comes again that the 108th Canadian soldier has been killed in Afghanistan, this one a 25-year old sapper, a Combat Engineer who hit a roadside bomb. During the evening classroom session, while I was explaining the waivers for the course, one of the soldiers said, “Ma’am, we’ve been to war.” Right. These people know about risk.

What this group didn’t know about was avalanches. Keyes Lessard, CAA Professional Member and Instructor with Selkirk Colleges Renewable Resources Program and I spent two days at Kootenay Pass with this group to help prepare them. What struck me and inspired me was how similar some of our collective experiences were. At first glance one wouldn’t think so. How could you compare skiing powder in the Kootenays to combat conditions in Afghanistan at 60° Celsius? One has cold smoke to choke on. The other has fine silt-like dust invading the eyes and lungs. What we did have in common was exposure to risk.

I was very impressed with how well these soldiers assimilated the information presented. In the classroom we did an exercise to go over the steps of avalanche rescue. Splitting the soldiers into three groups we gave each group a small bag with the steps for self rescue, companion rescue and organized rescue. Each step was cut out and their job was to put the steps in the correct order. With their experience in order and prioritizing it was an easy task.

After signing out rescue gear on Saturday morning at Kootenay Pass, we headed across the highway to the Ministry of Transportation compound where MOT Avalanche Technician Robb Andersen and his CARDA dog Aquillo met us. A happy soldier volunteered to climb into a snow cave and be blocked in while he waited for Robb to give Aquillo the signal to start the search. Within minutes Aquillo was digging at the entrance of the cave ready for her reward—a game of tug-o-war.

The engineers described arriving in Afghanistan and, with no previous training or introductions, being assigned a dog team for sniffing out explosives. This group is very well adapted to learning on the fly, yet they appreciated the opportunity to see an avalanche dog at work and get an understanding of the needs of the dog handler. Robb answered all of their questions while Aquillo happily sniffed all of the green camo.

Probing avalanche debris, or probing for land mines. Which would you rather do?

In the field, as we taught them how to do transceiver searches, they spoke of how they trust their equipment, and how they felt confident with the new skills. While we discussed and practiced spiral probing, they described “prodding” for land mines, which they do with a one-metre prod while they inch along on their belly. The same spiral technique is used when looking for hazards while searching a house, building or an area of land.

When it came to digging the snow profile they happily exclaimed, “Now this we are good at—digging!” They also commented on how much easier digging in the snow is than digging trenches. As we traveled higher on Cornice Ridge on the south side of Kootenay Pass, we stopped to discuss how they would handle travelling through the avalanche paths, cliffs, trees and gullies. One soldier described the use of “tactile exposure”—staying out of view of the enemy. He pointed out that he would travel just inside the trim line of the path to stay out of the line of fire. Once they began to appreciate the destructive force of an avalanche, they all agreed they would increase their safety margin and travel further into the mature timber.

On day two as we sat down for lunch I asked the question that had been on my mind while working with this group. Did they know any of the soldiers who had been killed in Afghanistan? A few of them did. As we talked of the trauma they had seen, it made me think of my own experience in avalanche rescues and of friends I had lost in the outdoors. The causes were very different but the impact of the trauma was the same. This was just one more crossover between our professions.

The ability of these soldiers to adapt to a new environment and incorporate information was inspiring. The hardest thing for this group to deal with was the 30-or 40-year-old aluminum beavertail snowshoes, without teeth. The snowshoes would work fine in the prairies but they were certainly not designed for mountain travel. This fact we quickly discovered as we started to descend on a sun-crusted southerly aspect. The group appreciated traversing around to the north aspect and descending through the much softer crystalline surface hoar. The other option they had for travel were equally outdated cross-country skis they would strap in with their mukluks. It would be a lot easier for these soldiers to travel through the mountains with real ski equipment.

These combat engineers showed a high level of professionalism that made the course a pleasure to teach. When I spoke with their officer in charge, Lt. Mary Benjamin, after the course, she described the soldiers as being excited about their experience and bragging to their comrades that they knew what facets were. This group is hoping to get more training in preparation for the Olympics. Maybe we can get them through the newly developed SAR Level 1 program before February 2010.

Scott Thumlert¹, Grant Statham², Bruce Jamieson³
1 Alpine Solutions and Canadian Mountain Holidays - corresponding author

2 Parks Canada and Alpine Specialists

3 Snowline Associates Ltd.

“EVEN IF AVALANCHE FORECASTING IS PROBABILISTIC AND INCLUDES UNCERTAINTY, IT SHOULD BE GROUNDED IN CLEAR DEFINITIONS, AND UNCERTAINTY SHOULD NOT STEM FROM NEBULOUS TERMS BUT THE NATURE OF THE PROBLEM.” – JÜRG SCHWEIZER (SCHWEIZER ET AL., 2019).

TWO YEARS AGO, nine of us gathered before breakfast to plan for the day of helicopter skiing ahead. We aimed to talk about the weather, flying conditions, avalanche hazard, and the run list, except there was an argument about the avalanche hazard forecast. Specifically, what likelihood term should be used to assess the persistent slab problem for the day: “possible” or “unlikely.”

The argument wasn’t serious and only resulted in two angry guides and seven frustrated guides wondering how we wasted so much time. Later, I asked the angry guides what they thought the terms “possible” and “unlikely” meant in terms of probability. Guide one said, “Unlikely is about 5%.” Guide two said, “Possible is about 5%.” Their interpretations of “possible” and “unlikely” were exactly the same! The argument was pointless.

The Conceptual Model of Avalanche Hazard (CMAH) (Statham et al., 2018) has been widely adopted in North America as a systematic, risk-based workflow for avalanche forecasting and, in my humble opinion, is a huge achievement for our industry. Now that the model has been in use for several years, we have the opportunity to explore how it is working in the field and look at how well modern risk terminology works for avalanche forecasting. Based on the above story, and many similar ones, a few of us have been wondering what the words used to describe Likelihood of Avalanche(s) actually mean to practitioners as probabilities.

AVALANCHE PRACTITIONER SURVEY

We asked avalanche practitioners from around the world (75 responses) to put a percentage number beside each of the likelihood words from the CMAH (unlikely, possible, likely, very likely, and almost certain) for what they interpreted the words to mean about the probability of avalanches. Figure 1 shows the results.

We observe distinct median values that are similar to forecasting experts in other industries (e.g. Beyth-Marom et al., 1982; Clarke et al., 1992; Reagan et al., 1989). However, we also observe a very large range in probabilities associated with the likelihood terms, and perhaps most importantly, we observe large overlap between categories with average practitioner estimates for “possible” ranging from 2-55% and “unlikely” from 0-35%. This is alarming and it’s not hard to imagine a communication problem developing if one practitioner thinks 5% for “possible” and another uses 35% for “unlikely.”

FIG. 1: PROBABILITY INTERPRETATIONS FROM PROFESSIONAL AVALANCHE WORKERS ASSOCIATED WITH WORDS USED TO FORECAST THE LIKELIHOOD OF AVALANCHE(S) (CMAH), WITH MEDIAN VALUES SHOWN AS DASHED LINES.

DISCUSSION OF SURVEY

While this large range and overlap is startling and potentially challenging to work with, it is not altogether surprising. There is a depth of research that has consistently found verbal descriptions of uncertainty, such as “unlikely,” are interpreted differently by different people and also differ widely for the same people in different contexts (e.g. Nakao et al., 1983; Theil, 2002; Morgan, 2017). Are there reasons specific to our industry for the large range and overlap in estimates from avalanche practitioners?

1. Likelihood of Avalanche(s), as defined in the CMAH, results from a combination of “sensitivity to triggers” and “spatial distribution” and has not yet been explicitly defined in terms of numerical probability ranges, meaning avalanche practitioners do not yet have training or guidance on what probabilities we should use for forecasting avalanches.

2. Natural and human-triggered avalanches are rare (e.g. Schweizer et al., 2019), so the experienced-based probabilities from practitioners are likely lower than what many people commonly associate with the likelihood words. Hence, some practitioners provided probabilities for actual human triggered and natural releases (low values), whereas some provided the more common numbers associated with likelihood words (higher values), which contributed to the large range.

3. The reference definition for Likelihood of Avalanche(s) in the CMAH is dependent on the forecast’s spatial scale. It states “Likelihood of Avalanche(s) is the chance of an avalanche releasing within a specific location and time period, regardless of avalanche size.” The likelihood of a single wind slab releasing within the entire North Columbia region will be much higher than the likelihood of a single wind slab releasing on Mt. Rundle.

Discrepancy between interpretations of likelihood expressions has been shown to create communication problems (Fischer and Jungermann, 1996). It can reduce forecasting accuracy (e.g. Rapoport et al., 1990) and ultimately compromise decision making (Friedman et al., 2018). In a classic example, in 1961 during the Cold War, John F. Kennedy asked his Joint Chiefs of Staff to evaluate the planned Bay of Pigs invasion. They assessed the probability of success to be about 30% and communicated that as, “The plan has a fair chance of success.” Kennedy interpreted “fair chance” as favourable odds and approved the operation, which ended in stunning defeat. The Joint Chiefs later reported, “We thought that other people would think ‘fair chance’ would mean ‘not too good.’” The varying interpretations of “fair chance” was the key misunderstanding of the entire project (Wyden, 1979).

Other industries have been working on this problem and have developed strategies we can learn from and potentially adopt. For example, the Intergovernmental Panel on Climate Change (IPCC) has been desperately trying to figure out how to communicate the risks of climate change to the public and policy makers (e.g. Budescu et al., 2014); meteorologists have been promoting the use and communication of probabilistic weather forecasts (e.g. Fundel et al., 2019); and the intelligence industry has developed standards for expressing uncertainty and confidence in judgments (e.g. IDC 203, 2015).

STRATEGIES

Can we incorporate strategies developed by other industries to help with risk communication and forecasting for avalanches? First, we have to make some underlying assumptions:

1. Natural or human-triggered avalanches are relatively rare. Jamieson et al. (2009) estimated the odds of a human triggering a potentially fatal avalanche at considerable danger, skiing one start zone, and “without skilled route selection” between 1:100 and 1:1,000. These odds change by orders of magnitude with varying levels of avalanche hazard. Further, accident data show the risk from natural avalanches is about 10% of the risk from human triggering (Tremper, 2008). Translating these rough odds of encountering a dangerous avalanche into probabilities equates to 0.1-1% for human triggering and 0.01-0.1% for natural releases at considerable danger. For comparison, let’s compare the results from this survey to the North American Public Avalanche Danger Scale (Statham et al., 2010a): “Natural avalanches possible (practitioner estimate = 30%); human-triggered avalanches likely (practitioner estimate= 60%).”

2. Associating probability numbers with likelihood terms improves risk communication (e.g. Budescu et al., 2009; Budescu et al., 2012). Further, explicitly combining the term with the intended numerical range is more effective than having a separate descriptive table (Wintle et al., 2019). Writing “good chance (10-30%) of avalanche release” is more effective than having a separate table describing the 10-30% range for “good chance.”

3. Using frequency statements greatly improves understanding of probabilities and ensures the reference scales are defined (Gigerenzer and Edwards, 2003). For example, a frequency statement for a “20% chance of avalanches” could be translated to “20 out of every 100 avalanche paths.”

Using these assumptions, we propose some ideas for development of the Likelihood of Avalanche(s) scale used to forecast avalanches. It is critical to understand these ideas are provided with the intention of improving risk communication for field decisions, and not to transition avalanche forecasting to numerical calculations.

Limitation statement: these concepts should be interpreted only as ideas for future development and we present them only with the intention of providing an example of what another scale could look like, and to inspire debate, conversation, and further research.

Here are three ideas that have potential to improve risk communication for avalanche work:

1. Consider this definition for Likelihood of Avalanches. Please read carefully: Consider ANY avalanche path in the forecast region where the specified avalanche problem type is expected to exist. Likelihood of Avalanches is the chance of those avalanche paths releasing within the forecast time period, regardless of avalanche size.

For example, PERSISTENT SLABS – BTL (below 1,900 m) on ALL ASPECTS, what is the chance of those paths releasing naturally or from human triggering?

This definition includes the relevant spatial scale: any potential avalanche path. It automatically adjusts to whatever spatial scale is forecasted for. It also allows the translation of probability into frequency descriptions. For example, “Persistent Slabs - Good Chance (10-30%) to size D3” would translate to, “On average 10-30 out every 100 potential paths will release deep slab avalanches.”

2. Associating numerical probability ranges for each word in the scale that are more closely aligned with the underlying rates of avalanche release probability. These probability ranges will be much lower than the results of the survey, and more similar to other natural hazards (e.g. Porter and Morgenstern, 2013). We propose numerical ratings that increase by a half order of magnitude in Table 1. As better data emerge for natural and human-triggered avalanche release rates, these probability ratings can and should evolve.

3. Using chance terms to describe the probability of avalanches as these words are more intuitively associated with lower probabilities. As evidenced in the survey results and literature, likelihood words are already commonly interpreted with underlying probabilities that are much higher than actual avalanche releases. Thus, we need words that can be easily associated with these lower probabilities for use by people working in the field. For example, it is not intuitive for most people to use the word “likely” with a probability of less than 50% (Mauboussin and Mauboussin, 2018). Suggestions are provided in Table 1.

APPLICATION

TABLE 1: PROPOSED SCALE DESCRIBING THE LIKELIHOOD OF AVALANCHES.

Table 1 offers forecasters a very different way of evaluating the Likelihood of Avalanches based on estimates of either avalanche frequencies or probability. When forecasters are evaluating a particular avalanche problem, they might (for example) imagine 100 avalanche paths typical to their area that could produce this type of avalanche and then estimate how many of these paths they think will release, both naturally and with human triggers. While the frequency estimate works for areas with many paths, it’s not so useful when evaluating single paths or areas with only a few paths. In these cases, the subjective probability estimates or the chance terms are more appropriate.

INTEGRATION WITH FORECASTING

How would this Likelihood of Avalanches scale combine with avalanche size to produce a hazard rating? Figure 2 shows a potential method to be used as a suggestion or starting point for the hazard rating (after Muller et al., 2016a; Clark and Haegeli, 2018). It should be adjusted by expert judgment as deemed appropriate. More specifically, expert judgment is very much required to combine the various avalanche problem types that may be present in the snowpack into the hazard rating.

FIG. 2: GUIDANCE FOR COMBINING LIKELIHOOD OF AVALANCHES WITH AVALANCHE SIZE TO ASSIGN AVALANCHE HAZARD RATINGS (AFTER MULLER ET AL., 2016A; CLARK AND HAEGELI, 2018).

CONCLUSION AND FUTURE RESEARCH

The surveyed data from avalanche practitioners showed wide variation in interpretation and use of likelihood terms when forecasting avalanches. Differing interpretations of likelihood terms has been shown to reduce forecasting accuracy and compromise decision making, thus we present ideas for improving risk communication when forecasting avalanches (Table 1 and new definition for the Likelihood of Avalanches).

We suggest these and any other terms used in the future should reflect underlying data for avalanche release probabilities. As an example, the important paper by Schweizer et al. (2019) attempts to establish the relationship between avalanche occurrence and the avalanche danger level. We strongly encourage future studies like this with robust avalanche occurrence datasets to better define probabilities of avalanche release.

REFERENCES

Beyth-Marom, R., 1982. How probable is probable? A numerical translation of verbal probability expressions. J. Forecast. 1: pp. 257-269.

Budescu, D., Broomell, S., Por, H., 2009. Improving Communication of Uncertainty in the Reports of the Intergovernmental Panel on Climate Change. Psych. Sci. 20: pp. 299-308.

Budescu, D., Por, H., Broomell, S., 2012. Effective Communication of Uncertainty in the IPCC Reports: A Nationally Representative Survey. Climatic Change 113: pp. 181-200.

Budescu, D., Por, H., Broomell, S., Smithson, M., 2014. The interpretation of IPCC probabilistic statements around the world. Nature Climate Change. DOI: 10.1038/NCLIMATE2194.

Clark, T., Haegeli, P., 2018. Establishing the link between the conceptual model of avalanche hazard and the North American public avalanche danger scale: Initial explorations from Canada. Proceedings International Snow Science Workshop, Innsbruck 2018: pp. 1116-1120.

Clarke, V., Ru n, C., Hill, D., Beamen, A., 1992. Ratings of orally presented verbal expressions of probability by a heterogeneous sample. J. Appl. Soc. Psychol. 22: pp. 638-656.

Fischer, K., Jungermann, H., 1996. Rarely occurring headaches and rarely occurring blindness: Is rarely = rarely? The meaning of verbal frequentistic labels in specific medical contexts. J Behav Decis Mak. 9:153–72.

Friedman, J., Baker, J., Mellers, B., Tetlock, P., Zeckhauser, R., 2018. The Value of Precision in Probability Assessment: Evidence from a Large-Scale Geopolitical Forecasting Tournament. International Studies Quarterly, Volume 62, Issue 2, June 2018: pp. 410–422. https://doi.org/10.1093/isq/sqx078

Fundel, V., Fleischhut, N., Herzog, S., Gober, M., Hagedorn, R., 2019. Promoting the use of probabilistic weather forecasts through a dialogue between scientists, developers and end‐users. Quarterly Journal of the Royal Meteorological Society. https://doi.org/10.1002/qj.3482

Gigerenzer, G., Edwards, A., 2003. Simple tools for understanding risks: from innumeracy to insight. BMJ 2003; 327:741. doi: https://doi.org/10.1136/bmj.327.7417.741.

Intelligence Community Directive 203, 2015. Analytic Standards. Office of the Director of National Intelligence United States of America.

IPCC: Mastrandrea, M., Field, C., Stocker, T., Edenhofer, O., Ebi, K., Frame, D., Held, H., Kriegler, E., Mach, K., Matschoss, P., Plattner, G., Yohe, G., and F., Zwiers, 2010. Guidance Note for Lead Authors of the IPCC Fifth Assessment Report on Consistent Treatment of Uncertainties. Proceedings from IPCC meetings at Jasper Ridge, CA, USA.

Jamieson, B., Schweizer, J., Shea, C., 2009. Simple Calculations of Avalanche Risk for Backcountry Skiing. Proceedings International Snow Science Workshop, Davos 2009: pp. 336-340.

Porter, M., Morgenstern, N., 2013. Landslide Risk Evaluation: Canadian Technical Guidelines and Best Practices related to Landslides: a national initiative for loss reduction. Geological Survey of Canada, Open File 7312, 21.doi:10.4095/292234.

Mauboussin, A., Mauboussin, M., 2018. If you say something is “likely”, how likely do people think it is? Harvard Business Review. https://hbr.org/2018/07/if-you-say-something-is-likely-howlikely-do-people-think-it-is

Muller, K., Mitterer, C, Engeset, R., Ekker, R., Kosberg, S., 2016a. Combining the Conceptual Model of Avalanche Hazard with the Bavarian Matrix. Proceedings International Snow Science Workshop, Breckenridge, Colorado, 2016: pp. 472 – 479.

Nakao, M., Axelrod, S,. 1983. Numbers are better than words, Verbal specifications of frequency have no place in medicine. The American Journal Of Medicine. 74(6):1061–5. PMID: 6859055.

Rapoport, A., Wallsten, T., Erev, I., Cohen, B., 1990. Revision of opinion with verbally and numerically expressed uncertainties. Acta Psychologica. 74: pp. 61–79. https://doi.org/10.1016/0001-6918(90)90035-E 000169189090035E.

Reagan, R., Mosteller, F., Youtz, C., 1989. Quantitative meanings of verbal probability expressions. J. Appl. Psychol. 74: pp. 433-442.

Schweizer, J., Mitterer, C., Techel, F., Stoffel, A., Reuter, B.: On the relation between avalanche occurrence and avalanche danger level, The Cryosphere Discussions. https://doi.org/10.5194/tc-2019-218, in review, 2019.

Statham, G., Haegeli, P., Birkeland, K., Greene, E., Israelson, C., Tremper, B., Stethem, C., McMahon, B., White, B., Kelly, J., 2010a. The North American public avalanche danger scale. Proceedings of the 2010 International Snow Science Workshop, Squaw Valley, CA: pp. 117–123.

Statham, G., Haegeli, P., Greene, E., Birkeland, K., Israelson, C., Tremper, B., Stethem, C., McMahon, B., White, B., Kelly, J., 2018. A Conceptual Model of Avalanche Hazard. NatHazards 90: pp. 663–691. https://doi.org/10.1007/s11069-017-3070-5.

Theil, M., 2002. The Role of Translations of Verbal into Numerical Probability Expressions in Risk Management: A Meta-Analysis. Journal of Risk Research 5 (2): pp. 177–186.

Tremper, B., 2008. Staying Alive in Avalanche Terrain, 2nd edition. The Mountaineers Books, Seattle, Washington, USA: pp. 15.

Wintle, B., Fraser, H., Wills, B., Nicholson, A., Fidler, F., 2019. Verbal probabilities: Very likely to be somewhat more confusing than numbers. PLoS ONE 14(4): e0213522. ttps://doi.org/10.1371/journal.pone.0213522

Wyden, P., 1979. Bay of Pigs: The Untold Story. New York: Simon and Schuster

By John G. Woods, Wildvoices Consulting, Revelstoke

 On behalf of The Land of Thundering Snow Virtual Exhibit Project

ON OCTOBER 4, 1957, PEOPLE ACROSS CANADA AND AROUND THE WORLD LEARNED THE RUSSIAN WORD “SPUTNIK” WHEN THE SOVIET UNION LAUNCHED THE FIRST MAN-MADE SATELLITE INTO ORBIT. IN RECOGNITION OF THIS MOMENTOUS ACHIEVEMENT, THE NEWLY-ESTABLISHED AVALANCHE SAFETY TEAM WORKING IN ROGERS PASS THAT WINTER NAMED A SLIDEPATH ALONG THE PROPOSED ROUTE OF THE TRANS-CANADA HIGHWAY SPUTNIK 1.

FIG. 1: PLAN (PART) SHOWING AVALANCHE ACTIVITY DURING THE WINTER OF 1957-58 IN ROGERS PASS. NOTE THE ACTIVITY OF “SPUTNIK 1” SLIDEPATH ON JANUARY 8, 1958 // REVELSTOKE MUSEUM AND ARCHIVES

THE TRANS-CANADA Highway was under construction over Rogers Pass at the time and Sputnik 1 appeared on avalanche observation plans of the day (Fig. 1). Since a snowshed was planned for the highway across this slidepath, Sputnik 1 was the name used on the earliest construction documents for Canada’s first snowshed on a public highway.

Peter Schaerer was in charge of the avalanche survey crew that winter and describes the naming process in detail: “The crew of the Department of Public Works who observed avalanches and the weather in Glacier National Park in 1956-1960 was assigning names to the avalanche paths in 1957. The three major avalanche paths at Mount Tupper had been designated as Tupper No.1, No.2, and No.3 (actually, the idea popped up—but was abandoned—to rename them with the first names of the wives and girlfriends of the crew members). Because the name Sputnik was in everybody’s mind, we called the smaller avalanche path west of Tupper 1 “Sputnik No.1” and the path between Tupper 2 and Tupper 3 “Sputnik No.2.” The names were appropriate, because both paths were satellites of larger paths…” (personal communication, Schaerer-Woods, 2013).

The next year, after the United States launched their “Pioneer” rocket towards the Moon, the names of both the slidepath and the snowshed were changed to recognize this North American accomplishment. While the Rogers Pass avalanche atlas still includes the Pioneer slidepath (Schleiss, 1989), more experience during winter operating conditions resulted in connecting Pioneer and Tupper 1 sheds. The combined structure became the shed now called Tupper 1.

Pioneer Shed (a.k.a. Sputnik 1) was chosen as the site for the first snowshed because it was designed to be a relatively short shed—a good project to launch construction on what would become a suite of sheds protecting Rogers Pass’s eastern flank. This proved to be an excellent idea affecting the designs of all the subsequent sheds.

The ARMCO construction company won the contract to build this first shed and decided to use metal culverts supplied in multiple steel plates (Fig. 2). Unfortunately, the backfilling required to provide an even pressure distribution across the plates could not be completed by the first winter, and avalanches moved the structure out of position. The federal Department of Public Works lost confidence in metal designs and all subsequent snowsheds in the Pass were made of concrete (personal communication, Schaerer-Woods, 2013).

FIG. 2: PIONEER (A.K.A. SPUTNIK 1) SNOWSHED UNDER CONSTRUCTION IN 1961 // REVELSTOKE MUSEUM AND ARCHIVES PSS. 67

While the locations and designs of avalanche defences make use of the best available data on historic slide activity, projected traffic volumes, working challenges, and economic realities, nothing can compare with the learning that takes place once the structures are in place. Take for example Lanark Shed, on the Trans-Canada Highway just west of the western boundary of Glacier National Park. On January 1, 1963, slides overwhelmed both entrances to the shed trapping two cars and several people. While everyone was safely rescued after an eight-hour ordeal, this experience resulted in revisions to the shed design. By the following winter, tall concrete containment wings were added above both entrances (Woods, 2010).

In an incident on January 14, 1974, at Single Bench slidepath in Rogers Pass, an avalanche hit the avalanche control team (at the time called SRAWS—Snow Research and Avalanche Warning Section) in Rogers Pass just west of the existing sheds during a control shoot along the highway. Although no one was seriously hurt, the results were spectacular and ominous. A parked semi-transport truck was sent flying through the air, SRAWS and army vehicles were dislodged and damaged, and the 105-mm Howitzer used to initiate the slide was put out of commission (personal communication, Bay-Woods, 2013). Today, Single Bench Shed protects both highway travellers and avalanche control crews at this location.

Canada’s history of studying avalanche terrain and activity along transportation corridors dates from the winter of 1884-85. The Canadian Pacific Railway staffed “snow camps” in and adjacent to Rogers Pass throughout that winter to observe weather and avalanche activity. Their observations were vital to the location and design of the numerous snowsheds that would be needed to allow year-round operation of the railway across the Selkirk and Monashee mountains. In addition to numerous reports to the railway company, one of the survey engineers presented a landmark professional paper on the topic of avalanches and shed design at a meeting of the Canadian Society of Civil Engineers (Cunningham, 1887).

Similar studies of avalanche activity for the potential construction of a highway through Rogers Pass started in the early 1950s (Schaerer, 1995; Webb, 2011). In a tenacious and dedicated career spanning more than five decades as an employee of the National Research Council of Canada and as a private consultant, Peter Schaerer played a key role in locating and identifying design requirements for all nine Canadian highway snowsheds—from Sputnik to the Great Bear.

ACKNOWLEDGEMENTS

I would like to thank Jim Bay, Peter Schaerer and Walter Schleiss for sharing their first-hand experiences related to Canada’s highway snowsheds. Jeff Goodrich of Parks Canada kindly provided access to the unpublished plan showing avalanche activity at Sputnik 1 in 1958. Jacolyn Daniluck of Parks Canada and Cathy English of the Revelstoke Museum and Archives offered valued editorial suggestions on early versions of this article.

SOURCES

Cunningham, G. C. 1887. Snow slides in the Selkirk Mountains Transactions of the Canadian Society of Civil Engineers 1 Pt. 2: p. 18-31.

Schaerer, P. 1995. Avalanche studies Rogers Pass 1956 – 1961. Unpublished.*

Schleiss, V.G. 1989. Rogers Pass Snow Avalanche Atlas Glacier National Park, British Columbia, Canada. Revelstoke, BC, Canadian Parks Service, p. 313

Webb, J.R. 2011. Tales of a Highwayman. J. R. Webb, selfpublished, p. 253*

Woods, J. G. 2010. Snow War: An Illustrated History of Rogers Pass, Glacier National Park, BC.*

* available for viewing at the Revelstoke Museum and Archives

By Dave Gauthier and Dr. Bruce Jamieson

INTRODUCTION

 In 2003 Juerg Schweizer and others posed the following important questions for future research: How can field workers test for propagation propensity? Which properties of a slab and weak layer describe the fracture propagation propensity?

Photo 1: This is a size 3.0 avalanche that we triggered from a safe place 150 m away in February 2007. Propagation propensity was clearly very high here, and we didn’t need a field test to observe it!

In this article, we’re reporting on three years of work at the University of Calgary (ASARC) spent trying to answer the first question: How can we test for propagation propensity in the field? One of the main objectives of this work was to develop and verify a practical testing method, one that was intuitive, easy to do, easy to interpret, and could provide practitioners with specific information about the fracture propagation propensity of any slab-weak layer combination. Photo 1 shows a case of very high propagation propensity.

In recent years, we’ve seen some exciting advances towards addressing the propagation problem in field tests. Fracture character, shear quality, and release type observations are becoming widely used and accepted additions to the standard compression test (CT) and Rutschblock test (RB) results, and have been shown to relate to propagation propensity. At the 2006 ISSW, Ron Simenhois and Karl Birkeland presented their “extended column test” (ECT) as a new method specifically designed to investigate propagation propensity in the field. They presented an amazing dataset showing that the ECT was almost perfect in predicting skier and explosive triggered slab avalanches, and the method is already widely used by the American avalanche community.

Each of these new observations and methods use some sort of surface loading or impact (taps on a shovel or a jumping skier) to initiate weak layer fracture, which of course leads to the propagation of that fracture across the test column. Our approach to the problem was to design a test method that didn’t rely on fracture initiation by surface loading. This isn’t a criticism of the CT, RB, or ECT. In fact, we were mostly trying to find a way to separate fracture initiation and propagation in the test column, so that we could focus on the propagation part in our analysis.

We eventually settled on a method that uses an extended column design like the ECT, only oriented parallel to the fall-line, with the fracture initiated by gradually cutting into the weak layer with a regular snow saw. We’re calling it the “propagation saw test” (PST). Aside from making the analysis simpler—in that we could easily separate initiation and propagation in the test results—this method has a further advantage over the others in some cases. With no surface loading, we can test weak layers of any depth in the snowpack (i.e. Photo 2). Where the CT, RB, and ECT are limited to weak layers down 1.0-1.2 m, we have tested weak layers with up to three metre thick slabs. The limitation was only how much digging we were willing to do!

Before reading further, it’s important to remember that we’re not trying to reinvent slope scale instability assessments, or take experience and local knowledge out of avalanche forecasting and decision making. In fact, we’re not even trying to replace the CT, RB, ECT, or any other method in widespread use. We’re simply trying to provide one more tool to help practitioners answer a specific question about a specific part of the avalanche release problem: What will happen once a fracture is initiated in this weak layer? Will it propagate far and wide? What is the propagation propensity of this slab and weak layer combination?

Photo 2: The slab we tested here was over 150 cm thick, and results from testing on this flat terrain were almost perfectly reproducible on nearby slopes. The PST works with slabs of any thickness, but columns like these can take 30-45 minutes to prepare. The three metre thick ones take hours.

TEST METHOD

Terrain/Snowpack/Site Selection

Unlike almost every other instability test, the PST requires that the user choose a specific weak layer to test. Often, local knowledge, experience, or operational objectives determines the layer(s) of most interest for information about propagation propensity, especially for the deep ones. Other times, a fracture line profile, test profile or a CT or RB might identify a weak layer that warrants further investigation. As we already mentioned, there is no real limit to the slab thickness or depth of weak layer that can be tested with the PST, other than the time and effort required to excavate and prepare the test column. It can be very tricky to get a 3m tall column perfectly aligned and shaped to the correct width, and they can tip over and crush you if you aren’t careful.

In developing the PST we spent a lot of time in the field doing experiments to investigate the effects of several variables on test results. In terms of terrain and site selection, we could rarely detect the effect of slope angle on test results. Where there was some slope dependence, it was minor. This means that—spatial variability notwithstanding—we could do a test on the flats at the top of a slope, and get the same results as if we did the test right on the slope. This is an advantage in many cases where you can’t access the start zone safely, or don’t want to dig a huge pit in the middle of a run. Other than the freedom to test any slope angle, and apply the results to adjacent slopes, we recommend the same approach to site selection that you would use for other methods.

Test Columns

Figure 1 is a photo of a fully prepared test column. Like the ECT, we use an extended column design. However, in the PST the column is 30 cm wide across-slope, and 1 m long down-slope. The column must be isolated completely from the surrounding snowpack, to a depth below a weak layer of interest. Note that if the slab is thicker (vertically) than 1 m, the down-slope length of the column should be extended so that it is approximately equal to the slab thickness. A length-greater-than-height geometry is required.

We almost always used a Rutschblock cord and two probes to create the side wall and to isolate the column. It’s a good idea to highlight the weak layer with a soft paintbrush or the back of a glove. This makes it much easier to follow thin weak layers with the saw, and helps identify the softest parts of thicker layers.

Test Method

Once the column is isolated, insert a standard snow-saw completely into the weak layer at the down-slope end of the column, non-serrated edge first. Next, quickly drag the saw through the weak layer towards the upslope end of the column. At some point during the cutting, weak layer fracture will start propagating rapidly ahead of the saw. Stop cutting and keep the saw in place, and try to watch the very rapidly propagating fracture. One of three things will happen:

- the fracture will run all the way up the column to the upslope end and the slab will be completely detached; or

- the fracture will propagate a short distance and stop when the slab fractures (like a crown); or

- the fracture will propagate a short distance and seem to stop for no good reason.

The important observations for interpreting the results of the test are:

1. Did you cut more than half (> 50 cm) or less than half (< 50cm) of the test column when propagation started?

2. Did the fracture propagate the whole way across the column, or did it arrest within the column?

Our verification studies, described in the next section, showed that these two pieces of information (the amount of column that was cut and whether or not the fracture crossed the entire test column) are all you need to say something about the propagation propensity of the slab-weak layer combination.

Figure 1: Photo of a propagation test column showing the dimensions and cut direction. We usually prepare the side wall and isolate the column with a rutschblock cord and two probes. Make sure the column is completely isolated from the surrounding snowpack to a depth below the weak layer of interest.

VERIFICATION STUDIES

Method

One of the most difficult parts of this project was trying to figure out a way to “test the test.” The usual approach would be to ski-cut a slope and, based on the results, classify it as stable or unstable, and then compare the field test results with the ski-cut results. For this study, we needed to find a way to observe initiation and propagation separately, and then compare those observations to the field test results.

Of course, when a ski-cut resulted in an avalanche we could say for sure that we had fracture initiation and propagation. On the other hand, when the ski-cut didn’t result in an avalanche, we knew that a fracture hadn’t propagated, but in order to say anything about propagation propensity we needed to know whether or not we had initiated a fracture in the weak layer. If the ski-cut did fracture the weak layer, but it hadn’t propagated, we could say that there is low or no propagation propensity there. However, if there was no initiation we couldn’t say anything about propagation.

Our approach was to dig out the ski tracks in a few places whenever we had no result from a ski-cut, and take a good look at the weak layer to see if we could find evidence of fracture initiation around the skis. This way we had an objective observation of propagation propensity to compare with the test results. Photo 3 is an example of one case where we did find initiation, but not propagation.

Over the course of the 2007 field season, we made observations on 18 slopes with observed initiation and propagation, five with initiation but no propagation, and five with no initiation. Most of our results came from the 4 February 2007 weak layer, although we tested it in many locations around Blue River and Rogers Pass, where it was well-developed surface hoar, and around Kicking Horse Mountain Resort where it was a thin faceted layer.

Results

Propagation likely (if triggered): Our results showed that if less than half of the column was cut when propagation shot ahead of the saw, and the fracture propagated to the end of the isolated column without arrest, fractures—once initiated—were likely to propagate and cause a whumpf or avalanche. In our dataset this prediction was correct every time, provided the test column was the correct length.

Propagation unlikely (if triggered): If we had to cut more than half of the test column when propagation started, or if propagation arrested at slab fractures or for any other reason before reaching the end of the column, we found that weak layer fractures were unlikely to propagate once triggered. These predictions were correct 72% of the time in our dataset. This means that in 28% of cases where the test was predicting low or no propagation propensity, we were right next to skier-triggered avalanches or whumpfs. These “false stable” predictions are particularly dangerous, and it’s very important to understand where and when they might occur.

The false stable predictions in our dataset generally occurred in thinner and softer slabs than the correct predictions. In most of these cases the compression test and Rutschblock test predicted the unstable conditions correctly. Therefore, it’s very important to be cautious when interpreting the propagation saw test results in thin and soft slabs, especially soon after the weak layer is buried and the layer is just becoming active.

Comparisons

At each test site, we always did two or more compression tests and observed fracture character, usually did a Rutschblock test and observed release type, and always did a detailed profile and calculated Yellow Flags for the slab and weak layer. We then used the standard interpretation rules for predicting skier-triggering with these methods, and compared them to the predictions of the propagation saw test and our observations of initiation and propagation on the slope. We weren’t trying to determine which one is the best instability test, but we were trying to understand which one was giving the best information about the propagation part.

Our results showed that the propagation saw test was just slightly better overall, but had many more false stable predictions than the other methods. However, the standard methods had many more false unstable predictions. The standard methods often overestimate instability, because they are testing initiation and propagation, whereas the saw test captures the propagation part better. When we analyzed only the cases of observed initiation with and without propagation, the saw test performed better than the other methods, mainly because it was much better at predicting “no propagation” than the other methods. In a nutshell we found exactly what we hoped for: the propagation saw test is not a replacement for the more traditional instability tests, but it is providing some information about the propagation part of the avalanche release process that the other methods are missing.

One further advantage worth mentioning again here is that the propagation saw test works well for weak layers buried at any depth in the snowpack. The other methods are usually limited to the top 1 m or so, where they are very accurate and where human triggering is most likely. The saw test may be most useful for following a lingering layer long after burial and determining whether or not it is a still a concern, to help answer the “What will happen if I find a thin spot and trigger this layer?” question.

Photo 3: This is an example of excavated tracks from a ski cut where the skier did initiate a weak layer fracture beneath their skis, but the fracture didn’t propagate to release an avalanche. In this case the propagation propensity would be low, even though triggering was easy.

CONCLUSIONS

In summary, the Propagation Saw Test (PST) seems to be able to replicate propagation behaviour likely to be found on nearby slopes. Lots of fracture propagation in the test column, without arrest or interruption, means that propagation propensity is probably high in that snowpack. The test isn’t really providing any useful information about how easy or difficult it might be to initiate or trigger a weak layer fracture, but what might happen if it’s triggered. Remember to use caution interpreting the test results in thin or soft slabs, and that this test is only a tool to help answer a very specific question about the snowpack.

We hope that many professionals will give the PST a try this winter, and we welcome any feedback or comments from anyone. For more detailed information about this project, you can download Dave’s thesis from the ASARC Website (www.ucalgary.ca/asarc). Beware that reading it may result in severe boredom and drowsiness.

AUTHOR INFO

Dave Gauthier, Dept. of Civil Engineering, University of Calgary, davidmgauthier@gmail.com

Bruce Jamieson, Dept. of Civil Engineering, University of Calgary, bruce.jamieson@ucalgary.ca

By Curtis Pawliuk

ALLEN CREEK RIDING AREA IN LOCATION KNOWN AS OLD HILLCLMB, SHOWING TYPICAL USE. NOTE OPTIONS FOR STUDY IN MIDDLE OF PHOTO // CURTIS PAWLIUK

IS CONSISTENT AND WIDESPREAD USE of more popular managed snowmobile areas creating a growing and dangerous sense of inflated experience and over confidence in mountain terrain?

British Columbia is home to approximately 85 snowmobile areas that are classified as managed. These managed areas are operated and overseen by local organizations and clubs in partnership with Recreation Sites and Trails BC, a department of the Ministry of Forest Lands and Natural Resource Operations.

Outside pressures like the Species at Risk Act and conflicts over land use are ultimately limiting motorized (snowmobile) access to many areas of the open backcountry. As access to BC’s backcountry becomes more restricted, the snowmobiling public is more likely to utilize these managed recreational snowmobile areas.

The word managed may be a bit misleading. The typical agreement has local clubs or organizations maintaining a groomed trail that may or may not lead to an alpine shelter as its final destination. Many of these access trails are mechanically groomed and are access points to a variety of areas, including treeline and alpine terrain. These “play” areas can see very heavy use by snowmobilers of all ages and riding abilities although there is no form of management beyond the end of the access trail.

Naturally some of these areas are quite a bit busier than others and some can see hundreds of users over any given weekend. Regular winter season use of these areas can begin as early as the beginning of November and continue on well into May.

One of the areas in BC I am most experienced with is Allen Creek. This is very large area that is bound on all sides by legislated wildlife closures, leaving boundaries that are quite clear. At times, especially during periods of extended drought, fresh lines can be difficult to find. Allen Creek is likely one of the most frequented managed snowmobile areas in Western Canada. The area holds a large mix of accessible terrain with ATES classifications ranging from non-avalanche terrain, simple, challenging and complex areas. All of the managed areas around BC have been ATES mapped through multi-year projects between Avalanche Canada and Recreation Sites and Trails BC.

Allen Creek holds the same features as any high alpine mountain environment, and after a busy week it is not uncommon to see 80% of the terrain within the area’s relatively large boundaries resembling a parking lot, with every morsel of snow absolutely steam rolled. This phenomenon begins at the start of the snowy season (generally mid-November) and typically ends in late April or early May depending on the year. Compaction of the annual snowpack within the area’s boundaries is extensive. During times of infrequent snowfall little terrain is left untouched. This includes slopes of 45-50 degrees or steeper, including concavities, convexities, creek beds, gullies, and all aspects and elevations at treeline and above.

Over the last eight seasons of frequenting these areas multiple times per week and having to regularly search for that elusive unaffected location for stability tests and snow profiles, I have spent a significant amount of time thinking about the effects of compaction in these popular public snowmobiling areas. Extensive snowmobile compaction not only has relevance to stability and avalanche hazard but it also exerts an influence on the riders in the form of human factors such as familiarity and scarcity.

ALLEN CREEK, LOCATION KNOWN AS SUPERBOWL. NOTICE THE HEAVY USE IN CHALLENGING TERRAIN // CURTIS PAWLIUK

As riders become more skilled and push the technical limits of their sport, be it strictly snowmobiling or snowmobile assisted ski touring, it has become increasingly difficult to find a location within Allen Creek (and many other managed snowmobile areas) that hasn’t met a season’s worth of sled or ski traffic. When I am able to find an untouched location, I begin to wonder—is it truly representative of the overall snowpack condition within the region?

As an area representative, acting as the general manager and avalanche technician for the local snowmobile organization and operating a snowmobile backcountry guiding and avalanche education business, I try to regularly convey important local information relating to the snowpack and riding conditions within these managed areas to our users via email lists, social media and general correspondence.

I often think about the effects of compaction within these popular areas. Managed snowmobile areas throughout BC receive hundreds if not thousands of user days per weekend, and many thousands per season. This does have a profound effect on the snowpack and the avalanche hazard within these regions; it is likely a contributing factor to why we don’t see more incidents involving snowmobilers given the nature of the terrain they travel in. The majority of the snowpack within managed areas is simply compacted to such an extent that it behaves more like a modified snowpack than it does like the less-frequented backcountry.

Much of the public rides in or travels through complex terrain. On any given winter day in BC, there are nonguided, recreational snowmobilers with unknown levels of training moving through large expanses of alpine terrain. Thankfully there are minimal reported avalanches, whether simple involvements or fatal accidents.

A few key questions come to mind regarding these managed public areas, the snowmobile use they see and the compaction that results:

• Does the extensive compaction in these heavily used managed areas result in non-event feedback, which is potentially developing a growing and dangerous sense of inflated experience and over-confidence in mountain terrain?

• Should this change our messaging to riders within specific regions?

• As professionals, how do we start to understand the role of compaction in these areas?

• When do we address this growing and likely inaccurate sense of self-confidence and complacency?

• If we do not openly discuss the idea of compaction within these areas and its potential benefits and dangers, are we withholding possibly life saving information?

• Should we communicate the effects of compaction in the public bulletin?

My personal feeling to many of these questions is yes, but how?

From my experience over the last eight years of observations, the heavily used managed recreational areas are providing a safer experience, with reduced avalanche hazard due to mechanical compaction. My feeling is that we address the idea in greater fashion. We can make our public avalanche safety programs stronger by recognizing and addressing the extensive compaction that regularly occurs at managed snowmobile areas. The question looms: how is this message most effectively delivered?

Not everyone chooses to utilize managed areas. Recreational users may seek out more elusive and secluded areas where regular compaction over a very large common area is no longer the case. This decision to push beyond compacted areas may come with time and/or the individual’s progression and experience level in the activity, or simply from a desire to find fresh tracks in times of low snowfall. They could also simply be following a blind desire to go off the beaten path even though their experience level may not be there. There are many human factors that influence us all, especially newcomers to mountainous terrain.

CLEMINA CREEK GOAT RIDGE BOWL. HEAVILY USED, PLANAR SLOPE REACHING UPWARDS OF 45°. NOTE LEFT OF PHOTO, NOT AS COMPACTED AND IS A REGULAR PERFORMER CAUSING A FATAL AVALANCHE IN THE 2013/2014 SEASON // CURTIS PAWLIUK

Due to their intense use, managed areas may be best looked at and discussed as a stepping stone to gaining experience with mountain terrain—to increase personal snowpack assessment and general backcountry skills before moving into large, less compacted snowpacks which arguably present a greater hazard.

As instructors, mentors and educators, when should compaction in managed snowmobile areas come into the conversation? Currently, I have not found anything addressing the idea that popular managed recreation areas may be safer due to the compaction phenomenon. There are many points that could be argued and all need a focused attention, though I have seen the benefits of compaction within these areas for many years.

I believe our lessons and correspondence to the recreational snowmobile community need to address a stronger message on the impacts of compaction in heavily frequented areas. That message may simply be that on a high hazard day, a managed area may provide a rider with a safer experience than the untouched and raw backcountry. However, I’m left with the question of how could we effectively convey this message without causing more harm than good?

By Scott Thumlert and Bruce Jamieson, Applied Snow and Avalanche Research, University
of Calgary

AGGRESSIVE SKIER: “WHAT DO YOU THINK ABOUT CHIMO’S RUN?”

SMART SKIER: “THAT SURFACE HOAR LAYER IS PROBABLY IN THERE.”

AGGRESSIVE SKIER: “WELL, WE HAVEN’T SEEN ANY NATURAL ACTIVITY ON THAT LAYER IN A COUPLE DAYS.”

SMART SKIER: “YES, BUT IT’S PROBABLY DOWN ABOUT 100CM, SO IF WE TRIGGERED IT, IT’LL GO BIG.”

AGGRESSIVE SKIER: “DUDE, THERE’S THAT WIND CRUST IN THERE THAT WILL FOR SURE BRIDGE OUR STRESS!”

SMART SKIER: “I DON’T KNOW WHAT THAT MEANS, AND IT SOUNDS MADE UP!”

FIG. 1: MIKE WHEATER LOADING THE SNOW SURFACE ABOVE THE SENSORS. THE SENSORS ARE MOUNTED TO LONG ALUMINUM SHEETS THAT ARE INSERTED INTO THE SIDE OF THE PROFILE. THE DATA LOGGER IS IN THE BLACK BAG.

This hypothetical conversation discusses how deep our stress (force) penetrates the snowpack when we ski or snowmobile. How much does it depend on the kind of snow? How much snow of what kind do we need to effectively bridge a weak layer? When can we start to ski avalanche slopes with a weak layer in the snowpack? How can we explain sudden fractures beneath crusts in stability tests followed by no activity on that layer?

Juerg Schweizer and Bruce Jamieson (2001) investigated slab properties for many skier-triggered avalanche slopes. They found that most slabs are less than 60cm thick, rarely more than 100cm, but sometimes over 150cm. This study provided a lot of valuable insight into the skier’s impact on avalanche slopes. But there is a lot of variation in the slab depth data; how would snowmobile-triggered slopes compare and what about the properties of those slabs?

To shed more light on how skiers and sledders impact the snow, we have been placing sensors at different levels in the snowpack and recording the force transmitted by a skier or sledder (Fig. 1). Not everyone loves boxplots as much as researchers, so Fig. 2 shows some colourful pictures of the numbers for snowmobile measurements. The pictures are separated into three typical snowpack resistance profiles: soft, medium and supportive. The hardness profile is shown on the left of the graph. The plots are made for a 35° slope (which why the bulbs are shifted to the right slightly).

FIG. 2: THE PLOT SHOWS CALCULATED STRESS VALUES THAT ARE CALIBRATED TO MATCH MEASUREMENTS OF A SNOWMOBILE (σ IS THE SYMBOL FOR STRESS). THE DATA ARE GROUPED INTO THREE TYPICAL SNOW RESISTANCE PROFILES SHOWN ON THE LEFT OF EACH PLOT: PLOT A FOR SOFT, B FOR MEDIUM AND C FOR SUPPORTIVE. THE BLACK NEAR THE SURFACE OF THE PLOT REPRESENTS THE AVERAGE SNOWMOBILE PENETRATION INTO THE SNOW COVER.

FIG. 2A: SLED CONTOUR 2013 CALIBRATED SOFT SNOW.

FIG. 2B: SLED CONTOUR 2013 CALIBRATED MEDIUM SNOW.

FIG. 2C: SLED CONTOUR 2013 CALIBRATED HARD SNOW.

We see the stress bulb for the soft profile about 75cm into the snowpack (Fig. 2A), whereas the bulb for the supportive profile is about 35cm into the snowpack (Fig. 2C). The average penetration of the snowmobile is shown as black at the top of the bulb, and, as expected, the soft profile allows more penetration compared to the supportive profile. Looking at these plots, it becomes obvious that our stress bulbs start beneath our sled or skis. So, if it is over-the-head 50cm ski penetration, then the stress bulb starts at 50cm and goes deeper from there (minus some stress absorbed by deforming the powder). The idea of harder snow supporting and spreading skier and sledder stress is not new; many folks call it bridging. Most Rockies ski enthusiasts keenly evaluate bridging as the season progresses until pesky depth hoar layers are buried deeply enough.

So the question is how much snow of what type do we need to bridge a weak layer. Many experienced ski gurus have an intuitive answer that, as always, depends on many factors. In casual conversation with many ski guides, the answer to this question varies greatly. Based on the stress measurements and using skier stability indices (Föhn 1987, Jamieson 1995), we arrived at a bridging index value of 130 for skiing. The bridging index is simply the thickness of layer multiplied by the hardness (1 for Fist, 2 for 4 Finger, 3 for 1 Finger, etc). What does bridging index of 130 mean? It can represent an infinite number of hardness profiles, but here are some examples:

• 50cm fist, 40cm 4F
• 20cm P, 25cm 4F
• 10cm F, 15cm 4F, 30cm 1F

Investigating a little further, we pulled some old ASARC profile data from skier-triggered slopes and looked at the bridging index. Fig. 3 shows the frequencies of bridging index values for skier accidental and ski-cut avalanches size 2 and larger. The middle of the bridging index values is about 130, but what about all those larger values to the right of 130? Those would probably be larger avalanches as well. As a first pass, this concept shows promise but needs some more investigating—more to come.

FIG. 3: FREQUENCY OF BRIDGING INDEX VALUES FOR 50 SKIER TRIGGERED AVALANCHES (SC AND SA). ONLY AVALANCHES SIZE 2 OR LARGER ARE SHOWN.

For now, let us fast forward a little in time. Let us assume we have a good idea how much snow of what type it takes to bridge a weak layer. We are out skiing and we are pretty sure we have enough bridge above our weak layer, but we should do a quick test to make sure. We dig out a small hole, cut a 30cm x 30cm column and start tapping away. Pop! We get a sudden fracture on those facets under the crust.

Scott Davis and Bruce Jamieson chatted about this hypothetical scenario this spring in Penticton. For many good reasons, in all our snowpack tests (CT, ECT, PST, DT, ST, RB— there are a lot!), we isolate a column of some size. Cutting of the snow when isolating a column eliminates the bridging strength of the layers. Consequently, there are many situations where we get sudden results, often under a crust, but do not see avalanches on the layer. Over coffee recently, Bruce remembered a well-developed facet layer under a 20cm hard crust in the North Columbias. The layer was producing sudden fractures, but guides were skiing steep open terrain without triggering avalanches. Fig. 4 shows some stress measurements from within stability tests. In some, we isolated the normal 30cm x 30cm column; in others, we only isolated the front wall, leaving three sides intact. We see more stress in the isolated columns than the unisolated ones, which is one reason why sudden results sometimes occur in snowpack tests but the adjacent slope cannot be triggered.

FIG. 4: STRESS (σ IS THE SYMBOL FOR STRESS) AT VARIOUS DEPTHS FOR ISOLATED AND UN-ISOLATED COLUMNS. THE MEASUREMENTS ARE FROM A TEST SIMILAR TO THE COMPRESSION TEST WHERE WE TAP ON THE TOP OF THE COLUMN. THE BLACK LINE IN THE BOXES IS THE MIDDLE VALUE AND THE BOXES ARE THE HALF OF THE VALUES.

Bridging is an important concept to understand, although the usual caveat about the highly spatially variable snowpack applies. Even if we figure out how much snow is needed for effective bridging, thin spots with much less bridging always lurk. Much of the data shown here is preliminary and is presented to spark discussion and thought (i.e., do not take the 130 number as gospel!). This is currently an active research topic, so expect more information in the near future.

For further reading, read this more detailed paper submitted to ISSW in Grenoble.

REFERENCES

Föhn, P.M.B., 1987. The stability index and various triggering mechanisms. IAHS Publication, 162, 195-214.

Jamieson, B., 1995. Avalanche prediction for persistent soft slabs. Ph.D thesis, Department of Civil Engineering, University of Calgary, Alberta.

Schweizer, J. and Jamieson, B., 2001. Snow cover properties for skier triggering of avalanches. Cold Regions Science and Technology, vol 33, pp 207-221.

Thumlert, S. and Jamieson, B, Submitted. Measurements of triggering stress transmitted through the upper snow cover. Proceedings from the International Snow Science Workshop, Grenoble, France.

By Thomas Exner

At around 5:30 in the morning my girlfriend Jacqui and I drank our morning tea while gathering our tools and crampons in preparation for our last climb of the season. I was visiting her in Canada for the second time that season and had already spent a few weeks in the Banff area prior to that day. Our objective was Professor Falls. A nice classic, mellow ice route with a great reputation, it would be the first time climbing it for both of us.

Every time we ventured out in the mountains we put a considerable amount of effort into planning. Most of the time we would gather all the information available to us, such as checking out the avalanche bulletin, analysing weather maps and talking to the public safety wardens. This was the only day we didn’t do our usual homework. We were familiar with the local conditions and comfortable with our decision relying on the information we had. We didn’t know that by not calling the safety warden we were missing crucial information. That decision almost cost us our lives.

That morning we rode our bikes along the long approach until we could not take them any further. Professor Falls is located on the north side of Mt Rundle, a popular climb with close proximity to Banff. As we rode along on that chilly morning, I remember discussing the weather and the frost on the ground. This was a good sign for that early March morning. We expected to finish the climb before noon when temperatures were going to get too high. Winter was starting to feel a little warmer by that time and signs of overnight freezing were encouraging to us. We wanted to climb the route a few days earlier, but a snowfall forced us to postpone our plans. It was now about four days since this last snowfall and we were the first party to start the climb that day.

Walking up the last metres to the climb we saw the first pitches in really impressive conditions. We were totally excited about the climb and the opportunity to spend our last day in the Rockies on such a nice piece of ice. Viewing the surrounding terrain from this point of view there is no obvious avalanche danger, although we knew the potentially dangerous slopes were way above. It looks more like a wonderful climb in impressive surroundings with minimum objective dangers. Everything seemed to be perfect.

Professor’s is popular for a good reason. The approach leads along the Bow River, offering impressive views of the huge north face of Mt. Rundle and an area known as Trophy Wall, where some of Canada’s hardest and most famous ice climbs can be found. Professor’s itself consists of several steps of steep and fat ice, separated by flat bands and gullies. The first pitch, just a short walk off the Bow Valley trail, offers moderately steep and excellent ice squeezed in between two rock faces. The flat bands on top of each step provide comfortable belaying and offer good views above the Bow Valley.

When we started the climb we were just ahead of another party. It took us a while to get going on the the first pitch, but after warming up and getting a feeling for the ice everything ran smooth and we enjoyed the excellent ice pitch after pitch. At one point, somewhere near the middle of the climb, we met a solo climber heading down who seemed to appear out of nowhere. As Jacqui arrived at the anchors after seconding the pitch before the last crux pitch, she continued ahead on the final horizontal ice section. Walking a rope length ahead of me, she and I moved together as we approached the final pitch. My eyes were focused on the crux pitch, anticipating these last metres of perfect ice. I was coiling up a few slings of the rope since I was walking a bit faster than Jacqui. Time-wise, we were doing pretty well since it was still well before noon. We were about to finish the climb soon, rappel down, and still have enough time to enjoy the afternoon.

Suddenly I heard a bang above me, forcing me to look way up over the huge rocky cliff several hundred metres above us. What I saw was shocking – a huge powder cloud. At first I thought it was too far to the right to reach us and tried to relax. Keeping my eyes on the cloud for a couple of seconds, I realized I was wrong. It was growing incredibly fast and I knew for sure – a huge avalanche will come right down over us.

I yelled to Jacqui who hadn’t yet noticed anything. “Avalanche, go to the right!” She turned around to me with a frightened expression on her face. She couldn’t see what was going on from her perspective and yelled with a fearful voice, “What should I do?” I told her again to go to the right and hold on.

Since the powder cloud was coming from the right, I hoped the little rocky cliff on the right hand side of the gully would provide shelter. I was positioned near the edge of the gully and jumped to the right under some slightly overhanging rock, getting out of sight from Jacqui and possibly seeing her for the last time. I tried to get into a comfortable position while trying to build some air space with my hands and arms in front of my head. Then I noticed a small tree just to the left of me. I ran around it once, wrapping the rope around its trunk. This would be the our only anchor.

I was sitting back pressed against the cliff and waiting – for the end? I remained surprisingly calm. I don’t know why, because we would probably die. I can’t tell how much time passed since I heard the bang. Maybe it was 10 seconds or maybe 30, I don’t know. It seemed like an eternity. We did have enough time to communicate, position ourselves, run around a tree, reposition, and even wait.

At that moment I expected a huge shock wave which would probably kill us before the solid snow hit. I could see the enormous powder cloud quickly approaching the gully, gaining size and strength as it got closer. It was getting dark all around, stormy and loud like a huge snow storm with extreme winds. There was a heavy rumbling sound. I couldn’t see what was going on.

There was no shock wave, we are lucky. But most likely the flowing snow would cover us with metres of debris. Then it became silent and light again. I couldn’t feel any snow burying me, I was just covered with a thick layer of blown snow. I looked back down the gully. There was still snow flowing down into the main gully, totally blocking it. Most of the snow was funneled around us and managed to pile in the gullies behind us.

There must have been more than six metres of snow piled up just a few metres behind me. I waited a few more seconds until nothing was moving. I stepped forward, yelling for Jacqui. She was last located closer to the middle of the gully and I was scared, knowing her position and the massive amount of snow that just used our climbing route as a funnel. Then I heard her voice. She was a bit freaked out but fine, thank God. She told me later she had bruises on her knees and legs from clinging so hard to that little rock cliff.

We thought of leaving the gully to the side as quick as possible, fearing more avalanches to come. But there was still the other party below us and the solo climber. All three people would be not too far below us and we were suddenly overwhelmed with additional fears that they didn’t make it. We turned our transceivers to search and went down the gully as quickly as possible. Jacqui used her cell phone to contact the Park Wardens, informing them about the avalanche and the possibility of three climbers caught.

The gully was totally changed. The middle part, where we were walking just minutes before, was deeply filled with avalanche debris. The smaller steps we had climbed were practically gone and one shorter pitch had totally vanished in the debris. We were able to slide down much of the gully before we came to some anchors to rappel the rest of the climb. Surprisingly, we saw the other party doing well and on their way up to look for us. They had kept a steady pace behind us for most of the climb, but luckily managed to lose some speed and just missed the many tons of heavy snow that might have killed them. The solo climber had passed them on his way down and was well out of danger.

We called the wardens again to report no one was caught but the helicopter was already on the way – almost Euro style. Later, the warden told us they were planning to sling us out since there was still snow in the start zone. The fracture line was about 150 m wide and averaged a half-metre in depth. The avalanche fell about 700-800 m, then hit flatter terrain where it probably lost much of its energy before it reached us. The debris piled up everywhere around us except the side of the gully where Jacqui and I were hiding. It was incredible, and eerie, to look around and see the snow piled in every direction except for the two places where we stood.

We decided to rappel down together with the other party and finish this adventure quickly. At the top of the final pitch we met an American party on the way up, regardless of the powder cloud that had even reached the base of the climb where they had been standing. We really had to convince them not to continue, despite the obvious clues of avalanche danger. It was already noon at this point and so warm that it was slightly raining.

On our way back to the car we could see the top of Mt. Rundle covered in clouds with strong winds. We observed a small slide on the steep cliff to the right of the climb. As we got back to Banff the skies were clearing a bit and the sun came out. It was really nice and warm just like nothing happened. In the safe shelter of a pub we reflected upon the past few hours and a mix of emotions came up in me. I was just too calm up there in the gully. I slowly started to realize what happened to us that morning and what a huge gift it was that we were still alive. All our guardian angels had a pretty busy day.

So what went wrong that day? Is it just a freak thing that happens, an acceptable part of being in the mountains? “Yes’’ would be a really discouraging answer. It would be difficult for me to avoid all climbs with possible avalanche risk above. This cannot be the answer. We tried to figure out what went wrong in our decision-making process that day.

We postponed the climb due to a snowfall with significant winds. On the evening before our last day in Banff we discussed the situation again. The daytime temperatures had been relatively mild but still below freezing overnight in the alpine, promoting a settling of the storm snow. Everything that hadn’t avalanched already should not be triggered naturally. The hazard was rated considerable, focusing on sun-exposed slopes that might become dangerous due to daytime warming. We didn’t expect any natural activity on north-facing slopes. To be on the safe side, we decided to start at the break of day to get off the climb before noon. Based on this information we decided it was safe to go for this climb.

We didn’t know about the warmer temperatures at higher elevations, which might have been one reason for the release of such a big natural avalanche. The little storm just around Mt. Rundle put more drifting snow on the slopes above the climb, enough to trigger it. This new wind loading and the temperature inversion were hard to foresee, neither of which were forecasted. But the crucial information we missed was that natural avalanches occurred on all aspects the day before we went on the climb. This knowledge would have been a clear indicator not to climb Professor Falls that day and was easily available by a simple check with the Wardens. It was our mistake to not utilize all the information available to us.

The other factor in our mistake is less obvious. It was our last day in the area and we wanted to spend it on a nice, popular climb that neither of us had done. Looking back, I am pretty convinced that subconsciously this influenced our decision. We possibly would have made a different decision if there wasn’t the subtle pressure to end our season with a classic climb of the Rockies.

In avalanche country, most of the time you have no way of knowing if your judgement matches the real conditions. You never know how close you are because most of the time there is no feedback. It’s the feedback, though, that can sometimes be fatal. Going too long without any feedback might suggest that you always make the right decision. Looking back on the lesson from the Professor,

I am happy that I experienced it. It brought me back to the ground. I might have been out in the mountains too long without any feedback. I am sure it could have been avoided and it wasn’t just Mother Nature playing tricks on us. There were mistakes in our decision making progress. This sounds promising to me, because it can be improved. Jacqui asked me once how I know whether it’s safe or not. I told her you never really know. It’s sometimes just a gut feeling. She was not amused by my non-scientific answer and responded with, “Great. Thanks,” and kept skiing.

The night before the climb that was so close to being our last, she suffered from great discomfort while sleeping and woke up with a troubled and unsettled feeling. At least we both know now what I was trying to say.

Ryan Vrooman, Brendan Martland, Ken Black

BRUCEJACK MINE SITE

OBJECTIVES

In the spring of 2017, the Brucejack project made the decision to fully move all of its avalanche risk management over to a single platform: InfoEx. Our experience with InfoEx at other industrial and highways operations, as well as in the guiding and resort industries, led us to postulate that with some adaptation, all of our pre-existing specialized risk management tools could be ported into the InfoEx.

With the support of the CAA and some repurposing of existing modules, we were able to greatly streamline our risk assessment process. Given the diverse backgrounds of our technicians, and planned upgrades to further enhance the usability and capabilities of the platform, we envision other industry groups will see expanded possibilities for their operational risk management programs.

PROJECT OUTLINE

The Brucejack project is a gold mine and mineral exploration project on 122,133ha of land, 65km north of Stewart, BC. It lies in the Boundary range of the Coast Mountains and receives an average annual snowfall in excess of 10m. In exceptional years, snowfall can exceed 20m.

The project has four camps and almost 80km of road, intersected by multiple sections of avalanche hazard, ranging from cutbanks producing up to size 2 avalanches to runouts of size 4.5 overlapping paths. The mine site and main camp sit in the alpine at 1400m and have a combination of micro avalanche terrain features and several large paths capable of producing size 3.5 avalanches.

Currently the winter program employs a supervisor, a lead hand, two senior technicians and 14 avalanche technicians maintaining a 24 hour/day winter mitigation program. There are two camps that have separate avalanche zones to forecast and mitigate: an alpine camp at the head of a glacier and a treeline/below treeline camp.

Primary management tools include:

• Extensive helicopter, case, and hand charge explosive control program

• 6 RACS Gazex exploders

• A snow cat-based Avalauncher (rarely used)

• Manual (ski, shovel) and machine (excavator, loader, snow cat) hazard reduction

PREVIOUS FORECASTING TOOLS

During the exploration stages of the project, several Excel-based documents were created to encapsulate our forecasting workflow. These included a stability assessment, an assessment rating for each avalanche path, and an extensive Dropbox-based filing system for record keeping. We maintained both PDF and hard copies of our records. The InfoEx platform was used primarily as an information exchange.

TRANSITION TO INFOEX

During the winter of 2016-17, the build phase of the project necessitated a large expansion in the avalanche hazard management program. This ramp-up in operations was accompanied by an increase in required paperwork and filing, with some redundant record keeping practices. To streamline process, the decision was made to attempt to transition to a single platform for all of our avalanche hazard communication and risk management.

The InfoEx platform expansion and evaluating capabilities gave us confidence that it could capture our many needs. Having the modularization and customization functions available, complete data storage and near universal buy-in from the industry made InfoEx our obvious choice.

There were some growing pains associated with individual path assessments, full document transfer and the nature of our 24 hours/day program, but we were able to fully transition our hazard assessments over to the platform.

ADAPTATIONS AND NOVEL USES WITHIN INFOEX

Run list

We were able to repurpose the run list module into an individual path assessment tool. This involved changing the Run list Status Configuration to match our customized icons, colors and our site-specific hazard scale.

Much like a mechanized skiing operation, we divided our paths into geographic zones and separated them into individual tabs. The avalanche paths were then given an individual hazard rating correlating to our in-house hazard scale (adapted and modified from BC MOTI). These path assessments were prefilled from the previous day, allowing for continuity from the previous shift and capturing trend.

The comments section of the individual paths within the zone is used to track last control date and results, natural activity, and path specific comments. A report with the last 7 days of path history was seeded into the workflow as a preceding step. This allowed for a snapshot of the history and trends for each individual path.

SCREENSHOT OF PATH HISTORY IN INFOEX.

A second run list was built with tabs for the various micro terrain features around the mine site and upper camp, avalanche control roads, and the status of the defensive catchment berms. This was again defaulted to prefill from the previous day. The comments section is used to convey hazards, status of the terrain feature and/or instructions for maintenance crews. InfoEx allows us to directly email this portion of the run list to the Surface Operations department for consideration in their planning and for easy reference to avoid any miscommunication.

There are some planned additions to the functionality and customizations of the run list module that will allow for multiple columns with various prefill and heading options, an expandable comments box and the ability for multiple email lists to be attached to different run lists.

Having multiple columns will allow us to capture trend and to mark individual paths for control or as areas of concern without losing the assigned hazard rating.

Avalanche Control Module

The purchase of the Avalanche Control module allowed us to greatly reduce our paper records, improve internal communication and modernize our operation. It also acts as an easy reference for explosives deployment records. However, for forecasting infrequent paths we’re still working towards the ideal solution. Many of our technicians are accustomed to keeping shot sheets on the wall, but during storm events this could mean printing and posting as many as 30 updated sheets during a shift, which has obvious drawbacks. The current solution to this is seeding an avalanche control history into the workflow, but it doesn’t quite have the same impact as shot sheets on the wall.

The photo overlay tool allows for a historical review of control work in a specific path, but it currently lacks the capacity to review an entire zone without creating duplicate records. It is expected that changes can be made to allow recording results into a single large zone photo and also looks promising that this extension will soon include the ability to have results displayed alongside the photos. This would allow for a quick overview at the zonal/bowl/mountain scale and storing individual results at the path level.

MOVING FORWARD

With the hiring of a second developer by the Canadian Avalanche Association (CAA), several planned upgrades are in the works for this summer. Highways and industrial users have engaged strongly with CAA InfoEx staff to propose enhancements and these have augmented feedback from guiding operations and ski hills. Fortunately, there are often synergies between the suggestions from the different sectors so there should be mutual benefit when these enhancements come online.

Photo overlay

Fully replacing manual shot sheets will require more accessibility and integration with the observations and avalanche control modules. Fortunately this is in the works. Planned upgrades include the ability to pick standard colors (size 1 = green, Size 2 = yellow, etc.), the ability to set one zonal overview photo for the control route, integration with avalanche observations, and control results/observations displayed alongside.

Columns in the Run List

Adding a second column in the run list will allow us to capture trend and a third column will be used for marking a path for possible control. With the planned full customization and creation of numerous prefill options, various operations (in different sectors) will be able to customize these columns to meet their specific needs.

Email list

Having multiple email lists will allow each separate run list to be emailed to the relevant and affected users. Outputting specific run lists/path assessments/hazard assessments to targeted groups seems to have increased uptake and absorption of those summaries.

Path History listing

The ability to organize the customized report geographically as well as alphabetically will streamline the workflow process further.

Comments box

Comment boxes that automatically expand or can be expanded to a desired size will prevent scrolling for large comments in the run list module.

Time Profile

Building up this function into a modern, functional wall profile replacement will take some time. There is a strong industry desire to move to a modern digital platform but the functionality and visibility of a large wall-based time profile has yet to be surpassed in our opinion. Current plans include a linear interface, full customization of values, and the ability to display it independent of InfoEx (such as a PDF to a large wall monitor). This will be a huge leap forward in functionality and will further streamline the daily record keeping process. Weekly, monthly and end of season reports would also be just a few clicks away with accurate, customized, up-to-date and well graphed data.

THE BIG PICTURE

Since we moved our entire hazard management workflow over to InfoEx there have been significant efficiencies gained. We estimate a time savings of greater than 30 min per shift and an overall clearer picture of hazard. As an experiment it has been an overwhelming success. This platform – and specifically the run list module with its communications functionality and customization – holds great promise as a management tool far beyond just avalanche hazard for industrial and highways use. We see ski hills benefiting greatly from the streamlined record keeping and hazard communication between various affected departments, and other sectors can customize these extensions to meet their needs, such as heliskiing outfits sending emails of their run lists to various users.

Working closely with Stuart Smith, Luke Norman and the CAA team has been a very productive and positive process. As a busy 24-hour forecasting and control program with two separate offices and 18 staff, we have been putting InfoEx to the test all winter long. Our hope is that our many requests and feedback from extensive trial and error will help make InfoEx even more user-friendly and customizable for existing and future users of the product.

By Cam Campbell and Matt Macdonald

ABSTRACT

Of the 29 avalanche fatalities during the avalanche season of 2002-03 in western Canada, at least 14 were attributed to persistent deep slab avalanches, including one seven-fatality incident. The next highest number of avalanche fatalities this decade in western Canada was during the avalanche season of 2008-09 with at least 17 of the 25 fatalities attributed to persistent deep slab avalanches. Analysis of the commonalities between these two avalanche seasons showed that rain on a shallow early season snowpack, followed by a long period of clear and cold weather, set the stage for a deep slab avalanche problem. Similar early season weather occurred during the avalanche seasons of 2001-02 and 2009-10, yet a widespread persistent weak layer did not develop.

This paper presents a retrospective of the past ten avalanche seasons in western Canada. Weather, snowpack, and avalanche occurrence data are used to test the hypothesis that given weather conditions favourable for early season hard crusts with associated facets, persistent deep slab avalanche characteristics depend strongly on early season snowpack depths. It was found that below average early season snowpack depths is one of the major factors contributing to widespread persistent deep slab avalanche characteristics. Furthermore, below average and variable seasonal snowpack depths, weak, re-loaded bed surfaces, and favourable snowpack stratification for step-down fractures seemed to contribute to the persistence. By identifying early season patterns leading to the development of widespread persistent deep slab avalanche characteristics, this paper will aid in forecasting such avalanche seasons by providing a recipe using early season ingredients.

Figure 1: Image of western Canada showing the South Coast, Columbia, and Rocky Mtns. Blowdown Mid and Mt Fidelity weather stations are also shown

1. WESTERN CANADA AVALANCHE WINTER REGIMES

According to Haegeli (2004), the maritime avalanche winter regime in the South Coast Mtns (Figure 1) is characterized by a low number of persistent weak layers. Basal facet layers are not uncommon in the interior ranges of the South Coast Mtns, especially in shallow windswept areas. Although, relatively warm temperatures associated with mild air from the Pacific Ocean tends to prevent them from persisting.

The transitional Columbia Mtn (Figure 1) regime typically involves one or two facet-crust combination weaknesses, generally near the base of the snowpack, and several surface hoar layers every season.

In the continental Rocky Mtns (Figure 1) basal weak layers and deep slab avalanche characteristics are common. Therefore, this study considers persistent deep slab avalanche characteristics to be widespread throughout western Canada if a basal weak layer remains active throughout the avalanche season in the South Coast Mtns.

2. AVERAGE EARLY SEASON SNOWPACK DEPTHS

The average early season snowpack depths were compiled using a selection of tree-line and alpine weather stations in the Coast and Columbia Mtns. Data from the closest date between November 30th & December 3rd were used as an approximate of early season snowpack depth. The available values were taken from the 12 am observation on the day with the most data for each year. For the South Coast Mtns, the average snowpack depths were obtained using the British Columbia Ministry of Transportation and Infrastructure’s (MoTI) Blowdown Mid (Figure 1) and Little Bear automatic weather stations (RWIS), Whistler Mountain’s Pig Alley weather plot, and the Solar, Catskinner, and Horstman Hut automatic weather stations on Blackcomb Mountain. For the Columbia Mtns, Parks Canada’s Roger’s Pass and Mt Fidelity (Figure 1) weather plots, the MoTI Kootenay Pass RWIS, and Mike Wiegele Helicopter Skiing’s Mt. St. Anne weather plot were used.

3. EARLY SEASON ARCTIC OUTBREAKS

Table 1: Early season arctic outbreaks (AO) in western Canada.

Arctic outbreaks occur when dry frigid air that has been deepening north of the Arctic Circle spills south into lower latitudes. The blast of cold air causes temperatures to plummet and the lack of humidity creates clear skies. In western Canada, these cold clear conditions are brought on by ridges of high pressure over the Yukon or northern BC. Arctic outbreaks typically last multiple days and some can persist up to several weeks.

To identify past early season arctic outbreaks, daily minimum and maximum air temperatures as well as snowpack depths were plotted from November 1 to December 31 for each of the past ten years. Blowdown Mid, a treeline automated weather station from the MoTI RWIS network located at 1890 m near Pemberton, British Columbia (Figure 1), was deemed an ideal location representative of both the maritime and transitional avalanche winter regimes. Arctic outbreaks were identified by prolonged periods of well below normal temperatures with little to no precipitation. Corresponding surface analyses from the Pacific Storm Prediction Center were verified to confirm the presence of an arctic ridge of high pressure.

4. WEATHER, SNOWPACK AND AVALANCHE RETROSPECTIVES

Figure 2: Average early season snowpack depths in the South Coast and Columbia Mtns for the past ten years. The ten-year average for the South Coast Mtns is 98 cm, and 107 cm for the Columbia Mtns.

4.1 2000-01

The South Coast Mtns (90 cm) had a slightly below average early season snowpack depth, while the Columbia Mtns (75 cm) were well below average (Figure 1). A six-day arctic outbreak occurred mid-December (Table 1).

Data from the Canadian Avalanche Association’s (CAA) daily avalanche industry information exchange (InfoEx) suggest that a basal facet and depth hoar weak layer formed in the South Coast Mtns. Associated avalanche activity persisted until mid-to-late January, when warm temperatures, rain, and weak temperature gradients resulted in bridging, rounding, and sintering of the basal snowpack.

4.2 2001-02

The South Coast Mtns (131 cm) had a well above average early season snowpack depth, while the Columbia Mtns (109 cm) were about average (Figure 1). An eight-day arctic outbreak occurred late-December (Table 1).

According to the CAA InfoEx, a significant mid-November rain event followed by a period of below average air temperatures resulted in a facet-crust weak layer that persisted throughout the season across much of western Canada. The pattern of the avalanche activity shows the weak layer to be most persistent in the Rocky Mtns, and limited to the central ranges of the Columbia Mtns. Related avalanche activity was largely absent in the South Coast Mtns (Haegeli, 2004).

4.3 2002-03

Both the South Coast (34 cm) and Columbia Mtns (55 cm) had a well below average early season snowpack depth (Figure 1). Multiple rain on snow events occurred before a late-November seven-day arctic outbreak (Table 1), which was followed by continued clear, dry, and calm weather in early-December (Figure 3).

Data from the CAA InfoEx suggest that the early season rain events followed by clear and cold weather resulted in a combination of several persistent weak layers at the base of the snowpack that was widespread across western Canada. Associated avalanches remained active throughout the avalanche season. Additional persistent weak layers distributed throughout the snowpack created a stratigraphy prone to step-down avalanches (Figure 4). Weak reloaded bed surfaces, as well as below average seasonal snowpack depths, also contributed to the persistence. The propensity for remotely triggered avalanches made this deep instability especially dangerous.

Figure 3: Daily time series of early season 2002-03 total snowpack depth (HS), and minimum (T min) and maximum (T max) air temperature for Blowdown Mid automatic weather station located at 1890 m in the South Coast Mtns near Pemberton.

Figure 4: Snow profile from a treeline study plot on Mt Fidelity in the Columbia Mtns observed on 02 March 2003. (Profile: University of Calgary - Applied Snow and Avalanche Research).

4.4 2003-04

Both the South Coast (108 cm) and Columbia Mtns (119 cm) had slightly above average early season snowpack depths (Figure 1). A relatively short arctic outbreak occurred near the end of November (Table 1).

According to the CAA InfoEx, no basal facets formed in the South Coast Mtns. Some areas in the Columbia Mtns reported basal facets at higher elevations, but associated avalanche activity was sporadic throughout the season.

4.5 2004-05

Both the South Coast (90 cm) and Columbia Mtns (102 cm) had near average early season snowpack depths (Figure 1). A short cold period occurred at the end of November (Table 1).

Data from the CAA InfoEx suggest no basal facets formed in the South Coast Mtns. Some areas in the Columbia Mtns reported basal crusts with associated facets and mixed forms at higher elevations, but associated avalanche activity was limited to early season direct action events.

4.6 2005-06

Both the South Coast (74 cm) and Columbia Mtns (92 cm) had below average early season snowpack depths (Figure 1). An eight-day arctic outbreak occurred during the end of November and into beginning of December (Table 1).

According to the CAA InfoEx, no basal facets formed in the South Coast. Basal crusts with associated facets were observed in the Columbia Mtns, but quickly gained strength.

4.7 2006-07

Both the South Coast (146 cm) and Columbia Mtns (140 cm) had well above average early season snowpack depths (Figure 1). A deep eight-day arctic outbreak occurred at the end of November (Table 1). Data from the CAA InfoEx suggest, both the South Coast and Columbia Mtns had a well-settled and strong early season snowpack with various thick crusts that formed in October and November.

4.8 2007-08

The South Coast Mtns (82 cm) had a below average early season snowpack depth, while the Columbia Mtns (120 cm) were above average (Figure 1). A short cold period occurred near the end of November (Table 1).

According to the CAA InfoEx, basal crusts and mixed forms produced early season avalanches in the South Coast Mtns, but quickly strengthened. However, associated surface hoar at lower elevations in the Columbia Mtns contributed to increased avalanche activity, and stronger temperature gradients allowed associated avalanche activity to persist until late-December.

4.9 2008-09

The South Coast Mtns (46 cm) had a well below average early season snowpack depth, while the Columbia Mtns (102 cm) were about average (Figure 1). A mid-December eight-day cold and dry period (Figure 5) was the best example of a true arctic outbreak in the past ten years (Table 1).

Data from the CAA InfoEx suggest that the snowpack was fundamentally structurally weak throughout western Canada. This was primarily due to a widespread basal facet-crust weak layer with weak reloaded bed-surfaces contributing to the persistence. The characteristics of the associated persistent deep slab avalanche activity were most atypical for the South Coast Mtns, and more typical of a continental avalanche winter regime.

After investigating two separate avalanche fatalities on consecutive days near Whistler, Avalanche Consultant, Chris Stethem concluded that “We are dealing with a continental snowpack more common in the Rockies. This deep seated instability hasn’t been seen to this degree in the South Coast region since the late 70s” (Whistler-Blackcomb press release, 2009). Mountain conditions reports (MCR) from experienced South Coast ski guides included statements such as: “Extremely unusual conditions….. Our guiding team has not seen such dangerous conditions in this area before….” (David Lussier, Association of Canadian Mountain Guides MCR, 31 Dec 2008).

Figure 5 – Daily time series of early season 2008-09 total snowpack depth (HS), and minimum (T min) and maximum (T max) air temperature for Blowdown Mid automatic weather station located at 1890 m in the South Coast Mtns near Pemberton.

4.10 2009-10

Early season snowpack depths in both the South Coast (176 cm) and Columbia Mtns (154 cm) were well above average. A late-November rain-on-snow event was followed by a long twelve-day arctic outbreak in early December (Table 1).

According to the CAA InfoEx, the both South Coast and the Columbia Mtns had an early season facet-crust weak layer that resulted in a large mid-December avalanche cycle, but associated avalanche activity didn’t persist.

5. DISCUSSION AND CONCLUSIONS

Based on the results presented in this paper, a reasonable recipe for widespread persistent deep slab avalanche characteristics in western Canada starts with below average early season snowpack depths. It is hypothesized that a sufficiently shallow early season snowpack is required to maintain a temperature gradient favouring faceting. However, the early season snowpack must also be sufficiently deep to overcome ground cover and create a uniform bed surface.

Patterns associated with widespread persistent deep slab avalanche characteristics include hard crusts on or near the snow surface, before a prolonged period of clear and cold weather. The duration and magnitude of this weather pattern must be sufficient for advanced faceting, given the snowpack depth. Surface hoar formation during this period can increase the sensitivity to triggers and persistence of the subsequent basal weakness.

Below average and variable seasonal snowpack depths, weak re-loaded bed surfaces, and favourable mid- and upper-snowpack stratification for step-down fractures can contribute to the persistence of deep slab avalanche characteristics.

Further studies could analyze more data using statistical methods to determine significance of the contributing factors identified in this paper.

6. REFERENCES

Haegeli, P. (2004). Scale analysis of avalanche activity on persistent snowpack weaknesses with respect to large-scale backcountry avalanche forecasting. PhD Thesis, University of British Columbia. 254pp.

7. ACKNOWLEDGEMENTS

For use of their data, the authors would like to thank CAA InfoEx subscribers, Parks Canada, the University of Calgary Applied Snow and Avalanche Research (ASARC), and the BC Ministry of Transportation and Infrastructure.

By Bree Stefanson

AVALANCHE CONTROL ON EAST STROHN PEAK. PHOTO: MOTI

I MOVED TO STEWART SEVERAL YEARS AGO to work in the BC Ministry of Transportation and Infrastructure Bear Pass Avalanche Program. The afternoon before my first day of work was my first time driving Highway 37A. My jaw dropped and my neck strained as my eyes tried to take in the complexity of the avalanche paths surrounding my truck. Within the first few hours on the job, I was in a helicopter finding out where my targets were and when to deploy the charges. Each of the sixty 25kg bags that went out of the door created avalanches, including numerous showy size 3s and a handful of movie-quality size 4s. It was like nothing I had ever seen. The large paths have a vertical fall of over 2,000m and avalanches can travel upwards of four kilometres before the mass crosses the highway. The mid-sized paths were a couple hundred metres higher than the vertical fall of Castle Mountain Resort, where I had worked as a ski patroller. The smaller paths can bury a vehicle or push one into a lake.

The pass taught me a lot my first season. For example, the center of an approaching low-pressure system can slip a little south and surprise you by sneaking in the backdoor with outflow winds. Amazingly, the large avalanche paths can retain what seems to be an infinite amount of load and are capable of producing size 5 avalanches. An impressive display of nature, the large avalanches command respect for the potential damage they can produce. It was hard not to get caught up in focusing on the large paths, but the “small” paths can still put a size 3 on the road. Also, the importance of clear, timely communication to the public became paramount when living in a community that becomes isolated once the road closes.

Coming into my second season I had a better idea of what to look for and what to expect. I also knew that I had just experienced an “average” season and hadn’t seen anything “above average.” I had come to appreciate the forecasting process which was well-established within the program. This process assesses the overall avalanche hazard for an unmodified snowpack and then applies that assessment to each individual path throughout the forecast area, taking significant occurrences into account. The paths are then individually ranked on the Ministry’s five level hazard scale to identify the paths of concern and dictate specific operational procedures that the maintenance contractor is required to follow while working within the avalanche area.

FRACTURE PROFILE ON ORE MOUNTAIN. PHOTO: MOTI

The 2014-15 season started warm and wet with average amounts of precipitation, but freezing levels were often above 1,000m. In the alpine, a significant instability was buried in the fall, and by Christmas a hard slab had developed over top. When we issued a Future Planned Event notifying our stakeholders that the highway would be closed for avalanche control, you can only imagine the feedback we got from surprised locals, as there wasn’t a flake to be found in town. The control mission was successful, with avalanches to size 4 crawling over nearly bare ground and terminating within 200m of the highway. This mission greatly reduced mass from our alpine start zones, and even though we had large deposits visible from the road, no one in town was buying my story.

The first time I heard the term “atmospheric river,” a significant storm that was forecast to track well to the south had shifted its course and was headed towards Stewart. The millimetres were stacking up on the XTs and we were all trying to forecast the effects of 100mm in a 30-hour period on our snowpack. We compared the various forecast models, attempting to pinpoint the peak of the storm. We applied the forecast to our current snowpack and attempted to hypothesize the timing and character of the expected avalanche cycles. Our theory was that there would be too much rapid loading for the paths to retain significant mass, and the paths would shed during peak loading. We anticipated the freezing levels to rise and induce a secondary wet cycle as the snowpack became saturated. With saturated runout zones, deposits from large avalanches initiating later in the storm would slow down, ideally stopping above the road. We planned a control mission for the peak of the storm, targeting rain-saturated paths below treeline. This closure would also empty the road of travelling public, allowing us to get a handle on the avalanche character and where the deposits were actually stopping without added pressure.

The storm was intense, starting with 3-5mm H2OE per hour, steady for hours. Twelve hours into the storm, snow levels were above 1,100m and precipitation rates had reached up to 7.4mm an hour. I was relieved once the road was closed for control, as the large paths were retaining their mass.

AN AVALANCHE DUSTS BEAR PASS. PHOTO: MOTI

Fortunately, the ceiling was high enough to access the below treeline start zones and the snowpack was saturated enough to release wet loose and slab avalanches. After a three hour mission, our BTL concerns were mitigated and we had plenty of daylight to fly through the pass to observe the natural occurrences. Sure enough, as we flew by, we saw every large alpine and mid-elevation path had healthy deposits below them, with all deposits stopping above the highway. We ran through our path hazard avalanche risk table and all of our paths of concern had released, with any residual hazard still falling well within our operational risk band. We made the call to open the road and continued to monitor avalanche activity.

The storm ended as fast as it came. When it was all said and done, Stewart had received 146mm over a couple of days with 110mm falling within a 24-hour period. This exceeded by twice as much the previously recorded maximum precipitation amount for a 24-hour period in Stewart in March.

At first light I drove through the pass with the clear morning sky showing crowns throughout the pass. By 10:00 a.m., the wind increased, grabbing all the new snow available for transport and quickly erasing the crowns.

Fortunately, the weather continued to improve and conditions were favourable for control the following day. We spent most of our mission above the treeline, producing numerous size 3 to 3.5 avalanches and a few size 4s. The deposits of these reloaded paths easily traveled over the debris piles produced during the storm, with some just stopping shy of the road. The avalanches were stunning. They were dry and moving fast until they hit the saturated snow, where they’d push a slow moving finger of wet mass through the run-out zone. It was impressive to see the power of the air blasts from the two plunging avalanches that dusted the road.

A PANORAMA OF THE FRACTURE LINE ON ORE MOUNTAIN. PHOTO: MOTI

Following the mission, I drove through the pass to capture the toe distance mass of the deposits, and I reflected on the storm, the natural cycles and the control missions. I thought about the various avalanche path characteristics over the elevation bands and the many avalanche problems I had just seen. In one storm there was storm slab, persistent slab on surface hoar, large plunging, loose dry, loose wet, and wet slab, as well as the potential for large avalanches to detach huge fins of glacial ice amplifying the deposit size. I was glad that we had eliminated the deep slab problem formed earlier in the season as it had become active in slopes adjacent to the forecast area, and this would have increased the magnitude of the impacts to the highway during the storm.

The Bear Pass is a wild place to work during a significant storm event, and the area provides a fabulous opportunity to learn a lot about avalanches. I am grateful to have seen an event like this and to have had such a solid team to work with through the season. I’m now in my third season in the pass and from the deposits I’ve seen in the archived photos, all I really know is that I have a whole lot more to learn.

By Greg Johnson and Karl Klassen

PHOTO: CHRIS CHRISTIE

The new Avaluator will soon be on the market. The prototypes for this tool show great promise as an effective solution to a complex problem, and have garnered critical acclaim from risk specialists. However, to apply the trip-planner effectively, the user depends on two important factors: an avalanche danger rating and an avalanche terrain exposure scale (ATES) rating. The first is a well-established system, and a current danger rating can be found for most places in western Canada frequented by winter backcountry users. The ATES system, developed by Grant Statham and Bruce McMahon of Parks Canada, is newer and to date has been implemented almost exclusively within the National Mountain Parks.

The ATES is a three-level scale that rates terrain as simple, challenging, or complex. These ratings give backcountry users an idea of the risk that is presented by terrain prone to avalanches. In preparation for the Avaluator’s public launch this winter, project manager Pascal Haegeli contracted us to rate popular ski trips beyond national parks boundaries. In addition to this not insignificant challenge, the contract included doing something that had never been done before: developing ATES ratings for snowmobile trips.

The process of assessing ATES ratings requires using the scale’s technical version. The development of this scale is discussed in an excellent article written by Grant and Bruce for the Fall 2004 issue (vol. 70) of Avalanche News. You can also find the ATES technical version on the Parks Canada webpage by entering “avalanche terrain exposure scale” in the keyword search. The technical version employs 11 weighted terrain factors for use by trained professionals to generate ratings that remain consistent from one area to the next and from one assessor to the next.

Karl, who is busy building a house in Revelstoke, landed the easier side of the job—rating the ski trips. Greg, who had only to deal with buying and moving into a new house and planning his own late-August wedding, took on the more complex task of adapting the ATES for sledding trips and rating some popular riding areas. Figuring out how the ATES would work for sledding applications was tough at first, but once that hurdle was overcome, this portion of the project turned out to be fun.

Clearly, rating all ski and sled trips in Canada is a gargantuan task requiring more time and resources than the ADFAR project can muster at this point in its development. Our goal was to first identify general areas where skiers, boarders, and sledders can be regularly found in the backcountry. We decided on these areas based on personal and professional knowledge of the backcountry, our experience as CAC avalanche forecasters, and through dialogue with professional and experienced recreationists in various mountain communities.

We then developed short lists of popular trips commonly traveled by recreationists in these areas. This was done by soliciting opinions from local professional and recreational users. Once we had these trips listed, we looked at our timelines and budgets, and then prioritized the trips to ensure we would geta representative cross-section of trips and tours throughout the Columbia, Coast, and Rocky mountains.

At this point we were ready to begin establishing ATES ratings, thus allowing practical use of the Avaluator in BC and Alberta when it is launched in the fall. Our paths diverged somewhat at this point: Karl sub-contracted people in various areas to carry out further work on ski-touring trips while Greg went into the field to look at snowmobiling terrain and develop the database for sledding trips.

Rating snowmobile trips proved to be a different process than rating ski trips. Sledders differ from skiers due to the nature of the machine, how the users select their terrain, and how much area they cover. Many snowmobile trips also have a groomed or well-established trail in the valley bottom, leading to a cabin or common start point for the day.

These access trails to cabins or common start points were given an overall rating. Then sub-areas were identified, where sledders branch off from the main trail. These sub-areas, generally defined by major terrain features, were then given an overall rating which might differ from the rating given to the access trail. This scheme allows people to assess risk for relatively simple trail riding separately from the risks associated with the subareas, which often include narrower side valleys, higher elevations, or more exposed terrain.

Developing the data for both skiing and sledding included reviewing the trip lists for each region with locals, obtaining basic geographic data (map sheet information, UTM coordinates, access points, etc.) and, of course, assessing an ATES rating for each trip. Clearly not every ski and snowmobile trip was included in this project. We attempted to get trips that are representative of the most-used areas of BC and Alberta but are very aware that much remains to be done. Over time, it is hoped that all trips everywhere will be rated and that resources, such as guidebooks, will include ATES ratings for trips they describe. This way, the ATES ratings will eventually come into general use by recreational backcountry users.

The ATES ratings work done to date will make the Avaluator a useful tool for backcountry recreationists in the coming season. As the task of rating trips continues in the future, the Avaluator will become increasingly effective for more users in more places.

PHOTO: GRANT STATHAM

HOW DID PARKS CANADA DO IT?

The Avalanche Terrain Exposure Scale originated in Parks Canada. Grant Statham, Parks Canada’s Avalanche Risk Specialist, came up with the concept and together with Bruce McMahon, Senior Avalanche Technician at Rogers Pass, they steered the project through numerous consultations. The actual process of rating terrain began in August 2004.

By November of that year 275 ski touring trips in the mountain parks had been rated and the information published. The next summer waterfall climbing was tackled. By November 2005, 75 ice climbs in the national parks had been rated and published. Grant Statham is quick to point out the obvious advantages his team had in rating terrain in the parks.

“To start with,” he explains, “we have an amazing base of knowledge to draw from. We have numerous mountain guides in every park, some of whom have been there for decades. People like Gord Irwin, Marc Ledwidge, Brad White, they know every avalanche path in Banff Park. And there are people like them in every mountain park. It made the terrain discussions so much easier than what the CAC is going through now. Really, there is no substitute for local expertise.”

By Manuel Genswein

1.INTRODUCTION
A variation of companion rescue is performed by clients of commercial guiding, off-piste and helicopter skiing organizations. The experience level of non-commercial back-country users is typically similar and their training level has primarily been achieved by their own motivation and sense of responsibility. Hence during an accident the level of competence amongst buried and non buried subjects is similar. In contrast, the level of responsibility, preparedness and training between clients and guides in commercial operations are hugely different.

By emphasizing “Safety,” some commercial operators create expectations that are difficult to fulfil in the context of ski touring, heliskiing or off-piste skiing. This does not help the clients’ mental preparedness for an accident. The motivation to train their clients is partly due to their own interest and partly due to laws concerning product liability. In countries with harsher product liability laws the training of clients is implemented more thorough than in countries where those laws barely exist. Another interesting fact is the diverging opinion among guides as to the usefulness of training their clients.

Some guides highly value a good base education also for their own good in order to be rescued. Others just hang an avalanche transceiver around the neck of their clients and have resigned themselves to never having a hope of being rescued by them. Because of the hopeless attitude of the latter group, typically their clients don’t get equipped with probe and shovel, which makes a rescue basically impossible. The combination of probe, shovel and transceiver—called “personal rescue equipment”—forms the base of an efficient rescue. This holds true even for commercial backcountry operators. In this context, the potentially rapid availability of rescue equipment—e.g. Helicopter aided companion rescue by heliski companies—is not enough of an excuse to fail in outfitting each client with their individual personal rescue equipment.

The topic of training and equipping clients appears especially important, if one considers that statistically it is the first person to enter a slope, that has clearly a higher probability to release an avalanche than subsequent persons.

2. HOW MUCH TRAINING IS REALISTIC AND ADEQUATE
Central to this discussion is the amount of time needed to adequately train the clients. The threshold for clients and guides is rather low compared to non-commercial groups, where education is a substantial part of the work for a guide.

After extensive enquiries with many commercial guiding, off-piste and helicopter skiing organizations (daily and weekly operators) in regards to an “acceptable” amount of time allocated for client training, the choice for an adequate and practicably possible time frame was 15 minutes. For those operators who have always valued fundamental training, this may appear quite short. For those guides that have “just hung the transceiver around the clients’ neck,” each minute appears to be too much. Ultimately the 15 minute time frame meets the requirement for “acceptance” and “usefulness.” Especially those who see the situation in a rather pessimistic light might put a little more importance into adequate training and personal rescue equipment for clients once they see the rather convincing test results.

Increasing client training time from 15 to 30 minutes would with great likelihood not significantly increase rescue efficiency. In the additional time no great advantages in search and rescue techniques are achieved. A valuable addition would be a short practice of a rescue scenario. Within the chosen time frame it is possible to learn search/ strategy for multiple burials by applying the “marking” feature.

The goal of this project and the field test is to design a training module for client training. After extensive enquiries with many commercial guiding, off-piste and helicopter skiing organizations (daily and weekly operators), the choice for an adequate and practicably possible time frame was 15 minutes. Immediately after the 15 minute training, the clients were asked to search for and excavate two buried subjects in a 50m x 80 m field. Based on the quantitative results of this test, conclusions as to the efficiency of the training module were made and the subsequent module was changed to optimize the content for the next group.

3. TEST PARTICIPANTS
All participants were clients of guides and ski instructors. For the field test the clients were separated from their guides. 83 clients participated in 14 groups. The clients‘ knowledge was varied; most were beginners. The average age was 53; 17 clients were older than 65. Guides were instructed not to hold any special lessons prior to the test. At the time of the test clients knew each other for a couple of hours up to a couple of days.

4. TEST ENVIRONMENT
4.1 Test fields
For efficient data recording, two test fields were used. They were 50m x 80m (see illustration 1), which represents the median size of “survived recreational avalanches” in Switzerland. Slope inclination was approximately 5 degrees in the lower third and up to 20 degrees in the upper end of the field.

Starting point for all rescuers was always a corner at the bottom end of the field (see illustration 1, triangle). In comparison with a typical off-piste avalanche accident this constitutes a significantly more difficult scenario. During an off-piste accident significantly more than 50 % of all rescues are conducted from the top. Foot penetration was between knee and hip deep. This cost the rescuers a significant amount of time and effort, as they were only allowed to move without skis.

Illustration 1

4.2 Buried Subjects
The “victims” were two bags normally used to carry firewood, sewn together and filled with straw. The approximate size per “victim” was 180cm x 70cm. When burying the victims, the snow was stomped down layer by layer. Burial depth was 50 cm – 100 cm, representing the average burial depth in off-piste avalanche accidents. The buried subjects were equipped with remote control avalanche transceivers with probe detection device. Two buried subjects were activated per search, combination A-A or B-B.

5. TEST PROCEDURE AND DATA RECORDING
All groups were lead to the site by their respective guides. Skis and other non-rescue specific gear was left behind. Guests received adequate probes and shovels. Only three-antenna avalanche transceivers with specific “marking” function to eliminate a previously located signal were used in this test. After the group arrived at the site they received a 15-minute instruction. After the short instruction participants were presented with the rescue scenario.

Details recorded:
● Signal search time: The time until the first signal is received.
● Coarse search time: The time from the first point of reception until the signal decreases for the first time as the rescuer walks over the buried subject.
● Fine search time: The time when a clear minimum of distance (or maximum of volume) can be isolated.
● Pinpoint search time: The time when the rescuer hits the buried subject with a probe.
● First visual contact with the buried subject

● Full body free

6. PRACTICAL TRAINING MODULE
The 15-minute training module included the following content:

● General goal and overview

Search procedure including “airport approach”

Mounting of the probe and shovel

● Basic handling of transceiver
“OFF – SEND – SEARCH.”. Switch SEND fg SEARCH two or three times on command, all together, repeat until a routine has been established. Verify after each step, if all participants were able to switched to the appropriate mode.

● Practical search with explanation of each search phase.
Practical search of one buried subject at 35 m distance. Transceiver angled at 45 degrees to group g curved search path, which forces attention on direction indication on transceiver. Flux lines / flux line characteristics not discussed. Clients follow with their transceiver on receive. Group is halted before next search phase to explain the next steps.

● Signal search
If distance to buried subject is greater than range of transceiver g signal search, as per diagram on back of transceiver, is necessary. 3D rotation until signal is detected. Move – no life has yet been saved by just standing still!

● Coarse search
Hold device horizontally “move in direction of arrow.” Does distance indication decrease or increase? At distance 10: airport in sight g slow down!

● Fine search
Approach g slowly and precisely, holding transceiver close to snow surface. Absolutely no grid search! Place shovel at the point of smallest distance indication.

● Pinpoint search with spiral probing (4) up until the “hit” at approximately 1.5 m burial depth. Leave probe in snow. “Mark” with marking function on transceiver; wait until all clients have marked. Activate second transceiver in 15m distance. All guest will locate the second transceiver on their own.

● Excavation
Short explanation of V-shaped snow conveyor. Put clients in V formation while teaching basic concept—“cut blocks” and central snow conveyor belt, paddling motion and correct handling of the avalanche shovel. Actively running of conveyor belt. Explanations and corrections while the clients work. Let conveyor belt run for 3 – 4 min. Practice rotation on command, no specific instructions as to behaviour when first contact with buried subject.

7. RESULTS

 14 groups of 83 clients reached the following median times for locating and completely excavating the buried subjects. Fastest and slowest times were measured as follows: The biggest time lag resulted between the completed excavation of the first buried subject and the start of the fine search for the second buried subject. Those rescuers who did not locate and mark the first buried subject themselves confessed often great difficulty in physically removing themselves from the first buried subject and moving towards the second buried subject, as the distance indication on their transceiver increased.

8. DISCUSSION AND CONCLUSIONS

 The field test results prove that very realistic survival chances exist within a commercially guided group if the guide is buried. The surprisingly short search times make it clear that short and efficient guest training makes sense. The common opinion that a guest cannot ensure the survival of the guide is hereby not accurate and has clearly been proven wrong.

Despite the short training time, the second buried subject was located and excavated in all scenarios. Clearly this result can be attributed to the technically advanced transceivers with marking function. Problems arose for the rescuers who did not mark the first buried subject while transitioning to locate the second buried subject. Those problems indicate that transceivers could further be improved. A basic requirement to achieve the above results is to always outfit clients with modern rescue equipment—probe, shovel and transceiver with “marking” function. The author recommends that instructors use the guidelines and techniques outlined in this paper when training their clients.

The full paper may be downloaded at www.genswein.com

Story and photo by Wren McElroy

“NUMEROUS AND LARGE AVALANCHES IN THE WINTER OF 1971-72 STIMULATED A GROWING INTEREST IN AVALANCHE SAFETY EDUCATION.” – PETER SCHEARER

DID BEING BORN IN 1972 HELP SHAPE MY PASSION FOR AVALANCHE EDUCATION?

OVER THE PAST three years, that passion has helped bring John Tweedy’s vision of using the old highway crew camp at Kootenay Pass as a base for avalanche education to fruition. The combination of easy access to terrain and exposure to an active MOT avalanche control program make the base camp an ideal location for learning. Tweedy was the BC Ministry of Transportation’s first avalanche technician at Kootenay Pass, starting in 1980 and retiring in 2010.

Construction of the highway between Salmo and Creston was begun in the late 1950s; it was opened with ceremony in August 1964. The highway ran right through many kilometres of avalanche paths on both the east and west side of Kootenay Pass. Crews were surprised by the amount of snow on the south facing slopes when they resumed work in the spring—avalanche debris stopped the plow truck drivers from reaching the pass. The original camp for the maintenance crew, equipment operators, plow truck drivers and avalanche technicians was set up in the early 1970s at 1,775m. During a particularly heavy storm cycle, assistant avalanche technician Dave Smith’s truck was buried in the yard, and then run over by a plow. He hitchhiked home.

Early Kootenay Pass professional avalanche courses started in 1979 and ran until 1991, based out of a Creston hotel. A nearby Greek restaurant even created an official training school libation called “the avalanche.” Courses offered included the RTAM Level 1 and Level 2 (Resource Transportation Avalanche Management) and CAA Avalanche Operations Level 1 and 2. During 1981-82, four fully supported manual weather stations were put in place, provided by MOT for the Creston-based courses.

Eventually, the daily 120km drive from Creston proved to be too much and courses at the pass began to wane. Furthermore, the highway maintenance was transferred to a contractor who did not maintain the course snow study plots at the Kootenay Pass summit. Another attempt to hold a Level 1 course at Kootenay Pass was made in the late 1990s, and John Buffery and Marc Deschênes drove from Nelson with students. Days at Kootenay Pass were interspersed with trips to Whitewater, but it was still too much driving.

In 1992, a new building named the Bunkhouse was built, which was a welcome relief from the ATCO trailers that populated the pass. MOT and the road and bridge maintenance contractor manned the building until 2005. When the maintenance contractor started plowing out of Creston, the need for a manned camp at the pass dissolved.

Laura Adams, a CAA Professional Member teaching the Renewable Resource Program at Selkirk College, signed a memorandum with Parks in 2002 to able to teach in Stagleap Provincial Park, but did not use the building. A number of courses for that program were taught up there. I taught a three-day winter camping/RAC course there in 2003 with Laura’s successor Keyes Lessard. Other Selkirk College AST courses were taught there throughout the 2000s, including a course Keyes and I taught for the Department of National Defense. I used the building to teach an all-women AST 2 course I in 2005, and benefitted from a presentation and mock avalanche scenario by Ministry of Transportation. In 2006 and 2008, the RCMP and the Mountain National Park Dog Handlers used the Bunkhouse for Dog Handler Validation courses, which did not seem to impact the day-to-day operations of the avalanche program.

At that time, BC Parks weighed in on the building’s usage. They did not want to see a mountain hostel at the pass; however, they were very supportive of the educational opportunities that could be offered up there. Two BC Parks staff, Dave Heagy, Senior Parks Ranger and Jeff Volp, Area Supervisor, taught AST 1 courses up at the pass for the Ministry of Environment in 2010 and 2011. Participants included Park Rangers and Senior Rangers, Area Supervisors, Conservation Officers, and other Ministry of Environment Staff. All the participants stayed at the Bunkhouse and utilized the classroom, kitchen and living facilities.

In the fall of 2009, John Tweedy and I spoke of starting the CAA Avalanche Operations Level 1 courses again up at the Pass. We agreed on the benefits for the students, instructors and the ITP program to run the courses there. Ian Tomm asked for a proposal. John laughed at the simplicity: the facility is free, the travel is free, it’s all here, he said; bring the students, instructors and a cook and you are good to go. The biggest challenge of a hut-based course is the logistics of the helicopter transport, but at Kootenay Pass, everyone drives there and then they stay. Students and instructors have full days without worrying about driving times, meal preparation or cold students sleeping in the back of trucks. Three years in a row, I missed the first day of teaching a CAA Level 1 course at Kokanee Glacier Cabin because of short December days and difficult weather. At Kootenay Pass, that is not an issue.

In January 2010, students stayed in the Bunkhouse as Course Leader, Mike Rubenstein and I taught the first CAA Level 1. The week was a resounding success, with support from the MOT crew, fantastic catering and good weather. Three Level 1 courses have been run in 2011 and 2012, with positive reviews from all parties involved.

The Bunkhouse can accommodate 13 students, two instructors and a cook, with private rooms and shared washroom facilities. There is a separate kitchen, classroom and inside storage for skis and gear. The MOT avalanche staff maintains a residence as well. A great benefit is the close involvement with the MOT Highways avalanche control program.

A short walk from the building, the Avalanche Technicians have enlarged their existing weather plot; the twice daily weather observations are easy to get to and relevant. Even as we move into the digital age of weather stations, having a professional, manual weather station for students to use adjacent to the Highways weather station certainly enhances the hands-on learning. Anyone can read a digital screen, but to walk out in the cold, dark air of the early morning and read a maximum and minimum thermometer is better for tactile learners.

The elevation of 1,775m is a great starting place for ski tours, and each day progresses further into the terrain. With short travel times, groups are able to get to their study areas, look at terrain and have time to dig their profiles. Some days we were able to travel and dig test profiles on two different aspects. Mid-week we travel to Whitewater Ski Resort, an hour’s drive to the west, where students see another active avalanche program. This provides good linking to lessons—by that point, the students have started using the daily hazard evaluations and drafting snow profiles and they get the opportunity to see all of those skills put into practice. Also, with the easy-access backcountry a short tour from the resort, students are quickly exposed to a different scope of terrain. Whitewater provides one-ride passes for the students and instructors in exchange for ITP credits for Whitewater staff.

Later in the week, Tweedy successor Robb Andersen presents on the MOT avalanche control program. Robb also demonstrates an avalanche rescue scenario with his dog Kilo. A unique benefit to Kootenay Pass is witnessing the Gaz.ex avalanche control in progress. This year we arrived on Sunday, January 29 as a significant storm cycle was occurring. Robb closed the highway at 02:30 in a high hazard. He woke Dave Smith and me up at 05:00 to let us know they were going to do a shoot. Students were in a safe zone on the highway by 05:30 to experience how avalanche hazard is managed and mitigated on the highest all-weather mountain pass in Canada. We could see the flash of the Gaz.ex and hear the rumble of the size 3 and 3.5 avalanches as they buried the highway. Robb’s incredible video footage of control work allowed the students to see the magnitude of what they could hear. The highway remained closed that day until 2:30pm, but the class was secure in the Bunkhouse learning about the nature and formation of avalanches.

Many stakeholders are involved with the operation of the Bunkhouse at Kootenay Pass. BC Parks owns the land, MOT built and owns the building, and the Highways Road and Bridge Maintenance Contractor is responsible for the upkeep of the building. Infrastructure upgrades including potable water, plumbing upgrades and reducing the carbon footprint are in the plans for the coming summer season to allow for continued operation of courses.

Using the Bunkhouse for educational courses is a win-win situation for course participants and the various agencies that take advantage of having their courses at Kootenay Pass.

By Matt Macdonald and Mindy Brugman, Operational Meteorologists at the Pacific Storm Prediction Center, Environment Canada

Figure 1: Infra Red satellite image with superimposed fronts of the storm reaching the coast of BC on December 3rd, 2007 at 03:30UTC.

The 2007-2008 winter season posed a great challenge to the entire Canadian avalanche industry. A large part of this challenge was attributable to persistent weak layers (PWLs). The three major PWLs were the December 3 facets-on-crust layer and the two surface hoar-on-crust layers from January 26 and February 25. The latter two layers were essentially the product of prolonged ridges of high pressure. From a meteorological perspective, the December 3^rd layer was the result of a much more interesting sequence of storms. In Forecasting Snowpack Troublemakers, we take a look at the ingredients of this Pineapple Express-like event, the performances of short and long range numerical weather models as well as recent tools used by the Pacific Storm Prediction Centre (PSPC) for forecasting these types of events.

Let us first define Snowpack Troublemakers. A Snowpack Troublemaker is any disturbance that creates a significant discontinuity in the weather pattern and consequently the snowpack as well, by bringing heavy snow and/ or rain, strong winds, rapid changes in temperatures/freezing levels or prolonged solar radiation/clear nights. It is important to note that it is the speed and intensity at which these elements change that will determine how much trouble the disturbance brings to the snowpack. The December 3 storm was deemed a Snowpack Troublemaker because it met all of these criteria: heavy snow and rain (70cm of snow followed by 25mm of rain in Revelstoke); sustained winds of 100 km/h with gusts up to 150 at many mountain tops; rises of 15oC in 24 hours across much of BC followed by falling temperatures; prolonged sun and clear nights. This sequence of events resulted in a weak layer that persisted throughout the entire season and was linked to many fatalities and several close calls.

Before the influx of moist and mild air typical of a Pineapple Express reached the coast of BC on December 3, an arctic ridge of high pressure centred over the Yukon was in place. This ridge established an arctic flow of cold air across the province and caused the first segment of precipitation to fall as snow. As the upper atmospheric flow switched from northeast to southwest, the overriding warm air sent freezing levels up to 3,000 metres and transformed the falling snow into rain. As the low pressure system stemming from the tropics approached the coast and deepened, winds strengthened from moderate to extreme. When the low hit the coast, heavy snow gave way to torrential rains (Figure 1). Once the low finally moved inland and weakened on December 5, another arctic ridge set up causing the saturated surface to freeze and facets to form subsequently.

Overall, the evolution of the December 3 storm was well handled by numerical weather models. Both the Canadian GEM and American GFS models hinted at the Pineapple Express event four to five days out. This convergence of guidance provided forecasters with a high level of confidence which in turn allowed us to convey the importance of the high impact weather event on the horizon. In recent years, Ensemble Forecasting Systems have become a mainstay tool for the operational meteorologist. These systems are comprised of multiple numerical models and are left to run out into the 10 to 14 day period. The mean of the ensemble members has proven to deliver a more accurate long range forecast than individual model runs. Both the Canadian and the North American Ensemble Forecasting systems did a great job at signaling the characteristics of a Pineapple Express event as early as 12 days prior to the storm striking (Figure 2). Ensembles are hence of great utility for long range outlooks and are being increasingly incorporated into the forecast process.

Figure 2: North American Ensemble forecast for Revelstoke issued on November 23rd, 2007, 11 days before the event. Notice the forecasted amounts of 15 to 20 mm per 12 hour period on the day the storm hit.

Another variable that forecasters at the PSPC have been incorporating into their analysis and prognosis is the Madden Julian Oscillation. The MJO is a tropical disturbance that propagates eastward along the equator in a wave like fashion. Its signal is monitored by surveying the outgoing longwave radiation along the equatorial Indian and Pacific oceans. Essentially, this means keeping an eye on convective activity as well as tropical cyclones. The second essential element to be surveyed is wind anomalies at 200hpa as they are responsible for the development of these storms and potentially delivering the surplus of heat and moisture to mid-latitudes. A significant correlation between the activity of the MJO and the storminess in the Pacific Northwest has been observed throughout the past decade. Thus, there has been increased research and development in forecasting the MJO. The Australian Bureau of Meteorology has created a “spider plot” to conceptualize the position and strength of the MJO. The spider plot has proven to be an excellent tool in monitoring and forecasting the potential of Pineapple Express events such as the December 3 storm.

The short term forecast period remains the primary focus of the Pacific Storm Prediction Centre’s alpine forecast. However, as time permits, long range forecasting tools such as Ensembles and the MJO spider plot will be incorporated to provide avalanche industry professionals with more accurate long range forecasts. As more tools get developed and are verified on an operational basis, forecast lead times for significant weather events such as Snowpack Troublemakers will grow and should help the avalanche industry prepare for storms similar to the one on December 3.

By Laura Maguire and Jesse Percival

WITH UNCOMMON SNOWPACKS BECOMING INCREASINGLY COMMON, PRACTITIONERS IN A COASTAL SNOWPACK HAVE BEGUN DEPLOYING NEW STRATEGIES // JESSE PERCIVAL

COGNITIVE SYSTEMS ENGINEERING (CSE) demonstrates how expert practitioners in high risk/high consequence domains make sense of risk in dynamic, ambiguous and changing conditions. Expert performance is identified as going beyond qualifications to include the ability to activate, organize and flexibly apply knowledge (Woods et al, 2010) in time pressured, goal conflicted and uncertain conditions. To do so involves cognitive work.

Using methods from CSE, this study assessed the operational aspects of snow safety then analyzed the artifacts (tools such as worksheets, websites, whiteboards, InfoEx, etc.) that shape cognition and collaboration. Semi-structured interviews were used to detail how tools are used to make and update forecasts over time. Finally, we elicited examples of surprise, near misses and actual incidents to calibrate findings.

Three prominent, interconnected themes emerged from the research:

1. Much of the cognitive work is not described in the explicit protocols. The formal representations of what constitutes good practice in forecasting is a small fraction of the strategies experts use.
2. The cognitive effort required to manage avalanche risk is a near continuous activity. Forecasting appears to require ongoing calibration. Disruptions to this calibration process have adverse effects on performance.
3. Forecasting is a distributed cognitive task across individuals, teams and the broader industry. Successful forecasting requires distributed practitioners of local team members as well as the resources and insights produced by others within the industry.

PREPARATIONS FOR FORECASTING

Formally, the protocols for a forecaster on duty (FOD) suggests producing a control plan shortly after arriving onsite - but each forecaster interviewed detailed extensive preparations that were not captured by the formal description. A variety of work-related techniques were described. For example, time spent carpooling is used as an informal handoff from one FOD to another to discuss recent activity or control measures. This suggests that formulating the day’s forecast begins well in advance so that a forecaster arrives for duty with a hypothesis of how recent changes in conditions affect their avalanche terrain management.

Shared, off the books activity is a common (and likely necessary) practice not explicitly noted in work procedures and demonstrates a need for ongoing calibration – an example that supports all three findings. It is well documented that forecasting takes place under time pressure. By seeking out data that can help them anticipate conditions in advance, the FOD relieves some of this pressure to lessen the cognitive demands required once they officially clock in.

DISRUPTION, ADAPTATION & SURPRISE

A second example: An unexpected in-bounds release. On this day, the forecasting plan had anticipated instabilities due to temperature changes. After control work, it was expected that normal monitoring would identify if a closure was necessary. However, a personal emergency meant the team was operating one person short. Concurrently, a first aid emergency tied up members who would otherwise be monitoring avalanche terrain. This left the FOD ‘in the bump’ for longer than the usual rotation and his normal practice was interrupted. As expected, the temperature fluctuated and a skier-triggered release occurred in one of the avalanche zones.

This example is informative in two ways. Firstly, it is reflective of what “normal work” is – constantly adjusting to workload demands or unavailability of resources and adapting practices to respond to conditions while balancing inevitable trade-offs. Secondly, this example provides evidence that practitioners construct mental models (Adams, 2005) and continually update them.

MENTAL MODELS

The model is an internal representation of current hazards and an expectation of how this may change over time. Mental models are used to retrieve technical knowledge and to flexibly apply it to variable situations.

In constantly changing conditions, mental models become stale unless continually updated. Referring to the in-bounds avalanche example, the model became insufficient after only a few hours. In the previous example, the forecaster coming back from time off is aware their model is stale and seeks information to recalibrate. LaChapelle (1980) notes a “...prevalent and strong reluctance of working forecasters to experience an interruption in their winter routine…” (pg. 78).

This finding emphasizes organizing work schedules to protect forecasters’ daily and seasonal monitoring routine from interruptions or building in mechanisms to support rapid recalibration or redundancy by cross-checking across other team members.

THE BIG PICTURE - MOUNT WASHINGTON // COLE RAMSHAW

DISTRIBUTED COGNITIVE EFFORTS

Notable as well, is the role of a distributed network in constructing mental models. A diverse range of perspectives informed by different experiences, knowledge and mindsets is needed for accuracy. In the resort, the schedule for FOD’s is designed to provide an overlap day to accommodate the need for distributed cognition. This is an explicit recognition of both ensuring currency of the mental model and the importance of interactions between practitioners. Updating provides an opportunity to draw attention to details and to generate shared insights.

Spatial and temporal constraints also require distributed cognitive efforts. Large terrain and limited daylight hours create time pressures. The FOD relies on technicians to gather and relay data effi ciently and accurately. Without the team, the FOD’s mental model can only partially represent actual conditions.

CONCLUSIONS

Errors by normally high performing experts are insights into how the cognitive demands may become temporarily overwhelming. Studies like this illustrate what aspects of practice should be protected from the pressures of ‘faster, better, cheaper’ common in many workplaces and allows for better engineering of the tools, technologies and protocols used.

Further research can provide an empirical basis for: designing decision support tools; developing training; orchestration & distribution of tasks; funding critical resources; and developing new forms of coordination across networks. Identifying cognitive work in different forecasting settings (mechanized skiing, transportation, industrial) is likely to be useful for accident prevention. In addition, CSE studies comparing expert vs recreational cognition is likely to help public safety efforts.

The authors gratefully acknowledge the Avalanche Canada Foundation for their travel support through the ISSW Fund and the Cora Shea Memorial Fund. For the complete proceedings paper or more information about this and other projects in cognitive work of avalanche forecasting contact Laura (maguire.81@osu.edu) or Jesse (jperceival@mountwashington.ca)

REFERENCES

Adams, L. (2005). A systems approach to human factors and expert decision-making within Canadian Avalanche Phenomena. MALT Thesis. Royal Roads University, Victoria, BC, 284.

LaChapelle, E. R. (1980). The fundamental processes in conventional avalanche forecasting. Journal Glaciology, 26(94), 75–84.

Woods, D., Dekker, S., Cook, R., Johannesen, L., Sarter, N. (2010). Behind Human Error. London: CRC Press.

Alongside many weather monitoring networks and avalanche specific weather monitoring activities CAA members are aware of is a lesser known provincial snow monitoring program. We caught up the current snow survey program coordinator Tony Litke to ask what the program is about and how it can benefit avalanche professionals.

PHOTO: TONY LITKE

TAJ: What is the British Columbia Snow Survey Program (SSP) and how did it come to be?

LITKE: The BC Snow Survey Program was established in 1935 in response to a prolonged drought to monitor snowpacks in BC, and is one of the longest running environmental monitoring programs in the province. It has largely been a cooperative program with federal, provincial and local governments contributing in different capacities over the 80+ years that formal snow surveying has been occurring in BC. Today the major agencies involved are the Ministry of Environment, Ministry of Forests, Lands and Natural Resource Operations and BC Hydro. The program also receives monitoring assistance from some local governments and a few private sector companies.

TAJ: So in a nutshell, what is snow surveying?

LITKE: A snow survey is extremely simple in its nature: a surveyor travels to a site and inserts a specifically designed long aluminum pipe into the snowpack at five to 10 set locations. The pipes are weighed and the average snow depth and snow water equivalent (SWE) recorded. This is performed on predetermined schedules one to eight times per year. Traditionally this data is then correlated to downstream rivers to model and predict water flows and assist with water management.

TAJ: Where are the SSP monitoring sites?

LITKE: Manual snow courses and automated snow weather stations are usually at higher elevation locations, typically between 1,000m and 2,300m. They're found around the entire province from the northern Rockies to the coast to the Kootenays to the Okanagan and everywhere in between. Often they are strategically positioned to correspond with specific drainages and watersheds.

TAJ: How has technology changed the snow survey program?

LITKE: The advent of computers, weather monitoring instrumentation and satellite telemetry has slowly but drastically changed the way we survey snow, starting in 1969 when the first snow pillow and automated data collection platform was installed at Mission Creek near Kelowna. Despite the early start, widespread automation of manual snow survey sites really didn’t really gather momentum until the mid-90s and has been ongoing ever since. Nowadays most automated sites measure and report temperature, cumulative precipitation, snow depth and snow water equivalent on hourly intervals, 24 hours a day, 365 days a year. The most recent development has been the emergence of snow scales as a viable alternative to fluid filled snow pillows, which has made construction and deployment of new

sites far less cumbersome.

TAJ: What are some problems involved with trying to keep track of how much snow there is across BC?

LITKE: Where to begin! I always tell people snow surveys are the hardest simple thing you will ever do. First of all, as we all know snow packs can be extremely variable over very small geographic areas. With manual surveys, human and site specific factors greatly influence the results, and these are extremely hard to control for. Given the remote location of most of the sites you never know what you are going to get until you get there. When it comes to the automated weather stations, lightning, wildfires, snow creep, falling trees, critters, bears and vandalism all conspire to push stations off the air. It’s definitely more challenging than maintaining a weather plot in a resort or roadside setting, because due to their far flung locations we can’t easily visit the sites to see what is going on and often only get to visit them a couple times a year. Thankfully, as time has progressed monitoring technology and reliability have greatly improved to the point where the electronics typically operate problem free.

TAJ: Can you give us a snapshot of the program today?

LITKE: After a few years hiatus there has been a push in recent years to continue to automate manual snow courses resulting in the construction of six new automated snow weather stations this past summer. That brings the total number of automated sites to 76 across the province, in addition to manual snow surveys happening at 158 active sites. This season over one million discrete snow measurements will be recorded across the SSP.

TAJ: How can CAA Members use make use of the SSP data?

LITKE: All the data the snow survey program produces is publicly available, including the historical archives dating back to 1935, and ongoing hourly near-real-time data. Some of the sites are already replicating data into the InfoEx or various other enthusiast-maintained websites. The snow survey program is in the process of creating a new map-based platform to share data that should hopefully go live in early 2017. In the meantime the data is available through the river forecast centers webpage in tabular format at bcrfc.env.gov.bc.ca/data/index.htm.

The snow weather stations all broadcast hourly data, so it is useful for any sort of weather reconnaissance you might need, from determining how a weather system moved through a mountain range to whether or not there is some fresh powder at your favorite touring haunt. We receive all sorts of enquiries from around the world, from power traders in the states betting on the markets that depend on water supply, to the strangest call I remember which was an RCMP detachment looking to find out whether it snowed in a certain area on the day a robbery occurred to aid an investigation. In summer time people are often interested in when the snow has disappeared so they can decide if it is mountain biking season. One advantage of the snow survey program weather station data is that it is year-round, so when the ski hills and backcountry lodges stop updating their websites and submitting to InfoEx, our data keeps rolling in.

TAJ: What does a typical day for you look like?

LITKE: A typical day...is there such a thing? It really depends on the time of year and what is going on. Normally the first thing I do on any given day is take a look at all of the snow weather stations to check that everything is functioning correctly. We aim to visit each site a minimum of twice a year, so a lot of planning and effort goes into those logistics. In the summer once the snow is gone we do all our repair work and any new installations, so depending on the year there might only be a few snow-free months to accomplish a lot of work.

In the winter we like to stop in and make sure everything is functioning like we expect based on what we see on site. I also receive a lot of emails everyday, so I spend a good chunk of my time in the office working with the more than two dozen different cooperating groups that operationally help us deliver the program. My favorite days are the ones in the winter where it’s snowing heavily, time slows down a bit, and everything just seems to be quiet and serene on site. One thing is for sure, every day is different, and every day has a new challenge.

TAJ: Why has this been one of the longest running monitoring programs and how is the data being used for decision making?

LITKE: Water supply forecasting is the primary driver for the program and the impacts range from public safety to economics. From power generation forecasting, flood forecasting, drought monitoring or irrigation planning, decision makers need to know how much snow is in the mountains because it will eventually become water in our lakes and rivers. The more information, and the more accurate the information is, the better the decision making will be. This has been important for decades and will continue to be, which explains why the program has had such a long and healthy life. Of course climate change is another big driver and being able to keep tabs on what is going on in remote mountainous regions over the long term will become more and more important on the horizon There is not yet technology on the horizon that is immediately able to take over in-situ weather monitoring, so it is likely the snow survey program will still be around for some time.

From vol. 103, spring 2013

By Jeff Boyd (a,b), Hermann Brugger (b,c), Fidel Elsensohn (b), and Peter Paal (b,d)

a) Department of Emergency Medicine, Mineral Springs Hospital, Banff, AB, Canada; International Federation of Mountain Guides

b) International Commission for Mountain Emergency Medicine ICAR MEDCOM

c) Institute of Mountain Emergency Medicine, EURAC Research, Drususallee 1, I-39100 Bozen/Bolzano, Italy

d) Department of Anaesthesiology and Critical Care Medicine, Innsbruck Medical University, Anichstrasse 35, A-6020 Innsbruck, Austria

AIRWAY PATENCY. IN BURIALS LONGER THAN 35 MINUTES, THE PATENCY OF A VICTIM'S AIRWAY BECOMES A CRITICAL OBSERVATION. IF THE AIRWAY IS PATENT THE VICTIM MAY SURVIVE, EVEN IF THEY ARE IN CARDIAC ARREST DUE TO HYPOTHERMIA. // HERMANN BRUGGER ARCHIVES

BACKGROUND

Medical management recommendations (Brugger et al., 2004; Brugger and ICAR1, 2006) have been previously based on concepts extrapolated from the avalanche survival curve derived from biostatistical analysis (Falk et al., 1994). A recent study comparing Canadian to Swiss survival produced similar sigmoidal-shaped curves (Fig. 1)(Haegeli et al. 2011).

The initial “survival phase” was shorter in western Canada due to greater mortality from trauma. Thereafter, survival plummeted in both series during the asphyxia phase, ending at 35 minutes burial, with mortality greater in Canada due to denser snow.

Deducing that victims unable to breathe had succumbed to asphyxia at the end of this 35 minutes, while those with a patent airway and an air space could survive longer until death from hypothermia at 90 minutes, the International Commission for Mountain Emergency Medicine (ICAR MEDCOM) published resuscitation recommendations and a management algorithm (Brugger et al., 2001).

However, this analysis did not consider actual clinical experience. The first systematic review of clinical evidence for these recommendations confirmed that duration of burial, airway patency, core temperature and serum potassium levels were reliable predictors of survival (Boyd et al., 2010) and, after expert review by the International Liaison Committee for Resuscitation (ILCOR), were included in the 2010 BLS and ALS2 Resuscitation Guidelines for North America and Europe (Soar et al., 2010; Vanden Hoek et al., 2010).

Although current adoption of these recommendations approximates 75%, there are substantial failures, notably in initiation or withholding of CPR and triage to extracorporeal circulation rewarming (heart-lung bypass) (ECR) (Brugger, 2011). Additionally, recent research in avalanche trauma (Hohlrieder et al., 2007; Boyd et al., 2009), survival analysis (Haegeli et al., 2011) and hypothermia management (Brown et al., 2012) has shifted emphasis.

FIG. 1: OVERALL SURVIVAL CURVES FOR PEOPLE COMPLETELY BURIED IN AVALANCHES IN CANADA (N = 301) AND SWITZERLAND (N = 946) FROM OCT. 1, 1980, TO SEPT. 30, 2005, BY DURATION OF BURIAL (DUMBGEN COMPARISON: P = 0.001). THE DOTTED LINE REPRESENTS THE CANADIAN SURVIVAL CURVE INCLUDING ONLY ASPHYXIA-RELATED DEATHS (N = 255). EXTRACTED FROM HAEGELI ET AL., 2011.

METHODS

A structured clinical-literature review of the components of the 2001 algorithm was performed using an ILCOR worksheet format after establishing subject matter, objectives and inclusion/exclusion criteria a priori at a TOPIC meeting of the ICAR MEDCOM. This format examined each of 27 components using individual PICO (population, intervention, comparator, outcome) questions as well as 10 general questions. Findings were presented by the working group to a SCIENCE meeting of the ICAR MEDCOM for expert debate, and consensus recommendations were developed at a MANUSCRIPT meeting in October 2011.

RESULTS

Keyword- and hand-searching found 3,530 publication citations in the peer-reviewed clinical literature of which 96 articles were scrutinized in detail for content, study design and methodological quality. Thirty-seven recommendations were developed, classified for benefit and a simplified algorithm was developed. These recommendations and an algorithm (Fig. 2) for ALS personnel have been published (Brugger et al., 2012). Below is an abridged text oriented to both BLS and ALS rescuers.

GENERAL RECOMMENDATIONS

Safety and welfare

The safety and welfare of rescuers and all others remain paramount.

Companion and organized rescue

Prompt extrication with initiation of BLS resuscitation remains the priority for companions. Organized rescue is best mobilized early, ideally by helicopter, with rescue-trained emergency physicians or paramedics equipped with critical medical and safety kit, plus dogs with handlers.

Airway patency and air pocket

Rescuers are to dig from the side and, in burials longer than 35 minutes, note whether the airway is patent +/- an air pocket present.

General measures

To mitigate against the common rescue collapse from cardiac arrhythmias, hypothermic victims are best managed gently, with minimal truncal and limb movements, without rough motion or inappropriate chest compressions, and kept in a horizontal position.

Dry insulation includes insulation from the snow surface as well as from continued conductive, convective and radiant heat loss. Assemblies include blankets, padded rescue bags and outer windproof and waterproof reflective foils. Wet clothing may be replaced with dry layers if efficient although adding thick insulation over wet clothing is equally effective and usually more practical (Henriksson et al., 2012).

Field rewarming is principally prevention of further heat loss plus chemical heat packs, although more sophisticated rewarming with specific equipment may be indicated if evacuation is prolonged. Heated humidified inspiratory air or oxygen requires field-usable equipment and does not greatly reduce heat loss but may be indicated in prolonged transports.

Oxygen is indicated for any degree of asphyxia and will reduce the risk of arrhythmias in hypothermia (Danzl, 2012). Pulse oximetry may be unreliable with cold extremities and device malfunction from the cold, bright light and high altitude (Luks and Swenson, 2011).

Monitoring

Victims of significant involvement are best monitored throughout evacuation and ideally from the moment they are exposed. This includes electrocardiographic (ECG) monitoring with an AED or monitor-defibrillator. Core temperature is most reliably measured in the lower oesophagus in victims that have an endotracheal tube (tube in the trachea) in place. A medical thermistor probe is preferable although inexpensive probes from indoor/outdoor thermometers can be sufficiently accurate (Pasquier et al., 2012). Epitympanic (ear drum temperature) probes are accurate if used appropriately (Walpoth et al., 1994). Rectal temperatures provide a reasonable initial temperature (Danzl, 2012) although require undressing the victim and lag during rewarming. Other temperatures are likely unreliable. Clinical staging is unreliable if asphyxia or trauma impairs mentation.

Airway management and ventilation

An unresponsive victim without an advanced airway is best transported in the recovery position with the cervical spine stabilized as well as possible. Airway interventions have low risk of inducing arrhythmias and include oropharyngeal airways as well as advanced airways such as endotracheal intubation or supraglottic airways (such as the laryngeal tube). Advanced airways protect against aspiration of vomitus and allow better victim access and spinal stabilization with the victim supine.

Ventilation is indicated when breathing is inadequate and always with chest compressions in CPR.

Trauma management

Pneumothorax is managed with needle thoracostomy (large-bore needle through the chest wall) or open thoracostomy (hole through the chest wall), ideally in a victim that is ventilated with an advanced airway.

Severe limb bleeding is managed with tourniquets. Other trauma modalities additionally include splinting, wound care, analgesia and antibiotics for open fractures.

Trauma victims are best transported to the medical centre that is most appropriate for their injuries, directly to a dedicated trauma centre3 if severe.

MANAGEMENT SCENARIOS

Alert victim

These are normothermic or mildly hypothermic. After assessment add insulation with or without changing wet clothing and allow active movement that will likely be sufficient to rewarm them. They may ingest warm clear sugar-containing fluids that are not alcoholic or strongly caffeinated so long as they are not likely to require sedation or anaesthesia in less than two hours and not significantly injured. Oral fluids will maintain hydration, especially if evacuation is delayed or prolonged.

If the involvement was clearly not life-threatening, then a decision may be made for them to remain in the field. However, if the involvement was potentially life-threatening they are best evacuated to the nearest emergency department for advanced assessment and observation as delayed complications may occur.

Poorly responsive victim with vital signs

These are asphyxiated +/- moderately or severely hypothermic. They are to be closely monitored, ideally with ECG monitoring as early as possible due to the risk of rescue collapse and arrhythmia. Core temperature will be very useful especially for disposition decisions. All general measures and other management modalities become critical.

Transport to the nearest hospital for advanced assessment, intervention and observation is indicated. If significantly asphyxiated, this would best be a hospital with an ICU. Seriously injured victims are best transported directly to a trauma centre. Hypothermic victims need rewarming with modalities such as the forced-air rewarmers most commonly used in surgical programs. However, if there is evidence of cardiac instability, such as ventricular arrhythmias on the ECG, or if the core temperature is <28°C (less than 28°C) direct transport to a centre4 with advanced extracorporeal rewarming (ECR), such as cardiopulmonary bypass, is preferable due to the risk of cardiac arrest during rewarming.

Victim with no vital signs with burial duration less than 35 minutes

These are asphyxiated and only mildly hypothermic. If lethal trauma is found, such as unsurvivable decapitation or truncal transection, resuscitation is withheld. Otherwise, prompt exposure and extrication with BLS including ventilations, with AED/ECG monitoring and defibrillation if indicated/prompted, +/- ALS are started expediently.

If clinical improvement results from resuscitation or any cardiac rhythm is seen on ECG or an AED prompts defibrillation, then resuscitation should continue to the nearest hospital, ideally with an ICU. If no improvement is found after 20 minutes of resuscitation and only asystole (flat line) has been seen on ECG or an AED does not prompt defibrillation then resuscitation may be terminated in the field (Soar et al., 2010; Vanden Hoek et al., 2010; Paal et al., 2012).

Victim with no vital signs with burial duration more than 35 minutes

These have suffered cardiopulmonary arrest from prolonged asphyxia or hypothermia. If lethal trauma is found or the whole body is frozen, resuscitation is withheld.

If they have an obstructed airway they have arrested from prolonged asphyxia, which after 35 minutes has a very poor prognosis, and resuscitation may be withheld (Soar et al., 2010; Vanden Hoek et al., 2010).

If the airway is patent they may have arrested from prolonged asphyxia with the resultant poor prognosis; but alternatively they may have been able to breathe and the arrest may have been from significant hypothermia and the victim may therefore be salvageable. Therefore, if the core temperature is found >32°C they are principally asphyxiated and a resuscitation attempt may be initiated but terminated if no improvement is noted after 20 minutes and only asystole is seen on the ECG or an AED does not prompt defibrillation. But, if the core temperature is <32°C then arrest may be from hypothermia and resuscitation is continued and the victim is transported preferably to a centre with ECR5. If the duration is not known and understanding that a core temperature of <32°C can only occur after at least 35 minutes of cooling, a core temperature of <32°C may therefore be a surrogate for burial longer than 35 minutes (Boyd et al., 2010; Vanden Hoek et al., 2010).

CPR is not modified for hypothermic arrest victims although a longer check of 60 seconds for vital signs is indicated as pulses may be indistinct. Persistent breathing or movement should prompt “watchful waiting” but if no signs of life are found then CPR is best started and continued. Defibrillation is performed if prompted by AED or indicated by ECG although repetitive defibrillation (over three attempts) may not be successful due to the cold heart being very irritable. ALS medications have only been shown effective in animal studies so judicial use is appropriate (Brown et al., 2012). No intervention is to delay transport of hypothermic arrest victims. Note is made that successful rewarming has resulted in good survivals after prolonged CPR of up to six and a half hours (Brown et al., 2012).

If the duration of burial or the status of the airway is unknown or a prolonged transport to ECR is being considered, then a serum potassium level (K+) at an emergency department, best in the direction of the ECR centre, may assist. If the K+ is <8mmol/L then survival is possible vs. >12mmol/L which is not survivable (Boyd et al., 2010; Soar et al., 2010; Vanden Hoek et al., 2010; Brown et al., 2012). A K+ between 8 and 12mmol/L may assist in a decision made with consideration of all factors.

VICTIMS WITH NO VITAL SIGNS THAT ARE BURIED LONGER THAN 35 MINUTES BUT THAT HAVE A PATENT AIRWAY ARE LIKELY TO HAVE SUFFERED A CARDIAC ARREST FROM SEVERE HYPOTHERMIA AND ARE BEST TRANSPORTED TO EXTRACORPOREAL RE-WARMING WITH HEART-LUNG BYPASS. // INNSBRUCK MEDICAL UNIVERSITY ARCHIVES

TRIAGE

Where multiple victims exceed available resources then triaging becomes necessary, especially when other victims remain buried. Victims without vital signs, especially if in asystole, are far less likely to survive and place high demands on resources. Victims exhibiting major trauma that appears likely lethal are not likely to survive. Extremely hypothermic victims, especially if their core temperature is the same as ambient temperature and is less than 10°C, are unlikely to survive. A triage algorithm for avalanche incidents that incorporates avalanche and triage concepts has been published (Bogle et al., 2010).

CONCLUSION

Important field recommendations range from simple evidence-based victim-handling measures to integrating critical factors in crucial decisions that include prehospital termination of resuscitation. Advanced airway use as well as AED and core temperature monitoring are more relevant with improved training of avalanche professionals. Trauma management includes the use of tourniquets as well as decompression of pneumothorax. Triage of multiple victims on-site, and those severely hypothermic to appropriate centres, is enabled using the integrated avalanche resuscitation algorithm.

CONFLICT OF INTEREST

None of the authors have any financial conflict of interest. All authors have published on mountain medicine.

REFERENCES

Bogle, L.B., Boyd, J.J. and McLaughlin, K.A., 2010. Triaging multiple victims in an avalanche setting: the Avalanche Survival Optimizing Rescue Triage algorithmic approach. Wilderness Environ Med, 21(1): 28-34.

Boyd, J.J,, Brugger, H. and Shuster, M., 2010. Prognostic factors in avalanche resuscitation: a systematic review. Resuscitation, 81(6): 645-652.

Boyd, J.J., Haegeli, P., Abu-Laban, R.B., Shuster, M. and Butt, J.C., 2009. Patterns of death among avalanche fatalities: a 21-year review. CMAJ, 180(5): 507-512.

Brown, D.J., Brugger, H., Boyd, J.J and Paal, P., 2012. Accidental hypothermia. New England Journal of Medicine, 367(20): 1930- 1938.

Brugger, H., 2011. Avalanche accidents: ILCOR Guidelines 2010 & ICAR MEDCOM algorithm. Proceedings ICAR General Assembly, Are, Sweden.

Brugger, H., Durrer, B., Adler-Kastner, L., Falk,. M. and Tschirky F., 2001. Field management of avalanche victims. Resuscitation, 51(1): 7-15.

Brugger, H., Durrer, B. and Boyd, J.J., 2004. On Site Treatment of Avalanche Victims. Avalanche News, 71(Winter 2004-05): 30-33.

Brugger, H., Durrer, B., Elsensohn, F., Paal, P., Strapazzon, G., Winterberger, E., Zafren, K. and Boyd, J.J., 2012. Resuscitation of avalanche victims: Evidence-based guidelines of the international commission for mountain emergency medicine (ICAR MEDCOM): Intended for physicians and other advanced life support personnel. Resuscitation, 2012 Nov 2. pii: S0300- 9572(12)00876-3. doi: 10.1016/j.resuscitation.2012.10.020. [Epub ahead of print]

Brugger, H. and International Commission for Alpine Rescue, 2006. Time is Life - medical training in avalanche rescue. IKAR-CISA : Newport Music [distributor]

Danzl, D. F., 2012. Accidental Hypothermia. Wilderness medicine. Auerbach P. S.. Philadelphia, Mosby Elsevier: 116-142.

Falk, M., Brugger, H. and Adler-Kastner, L., 1994. Avalanche survival chances. Nature, 368(6466): 21.

Haegeli, P., Falk, M., Brugger, H., Etter HJ and Boyd J.J., 2011. Comparison of avalanche survival patterns in Canada and Switzerland. CMAJ, 183(7): 789-795.

Henriksson, O., Lundgren, P., Kuklane, K., Holmer, I., Naredi, P. and Bjornstig, U., 2012. Protection against Cold in Prehospital Care: Evaporative Heat Loss Reduction by Wet Clothing Removal or the Addition of a Vapor Barrier-A Thermal Manikin Study. Prehosp Disaster Med, 27(1): 53-58.

Hohlrieder, M., Brugger, H., Schubert, H.M., Pavlic, M., Ellerton, J. and Mair, P., 2007. Pattern and severity of injury in avalanche victims. High Alt Med Biol, 8(1): 56-61.

Luks, A. M. and Swenson, E.R., 2011. Pulse oximetry at high altitude. High Alt Med Biol, 12(2): 109-119.

Paal, P., Milani, M., Brown, D., Boyd, J.J. and Ellerton, J., 2012. Termination of Cardiopulmonary Resuscitation in Mountain Rescue. High Alt Med Biol, 13(3):200-8.

Pasquier, M., Rousson, V., Zen Ruffinen, G. and Hugli O., 2012. Homemade thermometry instruments in the field. Wilderness Environ Med, 23(1): 70-74.

Soar, J., Perkins, G. D., et al., 2010. European Resuscitation Council Guidelines for Resuscitation 2010 Section 8. Cardiac arrest in special circumstances: Electrolyte abnormalities, poisoning, drowning, accidental hypothermia, hyperthermia, asthma, anaphylaxis, cardiac surgery, trauma, pregnancy, electrocution. Resuscitation, 81(10): 1400-1433.

Vanden Hoek, T. L., Morrison, L. J., et al., 2010. Part 12: cardiac arrest in special situations: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation, 122(18 Suppl 3): S829-861.

Walpoth, B.H., Galdikas, J., Leupi, F., Muehlemann, W., Schlaepfer, P. and Althaus, U., 1994. Assessment of hypothermia with a new "tympanic" thermometer. J Clin Monit, 10(2): 91-96.

1) International Commission for Alpine Rescue

2) BLS = Basic Life Support; ALS = Advanced Life Support.

3) For example - Vancouver General Hospital, Royal Inland Hospital in Kamloops, Kelowna General Hospital or Foothills Medical Centre in Calgary.

4,5) For example - Vancouver General Hospital, Foothills Medical Centre in Calgary or University Hospital in Edmonton. Near future - Kelowna General Hospital

By James Floyer

INTRODUCTION

High resolution penetrometer technology has been around for a while now. The first analogue instrument was made in the 1970’s (Bradley’s resistograph) and a digital version was made a decade later (Dowd and Brown’s digital resistograph). Over the years a handful of instruments have appeared, hoping to lure practitioners into plunging probes into the snow and wean them off the laborious habit of digging pits. Although there still seems to be a lot of enthusiasm surrounding penetrometer technology, in practice the luring and the weaning just hasn’t happened yet.

While these fancy instruments have excited researchers with their ability to objectively and rapidly measure snowpack properties (most that have been produced measure hardness, some measure density), there are some good reasons why snowpack penetrometers have not found their way into everyday, mainstream snow assessment practices. One reason is cost. Personally, I don’t put too much store on this, as I firmly believe that people would be willing to pay quite a bit of money for an instrument if it made the task of assessing snowpack stability faster and/or more certain. Instead, I believe the more important reason is that we haven’t yet figured out how to reliably identify weak layers of interest (critical weak layers) from the penetrometer signals.

The study summarized here (see Floyer (2008, pp. 129-151) for a more detailed account) makes a step towards the goal of detecting critical weak layers by relating the shape of the penetrometer signal at a weak layer to the fracture character of that weak layer determined from a nearby compression test. Using the premise that weak layers that fall into the sudden fracture character category can be considered of critical interest, a scheme is presented that allows for this discrimination to be made. The scheme does require the weak layer to be pre-identified, so essentially this scheme is a method for determining the importance of a weak layer that has already been defined. At the University of Calgary, we have also been making progress towards weak layer detection, but for now, I’ll focus on the fracture character study.

METHOD

The penetrometer profiles for this study were collected using a modified SABRE penetrometer (Mackenzie and Payten, 2002) manufactured by Himachal Safety Systems. This manually driven instrument records force-resistance with depth at a frequency of 1000 Hz. The analytical techniques used here could readily be applied to data collected using other digital force-resistance penetrometers.

Compression tests were carried out in close proximity to the penetrometer profiles and the fracture character and depth of each fracture was recorded. In total, 78 penetrometer profiles and 56 compression test results were collected from 28 different site-days and 16 unique sites during the winter of 2007-2008. A typical test configuration is shown in Figure 1.

From the penetrometer profiles, weak layers (with thickness) or interfaces (with no thickness) were manually identified in the penetrometer signals using the depth information from the compression test results. Due to inaccuracies in the depth information associated with both penetrometer and compression test measurements, the weak layer/interface was interpreted in the penetrometer signal up to ±2 cm from the depth recorded in the compression test. Two examples of interpreted penetrometer pushes are shown in Figure 2. Fractures in very low resistance snow could not be identified, due to the SABRE penetrometer’s inability to measure fist resistance snow.

In total, 83 weak layers/interfaces (hereafter referred to as weak layers) were identified in the penetrometer signals. Of these, 41 were resistant planar fractures, 20 were sudden collapse, 14 were non-planar breaks, seven were sudden planar, and 1 was a progressive compression. Due to the low numbers of sudden planar and progressive compression fractures, it was decided to combine the classes into sudden fractures (sudden collapse and sudden planar) and others (resistant planar, non-planar breaks and progressive compression); this grouping reflects the higher incidence of skier-triggered avalanches associated with sudden fractures (van Herwijnen and Jamieson, 2007).

A number of variables were extracted from the penetrometer signals associated with and surrounding the interpreted weak layers. These variables are shown in Table 1. Some of the variables were tested at a number of different distances away from the top and bottom of the weak layer, since, for these variables, the optimum distance from the weak layer was unknown.

A univariate analysis was used to determine the variables that showed the greatest amount of difference in the signals associated with sudden and other groups of fractures. The best variables from the univariate analysis were selected for inclusion in a linear discriminant analysis. Discriminant analysis provides further information on the power of the variables to discriminate between the sudden and other groups, as well as giving a scheme for combining the variables and classifying the penetrometer signal into the sudden and other group.

RESULTS

The variables selected from the univariate analysis for inclusion in the discriminant analysis are shown in Table 2. The second column in this table shows the factor structure coefficients from the discriminant analysis, which gives a measure of the relative importance of each variable for discriminating between the sudden and other fracture character groups.

From the discriminant analysis results, weak layer thickness contributes the most to group separation, with thick layers selecting for sudden fractures. This has an intuitive explanation that thick weak layers are associated with sudden collapse fractures, which, in this analysis, account for the bulk of the sudden fractures. The variable with the second greatest contribution to group discrimination, maybe surprisingly, is the maximum hardness gradient up to 5 mm below the weak layer. For this variable, the absolute value for the maximum was used, so the positive value means that a greater maximum hardness gradient selects for sudden fractures. The average hardness gradient 20 mm below the weak layer also contributes to discrimination, although to a lesser extent. These two variables combined indicate that a stiffer substratum may favour sudden fractures.

Both the average gradient and the maximum gradient 20 mm above the weak layer also contribute to group separation, with factor loadings of -0.42 and 0.32 respectively. The negative value for the average gradient is associated with the negative average gradient values above the weak layer (generally a decrease in hardness with an increase in depth); so a higher negative value still indicates that higher values are associated with sudden fractures. These variables relate to the generally accepted view that a stiffer layer of snow above the weak layer is important for fracture propagation (van Herwijnen and Jamieson, 2007).

The discriminant function built using standardised function weights (not shown, see Floyer (2008, p. 164)) was used to classify the weak layer/interfaces identified in the penetrometer signals into sudden or other fracture character groups. Using a leave-one-out cross-validation method, 77.8% of sudden fractures were correctly classified and 81.5% of other fractures were correctly classified. The overall prediction rate was 79.6%. Classification parity was good between the two groups.

SUMMARY

A method for predicting the broad fracture character group (sudden or other) from penetrometer signals has been developed, based on a multivariate statistical analysis of penetrometer signals interpreted against fracture character results from nearby compression tests. Using a leave-one-out cross-validation method, overall classification rates of approximately 80% were achieved. Weak layer thickness, maximum hardness gradient 5 mm below the weak layer and the average hardness gradient 20 mm above the weak layer contributed the most to discriminating between the two groups.

Results for the sudden category were likely biased towards sudden collapse fractures, which dominated the data set used in this study. More observations are necessary to be able to distinguish between sudden collapse and sudden planar fractures in the sudden category, as well as between the resistant planar, progressive compression and non planar break fractures within the other category. There are also concerns over the subjective nature of the penetrometer signal interpretation, although this was mitigated by setting limits on the window in which the weak layer could be identified.

These results are promising, since they indicate that weak layers may be classified on the basis of fairly simple parameters extracted from the penetrometer signal. If combined with layer detection methods and possibly micro-structural information from higher resolution penetrometers (such as the SnowMicroPen), we move closer to the possibility of automated critical weak layer detection from penetrometer signals.

ACKNOWLEDGMENTS

I would like to thank Bruce Jamieson, who supervised my degree at the University of Calgary. I would also like to thank the entire ASARC crew, the staff at a great number of operations in BC and AB, and the various financial supporters of the ASARC program.

REFERENCES

Floyer, J. A., 2008. Layer detection and snowpack stratigraphy characterisation from digital penetrometer signals, (Ph.D. thesis), Dept. of Geoscience, University of Calgary, Calgary, Canada.

van Herwijnen, A. and B. Jamieson, 2007. Fracture character in compression tests, Cold Regions Science and Technology, 47(1-2), 60–68.

Mackenzie, R. and W. Payten, 2002. A portable, variable-speed, penetrometer for snow pit evaluation, Proceedings of the International Snow Science Workshop (2002: Penticton, BC), 294–300.

By Lisa Larson

FIG. 1: ICAM RISK MANAGEMENT CHART

IN 2008, WE BEGAN TRACKING HIGH-POTENTIAL INCIDENTS, which are defined as incidents that have a reasonable likelihood to cause or have caused a significant but not life-altering injury to a worker. In 2013, we standardized our approach for identifying the root causes and contributing factors for such incidents through a technique called the Incident Cause Analysis Method (ICAM).

ICAM involves the identification of systemic health, safety or environmental deficiencies. It outlines an investigative process and a set of tools that consider, but also look beyond, human error and examines all of the contributing factors leading to incidents. It also enables the development of recommendations aimed at preventing incidents from re-occurring. (www.teck.com, 2014)

Incident investigation starts with good data collection. Putting a team together that includes members with technical or operational experience relevant to the nature of the event, with no potential conflict of interests with the investigation. Once assembled, the group determines which data needs to be collected. The collection of data covers five categories: People; Environment; Equipment; Procedures/ Documents; and Organization (PEEPO). This first round of data collection can result in a mountain of information; each piece needs to be analyzed to determine if it is verified as fact and it contributed to the event, for example, the incident occurred at 18:30 hours (fact); the sun was low in the sky making the track difficult to see (contributing factor).

The next step is to organize the data by creating a timeline using the relevant information from the initial evidence gathering. Descriptions are recorded with a timestamp, where available, for any observed action or inaction that may contribute to the timeline. Constructing a detailed chronology provides a clear picture for the investigation team of events leading up to, before and after the incident.

Once the timeline is in order, the team works through each event and determines if it did indeed contribute to the incident. Where events have contributed to the incident, the team performs a process called 5 Whys. Beginning with why did it contribute, the process then continues to ask why, until it arrives at one of three possibilities:

• A point of control
• A point beyond control
• A point that requires further information to answer “why?”

The 5 Why process will help identify organizational factors/root causes of an incident by encouraging the team to avoid assumptions/biases and dig deeper into the conditions that led to each contributing factor.

The ICAM process is then used to pinpoint underlying causes of the incident, rather than focus on potential errors of the people involved. ICAM is based on principles developed by James Reason, an expert in human factors and author of many books on the subject. James Reason also developed the Swiss cheese model as a metaphor for how incidents occur.

Each layer of cheese represents defenses in our safety systems. Ideally each layer would have no holes, but defenses are like Swiss cheese. A hole in one layer may not cause an incident, however, when holes in the defenses align briefly, it provides opportunity for an incident to occur.

Holes occur for two reasons:

• Active Failures: Errors and violations having immediate negative results, usually caused by an individual

• Latent Failures: Caused by circumstances such as scheduling problems, inadequate training, or lack of resources. Latent failures can lay dormant in the system for many years before combining with active failures to provide opportunity for an incident to occur (AviationPros, 2006)

FIG. 2: SAFETY WISE SOLUTIONS INCIDENT INVESTIGATION REFERENCE GUIDE, NOVEMBER 2006

Having organized the data to create a timeline, probed contributing events using the 5 Why process to pinpoint underlying causes, the next steps in the ICAM process are to classify factual information in order to identify:

• Absent and Failed Defenses
• Individual/Team Actions
•  Task/Environmental Conditions
• Organizational Factors

Once the information is classified, the team must develop clear recommendations to address deficiencies. Recommendations will be developed for all absent or failed defenses and organizational factors identified.

By using ICAM framework to identify root causes and key contributing factors, the investigation team, employees and organization can feel confident that the recommendations are based on fact, not bias, and when acted upon will lead to continual improvement of safety systems to prevent the reoccurrence of a similar incident.

By Bruce Jamieson, Dept. of Civil Engineering, Dept. of Geoscience, University of Calgary, Calgary AB, Canada
Jürg Schweizer, WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland
Grant Statham, Parks Canada Agency, Banff AB, Canada
Pascal Haegeli, Avisualanche Consulting and Simon Fraser University, Vancouver BC, Canada

ABSTRACT

At the 2004 ISSW, Roger Atkins proposed that—early in the terrain selection process—backcountry travellers could identify which types of avalanches were likely, e.g. wind slab, persistent slab, wet avalanche. These avalanche types are analogous to a set of scenarios in traditional risk analysis. Variations on Atkins’ approach have been incorporated into some public bulletins. The types of avalanches that dominate the danger ratings are called Avalanche Types/Characters/Threats/Concerns/Situations/Problems by different groups. The latest Swiss brochure for recreation in avalanche terrain suggests different observations for the four different types of avalanche situations. To help determine which observations are best for which types of avalanches, a field study was conducted in the winters of 2008-09 and 2009-10 in the Coast Mountains, Columbia Mountains, and Rocky Mountains of western Canada. On each field day, an experienced field team rated the local avalanche danger, identified two dominant avalanche types and observed a standard set of over 20 quick field observations. The quick observations included avalanches, wind transported snow, snowfall, etc. For correlation analysis, we focussed on two distinct classes of avalanche types: 1) persistent slabs, and 2) wind slabs combined with storm slabs. While some observations correlated with the local danger when either class of avalanches dominated the danger rating, other observations correlated best when only one of these two classes dominated the local danger rating. These results may help bulletin writers recommend that recreationists focus on certain local observations for better informed decisions.

INTRODUCTION
For decades, risk analysts for natural hazards have identified distinct scenarios (or potential events) which threaten something of value e.g. property or infrastructure. For each scenario, the probability of the natural event affecting the thing of value and the expected consequences are estimated (Kaplan and Garrick, 1981). Mitigation, if required, typically focuses on the scenarios with the highest risk (combination of probability and consequences). If the probability and consequences for each scenario can be quantified, the risk for the can be graphed as in Figure 1. If either the probability or consequence can only be ranked (not quantified), the scenarios are usually presented in a risk matrix (e.g. Ahrens, 2008, p. 22-24). The scenarios with the highest risk (or unacceptable risk) can be targeted for mitigation. This established approach to risk analysis has been used for long-return period avalanches that can affect property (e.g. Wilhelm, 1998). The same concept is also used informally by guides, forecasters and experienced recreationists, who often focus on one or two types of avalanches (scenarios) when assessing the risk on the terrain being considered for the current day.

For many years some Swiss guides and avalanche educators have proposed asking: “What is the main danger today?” On most days, it can be decided whether it is either a New Snow, and Old Snow, or a Wet Snow situation.

Once the situation is recognized, the mitigation strategy can be adapted (Wassermann and Wicky, 2003). Stephan Harvey has further formalized this approach, called it pattern recognition and added one more situation: Wind Driven Snow, when an increased avalanche danger often prevails (Harvey, 2008).

In parallel with the Swiss development of Avalanche Situations, at the 2004 ISSW in Jackson Hole, Roger Atkins proposed that the probability and consequences be assessed separately for different types of avalanches, e.g. wind slab, persistent slab, wet avalanche, so the decision makers could focus on the one or two scenarios (Avalanche Types) that posed the greatest risk. Some of his avalanche characteristics incorporated terrain, e.g. wind slabs near ridge tops.

Atkins’ concept was used by the Avalanche Danger Scale Project, which was a Canada-US part of the multi-agency project called Avalanche Decision Framework for Amateur Recreationists 2 (ADFAR2). Starting in 2005, the committee of mostly forecasters took a fresh look—actually fresh look after fresh look—at the forecasting process. When they finally had a consensus, the Avalanche Type was a key component of their conceptual forecasting model (Statham et al., 2010). Definitions for the different types of avalanches have been developed. These definitions were the basis for incorporating Avalanche Problems into Canadian avalanche bulletins (Klassen, 2010).

Most recently, Avalanche Type been used as the central theme in a field book for decision-making in avalanche terrain published by the Canadian Avalanche Centre (Klassen et al., 2010). The field book contains templates for recording the relevant observations and facilitates decisions when preparing for and travelling in avalanche terrain.

The concept of Avalanche Type has been and will continue to be applied at various scales. At the slope scale, experienced forecasters and guides can visualize certain types of potential avalanches on the terrain. At the regional scale, some avalanche forecast centres have started to use one, two, or occasionally three Avalanche Types in their public bulletins. Although there is as yet no consistent terminology (Table 1), the concept has caught on and is now used in various applications.

When updating the popular Swiss avalanche awareness brochure “Caution – Avalanches!” the idea of Avalanche Situations was merged with the reduction method with the classical 3x3 framework (Harvey et al., 2009). For each of the four Avalanche Situations, a number of key observations are proposed to help recreationists focus on the most important observations for the day (Table 2).

Early experience with this scheme suggests that on some days it is difficult to distinguish between new snow and wind driven snow. Also, the debate continues about whether to explicitly recommend digging when old snow is the dominant avalanche situation. On the other hand, the emphasis is not on digging when either new snow, wind driven snow or wet snow is the primary avalanche situation.

The relevant observations for each Avalanche Type in Table 2 are based on experience and an understanding of the processes that form the different types of potential avalanches. Haegeli and Atkins (2010) also present key observations from a survey of experienced avalanche professionals. For this study, we set out to use field data (independent of theory or experience) to identify some key observations when different types of avalanches were dominating the danger rating.

METHODS AND DATA
Since the winter of 2007, the Applied Snow and Avalanche Research group at the University of Calgary (ASARC) has been rating the local avalanche danger and making a standard set of over 20 observations (e.g. Jamieson and Haegeli, 2008; Appendix A). Starting in the winter of 2009, we began daily rating the top two Avalanche Types so we could assess which observations were “best” for the various types of expected avalanches. This paper summarizes the results from the winters of 2008-09 and 2009-10.

On most field days in the winters of 2008-09 and 2009-10, ASARC’s field teams in the Coast Range, Columbia Mountains and Rocky Mountains rated the local avalanche danger, made over 20 standard observations (Appendix A), and identified the two most important Avalanche Types (Table 1). For this study we used only the Avalanche Type with the greatest importance—based on its contribution to the danger rating. If the two avalanche types had equal importance (50:50), we used the one recorded as Avalanche Type 1.

Many of the observations were made before and after the decision point, i.e. when the team reached treeline. For each observation, e.g. blowing snow, we used the before or after observation that was more conducive to higher avalanche danger. So, if we observed blowing snow in the morning but not in the afternoon, we used the morning observation.

For most of the observation variables, the specific observation values could be ordered from the least associated with avalanching to the most. For example, the observations for blowing snow were ordered: none, at ridge, below ridge.

Appendix A shows that we rated the local danger for one, two or three elevation zones: below treeline, treeline and alpine. We used the treeline rating, except in four cases in which we did not rate the local avalanche danger at treeline, in which case we used the below treeline rating.

In a few cases in which the precipitation was rain, we treated the precipitation rate as missing. This resulted in the dataset shown in Table 3. Each case is a record of one field team travelling on touring skis in a specific area on a given day.

We excluded Loose Avalanche and Wet Avalanche types from the analysis since there were too few cases. Also because of limited cases, we combined Storm Slab with Wind Slab, and combined Deep Persistent Slab with Persistent Slab.

PRELIMINARY RESULTS
Spearman rank correlations between the local danger rating and the ordered observations are shown in Table 4. Correlations for which p < 0.05 are marked in bold. Correlations for which p < 0.01 are marked in bold italic.

Observations that correlated when either class of Avalanche Type was important?
When either Wind Slab/Storm Slab Avalanches or Deep/Persistent slab avalanches dominated the danger rating, the observations that correlated with the local avalanche danger were: slab avalanches, whumpfs/shooting cracks, clumps of snow falling off trees (tree bombs), deep ski penetration, snow height (snowfall) from in last 24/48 h, and air warming to 0°C (negative) (Table 4). The negative correlation prompted a second look at the data: when the air temperature reached 0°C (usually spring time), the avalanche danger was mostly Low or Moderate.

Observations that correlated when storm snow or wind slabs were important?
In addition to the observations mentioned in the previous paragraph, the snowfall rate, increased hand shear depth and absence of a surface melt-freeze crust correlated with the local avalanche danger when storm snow or wind slabs dominated the danger rating (Table 4). The key variables include the following observations of current or recent snowfall: snowfall rate, accumulated snowfall in the last 24/48 hours, as well as deep ski penetration.

Observations that correlated when deep/persistent slab avalanches were important?
In addition to the observations mentioned for both classes of Avalanche Types, low hand shear resistance, pinwheeling, and snow surface cracking at skis correlated with the local avalanche danger when Deep/Persistent Slab Avalanches dominated the local danger rating.

DISCUSSION
The observations proposed by the Swiss avalanche awareness brochure Caution – Avalanches! (Harvey et al., 2009) and the Canadian Avalanche Centre field book (Klassen et al., 2010) are supported by the correlations in Table 4. For a New Snow Avalanche Situation, recent slab avalanches and new snow amount correlated with the local avalanche danger. For an Old Snow Avalanche Situation, whumpfs correlated with the local avalanche danger. Some correlations, such as the one between pinwheeling and the local danger when Deep/Persistent Slabs are important, are difficult to explain and may not be significant in a larger, more balanced dataset.

For Deep/Persistent Slabs, fewer observations correlated with local danger than for Storm Snow and Wind Slab Avalanches, which is consistent with the greater forecasting challenge for persistent slabs. See also the limited relevant observations in Table 2 for the Old Snow Avalanche Situation.

Research often yields unexpected results. When ASARC’s morning stability evaluation was expanded to include identification of the one or two most important Avalanche Types, one of us (Jamieson) expected the usual response to increased paperwork. Instead, the field staff liked the focus that Avalanche Type provided to the morning safety meeting and has retained it. The Avalanche Type is just one part of the rethinking of the forecasting (Statham et al., 2010) that has become popular with ASARC’s field staff.

SUMMARY
Several regional forecast centres have adopted the concept of Avalanche Character/Type/Threat/Concern/Situation/Problem for use in their public bulletins. This concept is consistent with the scenarios in traditional risk analysis. Harvey (2008) has proposed specific observations for certain classes of Avalanche Situations. For this study, we analysed a dataset of 159 cases (locationdays) in which over 20 observations were made and the local avalanche danger was rated. When the dominant Avalanche Type was either Storm Avalanches or Wind Slabs, the observations that correlated (and were consistent with knowledge of avalanche formation) included recent slab avalanches, snowfall rate, snow clumps falling from trees (usually indicative of wind or warming), deep ski penetration and snow height from the last 24/48 hours. When the dominant Avalanche Type was either Deep Persistent or Persistent Slab, the observations that correlated (and made sense) included recent slab avalanches, whumpfs/shooting cracks, deep ski penetration and increased snow height from the last 24/48 hours.

Further field studies are planned. There are other observations that correlated in this study and may benefit from analysis of a larger dataset. However, any recommended observations should be consistent with the current understanding of the processes that form the different types of avalanches.

ACKNOWLEDGEMENTS
For the careful field work we are grateful to Cam Campbell, Spencer Krkosky, Deanna Andersen, Lydia Marmont, Peter Marshall, Chris Geisler, Ali Haeri, Cameron Ross, Thomas Exner, Mark Kolasinski, Katherine Johnston, Cora Shea, Mike Smith, Dave Tracz and Jordan Stiefvater. Thanks also to Mike Smith for proofreading, to Cameron Ross for checking the data and Dave Gauthier for checking the analysis.

For logistical support for the field studies we thank Mike Wiegele Helicopter Skiing, BC Ministry of Transportation and Infrastructure, BC Ministry of Parks, Parks Canada, the Canadian Avalanche Centre, as well as the Avalanche Control Section of Glacier National Park.

For financial support for the field studies and the first author’s time, we thank the Natural Sciences and Engineering Research Council of Canada, HeliCat Canada, the Canadian Avalanche Association, Mike Wiegele Helicopter Skiing, Teck Mining Company, Canada West Ski Areas Association, the Association of Canadian Mountain Guides, Backcountry Lodges of British Columbia, and the Canadian Ski Guides Association.

REFERENCES
Ahrens, T. 2008. Risk Analysis. John Wiley & Sons, Chichester, England.

Atkins, R. 2004. An avalanche characterization checklist for backcountry travel decisions. Proceedings of the 2004 International Snow Science Workshop in Jackson Hole, Wyoming, USA, 462-468.

Haegeli, P., Atkins, R. 2010. Exploring the ‘It depends’ – How do mountain guides assess avalanche situations? In Osterhuber,

R. and Ferrari, M. (eds.), Proceedings of the 2010 International Snow Science Workshop in Squaw Valley, California, USA, 130-132.

Harvey, S. 2008. Mustererkennung in der Lawinenkunde. In: I. Kroath (Editor), Sicherheit im Bergland. Oesterreichisches Kuratorium für Alpine Sicherheit, Innsbruck, Austria, pp. 88-94.

Harvey, S., Schweizer, J., Rhyner, H., Nigg, P., Hasler, B. 2009. Caution - Avalanches! 6th edition. Avalanche Prevention in Snow Sports, Core team of instructors, Davos, Switzerland.

Jamieson, B., Haegeli, P. 2008. Can field observations be combined systematically with the regional danger rating to estimate the local avalanche danger? Proceedings of the 2008 International Snow Science Workshop in Whistler, BC, 228-237.

Kaplan, S., Garrick, B.J. 1981. On the quantitative definition of risk. Risk Analysis 1(1), 11-21.

Klassen. K. 2010. The Avalanche Hazard Assessment Web-tool – A structured approach to public avalanche forecasting. Presentation at the Spring Conference of the Canadian Avalanche Association, 6-7 May 2010.

Haegeli, P., Atkins, R., Klassen, K. 2010. Decision Making in Avalanche Terrain. Canadian Avalanche Centre, Revelstoke, BC, 62 pp.

Statham, G., Haegeli, P., Birkeland, K., Greene, E., Israelson, C., Tremper, B., Stethem, C., McMahon, B., White, B., Kelly, J. 2010. In Osterhuber, R. and Ferrari, M. (eds.), A conceptual model of avalanche hazard. Proceedings of the 2010 International Snow Science Workshop in Squaw Valley, California, USA, 686.

Wassermann, E., Wicky, E. 2003. Lawinen und Risikomanagement. Edition Filidor, Reichenbach, Switzerland, 60 pp.

Wilhelm, C. 1998. Quantitative risk analysis for evaluation of avalanche protection projects. In Hestnes, E., ed. Proceedings of the Anniversary Conference 25 Years of Snow Avalanche Research, Voss, 12-16 May 1998. Oslo, Norwegian Geotechnical Institute, Publication 203, 288-293

By Paul Cordy

DEPOSIT FROM PATH 19.3 IN KOOTENAY PASS. A SIZE 3 AVALANCHE TRIGGERED BY HELI BOMBING // MOTI

IN THE WORLD OF BIG DATA we have become accustomed to interacting with computer models. The search for good snow inevitably begins by consulting the ensemble weather forecast (the consensus weather prediction of five different detailed models of the atmosphere), just as most searches for knowledge these days begin by consulting Google (a complex and dynamic model of the relevance of digital information). So one might expect that any day now Big Data will begin to spread its tentacles into the world of avalanche safety. But are there particular challenges to using computer models for avalanche prediction? Not the least of these may be thecomplexity of geographic and human factors leading to avalanche formation, and also the scarcity of reliable and continuous information about conditions in the start zones.

So how far have avalanche prediction models come, and how might they benefit organizations and individuals? Will they ever be good enough to rely on in Canada? The British Columbia Ministry of Transportation and Infrastructure (MOTI) has a long history of taking the lead in creating digital tools for avalanche practitioners. These efforts have led to the development of one tool that we know and use already: SnowPro. A lesser-known innovation of the MOTI is the computer-based avalanche forecasting system which began more than 15 years ago in Kootenay Pass. Ted Wieck, former information systems manager for the MOTI avalanche and weather branch, spent over a decade developing the MOTI’s first digital highway, weather, and avalanche database. In the beginning, this meant considerable amounts of tedious data entry for technicians, who would have rather spent more time in the hills and on the road. Ted wanted to make all that data useful to the people who were assiduously collecting it for him, and so he became a fervent supporter of computer-based avalanche prediction.

In the mid-nineties, Dr. David McClung and John Tweedy developed and tested software that used manual weather observations (input by the user, of course) to predict the probability of avalanche activity that day. The prediction was based on a statistical model that was created using historical weather data and avalanche occurrence records from the previous ten seasons at Kootenay Pass. As in all computer models (including Google’s search engine), historic data is used to train the model, or in the case of MOTI, determine the relative importance of various weather variables and how to combine them in a way that computes accurate predictions of avalanches.

This is not too dissimilar to the way that we humans learn. Our experience is combined with training to create mental models of how weather creates avalanches. Often we will compare current weather or snowpack structure with previous seasons’ observations to refine our decisions. The original Kootenay Pass model also retrieved the ten most similar instances of weather and presented the data to the human forecaster to further aid in decision making. In the end, both model approaches were 70-80% accurate. Early in the 2000s, James Floyer proved that similar models could be trained on Bear Pass datasets with similar results.

A CROWN ON PATH 19.8, KOOTENAY PASS // MOTI

As a Masters student with McClung at the University of British Columbia, my contribution to this effort was to dynamically integrate numerical weather forecasts and optimize different versions of the model for each of five different highway corridors with active avalanche control programs. In each place, we used ensemble weather forecasts up to 48 hours ahead into each model, thus extending avalanche predictions into the future (all previous avalanche models predicted present probability of avalanches only). As it happens, predicting avalanches in the future mostly depends on the accuracy of weather forecasting, and most avalanche forecasting models achieve similar accuracy irrespective of the type or complexity of the model.

Of course a 70 to 80% prediction rate is horribly inaccurate given the consequences range from traffic hazard to loss of life, and so there always had to be a human forecaster calling the shots. But before dismissing computer models, one must consider the constraints under which they are working.

 
Take weather forecasting as an analogy. European weather prediction is far better than that of western North America because of differences in density of meteorological stations. Weather systems en route to Europe are being broadcast by countless sensors in myriad islands and land masses in the Atlantic, not to mention by the North American sensor network. Reliable data makes for more reliable weather models. By contrast, weather on its way to western North America passes over the Pacific Data Void, a vast stretch of ocean almost uninterrupted by islands and permanent weather stations. So the very same computer models are often inaccurate more than 24 hours in advance.

So too with computer models of avalanche prediction. Greater complexity and precision of avalanche models is unlikely to improve forecast accuracy until we provide such models with more and better information. The data that we provide prediction models couldn’t possibly compete with the human experience. Avalanche technicians explore the terrain, doing hand shears and listening to the snow settling under their skis. They feel temperature changes when fronts come through, just like the sensor networks do, but sensors can’t see the sun hit certain start zones, and they can’t see how snow is loading up there. Really, it’s a miracle that numerical prediction algorithms are accurate at all.

Therefore, the next goal was to integrate information about the snowpack into the model. The MOTI avalanche models had a built-in mechanism for updating the avalanche probabilities based on new information. Previously, this "prior" information was added by the forecaster in response to avalanche control results or other knowledge that was not available to the model. Prior probabilities could just as easily come from a model of snowpack structure and stability such as the red flag method of SnowPro, or the SNOWPACK physical model used in Switzerland. Unfortunately, changing funding priorities and personnel at the MOTI meant that snowpack information was never integrated into predictions, although it is still used in Kootenay Pass. It’s up to the next generation take it to another level.

NORTH FORK AVALANCHE AREA ON THE EAST SIDE OF KOOTENAY PASS // MOTI

Generational change itself was also a major driver of interest in creating the model. During the latest bout of modeling studies, MOTI was facing the near-simultaneous retirement of all of their technicians. MOTI saw that new staff might get up to speed more quickly if they could scan the results for the size, type and spatial distribution of natural or controlled avalanches in the historical records. The idea was to try to decouple the memories of seasons from the people who observe them, and help bridge the loss of team experience when seasoned professionals retire. Furthermore, the benefits of such systems would be more apparent to successive generations of technicians who would be ever more native to the digital environment. Whereas the old ironsides of the avalanche patch are more likely to decry that their Rite in the Rain books have never crashed nor printed error messages, younger generations are more likely to wish they could just use their iPhone and store it in the cloud.

Computers can supplement our memories, help us see broad patterns, and evaluate the importance of various causal factors that govern avalanche formation. Snowpack depths and precipitation intensity can be measured by satellite, and soon we’ll have satellites sensing atmospheric structure and conditions over the Pacific Data Void. With more and more wired backcountry users and the Canadian Avalanche Centre’s geo-referenced recreationist observation database, avalanche information is set to explode. Models can help us to synthesize an oversupply of data into relevant knowledge. That knowledge will always be limited by the data and model that generate it, and may always require a human to make life and death decisions. However with changing personnel and changing climate, it helps to maintain historical perspective on present events. Avalanche prediction models can help to bridge present and past, and to help us tease out the most relevant information that can be used to manage risk.

As the analytical techniques of Big Data inexorably penetrate all aspects of life, I expect that one day they will be as much a part of the furniture of our lives as smartphones. However, research and development in avalanche risk modeling advances through the vision, passion and forward thinking of people like John Tweedy and Ted Weick, who championed the initiative within the MOTI. Although my main research focus has shifted from avalanche models to pollution modeling and mitigation, I maintain a deep interest in the topic. As we approach the critical information density with respect to snow and weather, I look forward to collaborating with the next generation of visionaries and institutional champions that will bring the avalanche world back in step with Big Data.

By Lisa Dreier

EDITOR'S NOTE: In keeping with the topic of this issue, the intent of this article is to provide insight into technologies less commonly used in North America. In no way does the CAA endorse any particular technology or application mentioned. Lisa Dreier is a representative of Wyssen, which has commercial interest in some of the technologies discussed.

Figure 1: Overview of avalanche detection systems (radar, infrasound and geophones).

SNOW AVALANCHES pose a hazard for people and infrastructure during the winter season. Permanent measures (tunnels, steel structures, etc.) and/or active and passive temporary measures (e.g. road closures, evacuations, preventive avalanche release, avalanche forecasting, etc.) are used to mitigate this hazard. The preventive release of snow avalanches along traffic routes is often used where permanent measures are too expensive or not feasible to construct. Reliable feedback on the success of triggers makes preventive avalanche release more effective as knowledge of occurrence, frequency and size of avalanche events assists personnel responsible for avalanche control and forecasting.

A variety of detection systems are available and have been tested in operational use. Depending on the aim of the operation, the most suitable system should be selected (Table 1).

Table 1: Avalanche detection systems and their suitability for different operations.

RADAR SYSTEMS

Radars have been applied for the detection of avalanches for many years. In most cases Doppler radars are used, emitting electromagnetic waves at a certain frequency, which are then reflected and travel back to the radar (Gauer et al., 2007). Thus the radar requires line-of-sight of the avalanche paths in question. The radar can discriminate between moving and static targets and therefore measures the velocity of the avalanche front.

Experience with Radar
A long-range avalanche radar was installed in Ischgl, Austria in 2011, with the purpose of i) verifying the controlled release of avalanches and ii) gathering information about spontaneous avalanche activity. The radar is a standard operational tool of the safety staff (Steinkogler et al., 2018). The big advantage of the radar is the accurate detection of even small avalanche events. The shorter the distance to the radar antenna and the better the weather conditions (i.e. no rain, no snowfall), the smaller the detectable avalanches are (events of a few 100 m³ in a distance of 1.5 km were detected).

Since radar systems provide data in real-time, alarm thresholds can be defined which allow using the system for the automatic closure of traffic lines. Power can be provided byfuel cells or by permanent power supply if available.

Based on the success of the avalanche radar, the short distance avalanche radar with a 500 m range and less energy consumption was developed (Table 2). They are mounted directly on remote avalanche control systems (RACS) to get immediate information about the success of the avalanche release. This is a much-needed feature for verification of preventively released avalanches. Last winter a short-range radar was installed in Glacier National Park, Canada. The system detected 10 avalanche events triggered by the avalanche tower it was installed on, as well as by the adjacent tower. Other uses of this radar type, such as the detection of persons moving in the area endangered by avalanches, were also successfully tested
(Video: http://gpr.vn/PETRA).

Table 2: Summary and technical characteristics of radar, infrasound and seismic systems.

INFRASOUND
Infrasound waves are low frequency (<20 Hz) sound waves that are not perceived by the human ear. The infrasound technology is widely used for the detection of different natural (e.g. volcanic eruptions) and artificial phenomena (e.g. nuclear explosion). For avalanche monitoring, infrasound technology has significantly improved in recent years in terms of sensor design, noise reduction and processing algorithms (Ulivieri et al., 2011).

Typically, an infrasound detection system consists of a 4 to 5-element infrasound array, with a triangular geometry and an aperture (maximum distance between two elements) of approximately 150 m (Marchetti et al., 2015). During the winter season, the sensors are covered with snow, which helps to dampen ambient noise. This setup allows monitoring of the avalanche activity from all directions within a radius of 3 - 5 km (Table 2).

Experience with Infrasound
To gather information on avalanche activity of a larger area and to assist the local avalanche control team, an infrasound was first installed in 2012 in Ischgl, Austria. The goal was to gather information about avalanche activity from all avalanche paths in the area. Currently, nine systems are used operationally in Switzerland, Norway, Canada and USA (Figure 2). In Canada, an infrasound avalanche detection system has been operated in Glacier National Park for two winter seasons. Last winter the system detected 136 natural avalanches, 137 artillery explosions and 59 controlled avalanches. The detection system notified the forecasters of the onset of natural avalanche cycles and whether artificial avalanche control was successful. This information allowed the forecasters to plan and execute control sessions even more efficiently and thereby reduce closure times of the Trans-Canada Highway.

In Switzerland, Canada, and Norway extensive verification campaigns have been conducted over the last years (Steinkogler et al., 2016). The infrasound system was used to monitor certain avalanche paths which endanger local roads and to define the smallest avalanche size which can be detected. Although the system detected many of the smaller slides (size 1-2), they were not automatically visualized and identified as avalanches as they were below the defined thresholds. Mid-sized and large dry slab avalanches were correctly detected. Additionally, large dry avalanches could be detected up to 14 km away from the system.

Infrasound systems have been deployed in a variety of climatic conditions, ranging from a maritime climate in Norway, to lower elevations and high inner-alpine regions in Switzerland and Canada. At one of the locations, more than two metres of dense (250-300 kg/m3) snow with several ice layers covered the sensors which influenced the quality of the signals. Yet, a generally thick snow cover without ice layers has shown to filter out unwanted frequencies (e.g. traffic noise) and enhance the reliability of the system. Strong ambient noise, such as wind, has shown to complicate the identification of the avalanche signal.

The infrasound system proved to be a very valuable tool for gathering information about avalanche activity of multiple avalanche paths in a larger area. Since it is continuously monitoring it also provides data on spontaneous avalanche activity, which can be very useful information for the local avalanche control team (Figure 2, green arrows).

Figure 2: Example of infrasound detections in Glacier National Park, Canada. The system detects natural avalanches (green), controlled avalanches (red) and detonations of remote avalanche control systems (RACS) or artillery (yellow).

GEOPHONES
Geophones detect the ground vibrations induced by an avalanche in rather close distance to the sensor. So far, the installation of geophones was mainly done very close to the flowing path of the avalanche and the release areas. Avalanches can be reliably detected with approximately 50 m distance to the sensor (Table 2).

Experience with Geophones
Seismic sensors have been applied for operational and research purposes for many years (Perez-Guillen et al., 2016). Figure 3 shows an example where three geophones are deployed in the release area of a high alpine bowl. RACS allow for avalanche control to be performed during day or night and the geophones detect if an avalanche was released.

CONCLUSIONS
From an operational point of view, all systems have reached a technological level at which they work reliably both in terms of system stability and avalanche detection performance (Table 2). All three systems need a calibration period (a few avalanches of typical size for the avalanche path) to optimize the parameters and to be fine-tuned to the local conditions, minimizing false alarms. Generally, an intensive and well-prepared planning phase is essential to achieve the desired functionality and accuracy of the systems.

For authorities operating several avalanche release and detection systems, simplicity is one of the key demands. The integration of all relevant information from RACS and detection systems in one practitioner-friendly and easy to operate platform is crucial. A visualization of the results in a clear, simple way provides a good overview using a mobile phone or laptop (Figure 3).

Experiences with the short-range radar system and infrasound system installed in Glacier National Park, Canada, were recently presented at the CAA spring conference in Penticton by Jim Phillips (Parks Canada) and the author of this article. The presentation can shortly be viewed in the member section of the CAA website.

Figure 3: Integration of remote avalanche control systems (here “Sprengmast”) and geophone and radar (blue areas) detection systems in one user friendly web-platform.

REFERENCES
Gauer, P., Kern, M., Kristensen, K., Lied, K., Rammer, L.,Schreiber, H. 2007. On pulsed Doppler radar measurements of avalanches and their implication to avalanche dynamics, Cold Regions Science and Technology, 50, 55–71

Marchetti E., Ripepe M., Ulivieri G., Kogelnig A. 2015. Infrasound array criteria for automatic detection and front velocity estimation of snow avalanches: towards a real-time early-warning system. Natural Hazards and Earth System Sciences 3(4):2709-2737.

Pérez-Guillén, C., Sovilla, B., E. Suriñach, E., Tapia, M., and Köhler, A. 2016. Deducing avalanche size and flow regimes from seismic measurements, Cold Regions Science and Technology, 121, 25–41, 2016.

Steinkogler, W. , Meier, L., Langeland, S., Wyssen, S. 2016. Avalanche detection system: A state-of-the art overview on selected operational radar and infrasound systems, Interpraevent 2016, Lucerne, Switzerland.

Steinkogler, W., Langeland, S., Vera, C. 2018. Operational avalanche detection systems: Experiences, physical limitations and user needs, 7th Canadian Geohazards Conference, Canmore, Canada.

Ulivieri, G., Marchetti, E., Ripepe, M., Chiambretti, I., De Rosa, G. and Segor, V. 2011. Monitoring snow avalanches in Northwestern Italian Alps using an infrasound array, Cold Regions Science and Technology, Volume 69, Issues 2–3, December 2011, Pages 177–183P.

By Penny Goddard

TREBLE CONE SKI AREA, NEW ZEALAND. THIS BASIN WAS CLOSED DURING THE DAY DUE TO CREEP AND GLIDE CONCERNS. AT 17:00 THE SURFACE WAS STARTING TO REFREEZE, SO THE FORECASTER GAVE THE OK FOR GROOMER OPERATORS TO GO INTO THE BASIN TO WORK. THE AVALANCHE OCCURRED SOME TIME DURING THE NIGHT, FAILING ON DEPTH HOAR AT GROUND. IT DAMAGED THE LIFT BULL WHEEL. // DEAN STAPLES

Avalanches that occur during periods of cooling are important because they can surprise people. The subject first piqued my interest several years ago while watching the sun leave a steep slope on the opposite side of the valley from a ski lodge in New Zealand. When a large slab released from the slope minutes later, it seemed incongruous.

NO OBVIOUS TRIGGER was present: no recent loading by wind, snow or rain, no person and no bomb. The only change I perceived was a rapid drop in temperature as the slope moved from full sunshine to shade and into its associated early evening chill. Days later, the same thing happened on the same slope.

In 2005, I became an avalanche forecaster at Broken River Ski Club in New Zealand. Lingering in the shadows of my mind was an avalanche which had occurred there 13 years prior. The week preceding the avalanche had been stormy, with 142mm of precipitation. Fluctuating freezing levels eventually led to a rain-soaked snowpack. On the day of the avalanche, the weather cleared, temperatures dropped and the snow surface became slick and icy. Staff decided to open the area based on conventional wisdom: cooling and surface re-freezing promote stability.

At lunchtime, a size 4 avalanche failed near the ground on depth hoar, pulling out the entire Broken River basin with a crown up to 2.2m deep. It propagated 800m wide into low-angled terrain, leaving a deposit 20-30m deep. A snow groomer and skiers were in parts of the basin and may have been the trigger, but they were far from the fracture line. Amazingly, because almost all other skiers were inside having lunch only the ski area manager was killed.

A photo of the avalanche hung on the wall in the forecasting office, leaving me chilled and uncertain. Doesn’t an icy, frozen surface mean the snowpack’s locked up? Why did the avalanche fail then and not during the warm storm? Why did it propagate so widely?

So began my investigation. I turned to the books to read up on the phenomenon and learn about the mechanisms behind such events. Beyond some passing references to rapid temperature changes, the standard volley of avalanche reference books left me empty-handed. I tried scientific journals, asked academics and searched online. Very little came to light. So I began to ask my colleagues. A few people had experienced something like
it. Many hadn’t.

A more formal questionnaire followed. In the end, 40 avalanche professionals from around the world responded. The questionnaire focused specifically on ‘re-freeze’ type events (where the snow surface goes from 0°C to below 0°C). I called this a “Cool-Down Avalanche” (CDA). The responses alerted me to the prevalence of surprising, large avalanches during periods of rapid cooling, not just when the snow surface goes from melt to freeze, but also at overall lower temperatures (e.g. a drop from -5°C to -15°C).

This article firstly summarizes the results of the questionnaire, and then highlights a round of cooling-related avalanches in Western Canada during the 2010-11 winter season.

MISTAYA LODGE, WESTERN ROCKIES. OVERNIGHT, JAN. 17/18, 2011 AFTER A STORM WHICH DEPOSITED 1M+ SNOW HAD ENDED. THERE WAS OVERNIGHT AIR TEMPERATURE COOLING FROM -3°C TO -13°C AND WIND (HOWEVER, MANY OF THESE SLOPES WERE NOT LEE TO THE WIND). MORE THAN 20 AVALANCHES RELEASED, SIZE 1 TO 3.5 (MANY 2-2.5) WITH CROWNS 100-150CM, SOME UP TO 200CM DEEP. SEVERAL AVALANCHES WERE OBSERVED IN UNUSUAL LOCATIONS. // DAVE BIRNE

PART 1: THE RESULTS OF THE CDA QUESTIONNAIRE

• In order of descending quantity, observations came from New Zealand, North America, Europe, Asia and Antarctica.
  
• 15 of the 40 respondents had never experienced a CDA. Many more people elected not to answer the questionnaire at all, due to having never experienced a CDA.
  
• About 360 CDA were observed. This number is approximate, as the bulk of observations were poorly recorded, based instead on observers’ memories.
  
• 98% of observed CDA were described as slab avalanches, 2% as loose.
  
• The bulk of the observed avalanches were size 2-3; 14 were size 4 and three were size 5.
  
• 61% were described as ‘glide’ releases.
  
• 20 CDA events occurred within 15-60 minutes of the sun leaving the slope. A further seven occurred less than 15 minutes after the sun left the slope.
  
• 21% of respondents had experienced a close call involving a CDA. These included large avalanches hitting an open highway, burying a ski lift in an area open to staff, and fully burying people in guided groups.
  
• 38% of respondents factor CDA into their decision-making while managing the exposure of people and infrastructure to avalanches. 44% said they do not.
  
• Seven people who had never had a close call involving a CDA factor the possibility of CDA into their decision-making. Interestingly, three people do not factor CDAs into their decision-making, in spite of having had a close call involving a CDA (including involvement in fatal incidents).

The following comments made by respondents help address some of the reasons why CDAs are rarely factored into operational forecasting:

• “[This is] much too speculative a theory to apply in an operational forecast.”
• “I see 'cool-down' as the more stable end of the curve.”
• “I don't factor CDAs into management due to a lack of understanding and observations.”
• “I don't factor CDAs in, as it seems a very rare event.”
• “I don't factor CDAs in, as there’s no knowledge base, therefore they are hard to estimate.”
• “The funny thing is, I probably still guide and operate considering cooling down as a good tick for stability.”

CDA CONCLUSIONS

• CDAs (surface refreezing avalanches) were observed around the world.
• Accidents and near-misses have occurred when operators have re-opened previously closed terrain assuming that cooling means dramatically improved stability.
• Some operators actively manage the CDA hazard through closures or explosives control, which are timed to coincide with rapid cooling or surface refreezing.
• They were rarely observed overall–many experienced practitioners have never experienced a CDA.
• There is a feeling that they are too difficult to predict, so there is a tendency to ignore them when making decisions.

LANARK PATH, ROGERS PASS, 8:00, JAN. 18, 2011. THE AVALANCHE WAS SIZE 4.5 AND DAMAGED TEN ACRES OF FOREST. IT FAILED ON FACETS/CRUST AT GROUND. THE AIR TEMPERATURE DROPPED FROM -3°C TO -17°C OVERNIGHT PRIOR TO THE EVENT. IT FAILED AROUND THE TIME THAT SUN FIRST HIT THE SLOPE. // MINISTRY OF TRANSPORTATION AND INFRASTRUCTURE - AVALANCHE AND WEATHER PROGRAMS

PART 2: COOLING EVENTS IN WESTERN CANADA DURING WINTER 2010-11
It is important to distinguish a key difference between Part 1 and Part 2. The questionnaire in Part 1 asked specifically about ‘re-freeze’ CDA events (snow surface going from 0°C to below 0°C). The events listed in Part 2 occurred during periods of rapid cooling within an overall colder temperature regime and did not involve a clear melt-freeze process at the surface.

The included photos show a succession of large avalanches that occurred during periods of rapid cooling in western Canada. Operators described these events as very surprising, eye-opening, historic and unusual.

SOME COMMON FACTORS IN THE EVENTS OF 2010-11:

• Heavy storm loading occurred prior to the event.
• All but one failed on a persistent weak layer.
• Rapid air temperature cooling occurred, often around 7-10°C
  overnight.
• They were mostly very large events with wide propagation.
• In every case, experienced locals were surprised by the
  events.
  

CONCLUSION

What does all this mean? Is there anything more than a sense of vague paranoia to take away? It seems clear that avalanches sometimes occur during periods of rapid cooling, both when the snow surface is going from melt to freeze and at overall colder temperatures. It is unclear whether, or how, cooling itself triggers avalanches—and that is a topic for a whole different study.

What does seem apparent to me is that many near-misses and possibly some serious accidents were caused by faulty decision-making around cooling. The premise that cooling stabilizes the snowpack after a storm (or solar warming) ends is not always correct. Always basing decision making on this premise can lead to premature exposure to avalanche terrain.

The most constant element in these events was that of surprise. In many cases, professionals were just about to (or just had) opened up terrain previously off-limits for public, guests and staff access.

This research is mostly a collection of anecdotes. In order to really understand the mechanisms behind avalanches that occur during periods of cooling (and from there, to be able to forecast them), as a community we need to better document this type of event. I hope that this preliminary investigation will spark some discussion, spawn some more focussed research and perhaps encourage decision-makers to take a ‘second look’ at conditions during periods of rapid cooling.

I presented this topic at conferences in Penticton, and New Zealand last year. On both occasions, numerous audience members revealed that they, too, had experienced surprising avalanches during times of rapid cooling. My feeling is that this phenomenon, while sporadic, is more common than one might expect.

HILDA PEAK, VALKYR RANGE, JAN. 20, 2011. THIS SIZE 4 AVALANCHE WAS AN ISOLATED EVENT WHICH OCCURRED POST-COOLING. THERE WERE NO OTHER LARGE NATURAL AVALANCHES DURING THE CYCLE. IT DESTROYED MATURE FOREST. // RYAN GLASHEEN

ACKNOWLEDGEMENTS

Thanks to the following for their contribution: Bill Atkinson, Mark Austin-Cheval, Reid Bahnson, BC Ministry of Transportation – Avalanche and Weather Programs, Canadian Avalanche Centre, Peter Bilous, Dave Birnie, Stewart Blennerhassett, Kevin Boekholt, Jay Bristow, Wayne Carran, Howard Conway, Rosco Davies, Jef Desbecker, Thomas Exner, Ryan Glasheen, David Hamre, John Hooker, Andy Hoyle, Damian Jackson, Dan Kennedy, Karl Klassen, Mark Klassen, Brett Kobernik, Gary Kuehn, Chris Landry, John Mletschnig, Jane Morris, Shaun Norman, Tom O’Donnell, Christine Pielmeier, Tarn Pilkington, Nicholas Rapaich, Tim Robertson, Davie Robinson, Mike Rubenstein, Mark Sanderson, Mark Sedon, Ron Simenhois, Jim Spencer, Dean Staples, John Stimberis, Frank Techel, Craig Wilbour and Henry Worsp.

Words and photo By Mike Inniss, MD, DiMM (ICAR)

THE MORE TIME WE SPEND IN THE MOUNTAINS, the more likely we are to find ourselves assisting fellow mountain folk in times of distress. Whether we are responding as organized professionals or because we happen to be in a certain place at a certain time, hopefully we can safely act in an efficient, effective manner to make someone’s bad day a whole lot better. Unfortunately, to err is human nature. This article reviews the most common human factors that interfere with the safe operations of a rescue mission, at times with tragic results.

The mountain environment contains certain inherent elements of risk. At the end of the day we all want to go home to our loved ones in one piece—physically and mentally. A mantra of mountain rescue states that the priority of care is yourself first, your team next, and then your subject. Being mindful of the human factors that can interfere with an operation and potentially lead to an accident helps us to follow that sage advice. By identifying and minimizing the most common human factors that could contribute to a potential chain of negative events during a rescue operation, we can explore ways to lessen their potential impact.

Much of the work in this field comes from within the aviation industry, where the impact of human error can be immediate and drastic. Similarly in the field of medicine, medical error has now been established as a major cause of illness and death. Studies have shown that in Canada more people die from medical error than motor vehicle accidents each year. In the mountain environment, estimates are that upwards of 60 percent and perhaps as high as 80 percent of all accidents during mountain rescue are human error.

SITUATIONAL AWARENESS
At its roots we are all striving to maintain situational awareness and mitigate the human factors that can so easily sabotage it. The ability to maintain situational awareness is a critical and extremely valuable skill required on rescue teams. We have all likely experienced a momentary loss of situational awareness, often during stressful situations, and perhaps suffered consequences as a result. The cost to yourself and/or your team members can be too great in the mountain  environment to allow a lapse to happen. Only with the maintenance of situational awareness can we maintain the critical shared mental model with our teammates that will enhance and ensure successful outcomes.

HUMAN FACTORS IN MOUNTAIN RESCUE
Communication
We are all aware how a frustrating communication breakdown such as lost radio contact can impact a rescue. Miscommunication affects the flow and safety of a rescue mission. Timely, clear and concise communication is a learned skill. The art of closed loop communication (e.g. “heli eta 15 mins” followed by “copy that, heli in 15”) is a skill effective teams practice and promote to reduce communication errors.

The effectiveness of a calm approach to communication cannot be overstated. At times assertiveness may be essential. For example, saying something like "double check that knot; it doesn't look right to me for some reason" could save a life.

Fatigue
It is no surprise to anyone that fatigue as an isolated factor is a common culprit leading to human error during mountain rescue. Professions like pilots, truck drivers and medical residents in training now follow strict guidelines regarding work day length. Many of the world’s most notorious accidents, perhaps most famously Chernobyl, revealed operator fatigue as the major factor when
analyzed. Individual team members must be aware of their fatigue level and teams must have protocols in place to identify and prevent fatigue-related errors.

Stress
Stress has a negative effect on a person’s ability to think and act clearly. Both personal, chronic stress and acute stress in the moment will impact a rescuer’s performance. Fear is also a form of stress and can be severely distracting to the point of immobilization. Physiologically, stress results in the release of stress hormones, most notoriously the avalanche adrenalin, which actually diverts blood away from the brain to the muscles and cardiovascular system. It is challenging to think straight during a fight-or-flight response. The ability to slow things down at critical stressful moments is an invaluable skill. It’s a common tactical adage that “slow is steady, and steady is fast.”

Complacency
“That’s the way we've always done it” is a defining statement and red flag for complacency. Those in the avalanche industry are well aware of the dangers of complacency within a fixed group mindset and the trap of familiarization, both of which are common heuristic traps found when avalanche incidents are analyzed.

Teamwork
Lack of effective teamwork can be a troubling human factor in mountain rescue. Being a good team member takes work and doesn’t necessarily come naturally. Effective communication and the willingness to put the success of the team over personal gain are keys to effective teamwork. There is no role for the individual hero in mountain rescue response. Effective teams make rescue work look downright routine and matter of fact.

Knowledge and Skill
Individuals have to be willing to admit when they may not have the necessary knowledge, experience or skill set to be safe and effective on a rescue mission, no matter how much they may want to help. A rescue mission is no time to test one’s personal limits when an entire team is depending on surefooted, steadfast work. There should be zero tolerance for jumping in over one’s head as the consequences could be too great.

Self-awareness
A healthy dose of self-awareness goes a long way in mountain rescue. It can feel uncomfortable to depend on an overconfident team member who lacks self-awareness about their limits. Blindly pressing on, perhaps even in the face of deteriorating operational or personal factors, is a surprisingly common phenomenon in mountain rescue and reveals how easy it can be to lose situation and self-awareness.

MITIGATING HUMAN FACTORS
Mitigating the human factors that can negatively impact mountain rescue occurs is necessary on both personal and team levels, and should be a continual work in progress during training and throughout a rescue effort. On a personal level, it is necessary to maintain a healthy body and mind. A high level of physical fitness is desirable to reduce the physical stress of mountain rescue work. A clear, positive mindset allows for clarity of thought. And we are becoming more and more aware of the risk of lasting emotional effect of traumatic rescues and how it can interfere with performance.

Regular training and skill maintenance clearly helps team members work as effectively as possible. The development and use of clear operational guidelines and memory aids (e.g., colour-coded ropes, laminated knot cards) can be of great benefit. From a team perspective, communication workshops, rules regarding time on task, and operational debriefs immediately after tasks can all be fruitful exercises when trying to minimize or eliminate human factors that may negatively affect any mountain rescue scenario.

Within the challenging and dynamic mountain environment it will never be possible to completely eliminate individual human factors that could potentially contribute to human error. However, with awareness it is possible for individuals and teams alike to identify these factors, both prior to and during a rescue mission, and to intervene in a timely manner to thereby minimize the impact of those human factors, leading to better outcomes for all involved. After all, someone is already having a bad day and they are counting on you not to have one yourself.

By Rod Gee

Glide slab explosives control results, 50 mile path. Skeena River corridor, west of Terrace, BC. By Rod Gee

My twenty-five year glide slab education began on an early morning in January 1989. A snowplow operator on Highway 16 west of Terrace reported witnessing a Size 3.5 airborne wet avalanche cross the railroad and highway corridors.

The deposit pushed sections of concrete guardrail into the Skeena River. Fortunately, no one was involved. I arrived at the site shortly after hearing the plow operator’s report. “Argh! It’s the glide slab I’ve been monitoring for the last week," I thought; "Why this morning? It’s not raining, and it’s not warm. Why did it run now? Were there indicators I’d missed?”

I came to the north coast of British Columbia to work in CN Rail’s Skeena avalanche program. I brought seven years of work experience in the Rockies, and ITP training in the Selkirk Mountains and the Coast Ranges. However, I had minimal knowledge of glide slab behaviour.

Glide slab prediction is a challenge, compared to the relative predictability of most maritime snowpack avalanche activity. They are classic poster children for the discussion surrounding why “Hazard Level 2” is perhaps a better descriptor than “Stability Good, with the occasional size 4.” Without start zone instrumentation monitoring glide rates, the CN Skeena program offsets uncertainty to some degree with frequent explosives control, and, where effective, runout zone earthworks.

These are some of the observations on formation and natural initiation I now use to evaluate glide slab stability:

• A low-friction ground surface is important for slab formation, but the degree of support from terrain features immediately below the slab is at least as important for slab failure.
• Rapid, early season snowpack accumulation associated with relatively warm air temperatures increases the likelihood of early- and mid-season glide slab formation.
• Lack of an effective ground freeze prior to snowpack accumulation results in increased mid-winter glide rates.
• Rainfall and meltwater percolation in an isothermal starting zone snowpack may accelerate glide rate by decreasing friction at the slab/ground interface. Free water may also decrease the strength of the supporting snow downslope of the glide slab as well as the slab itself. Rain falling into the glide crack above the slab, likely has a similar net effect. However, rain does not
  guarantee slab failure it is only part of the equation.
• Glide slab failure does not require an isothermal snowpack. Failure may occur before the snowpack becomes isothermal or during the overnight cooling phase of the diurnal cycle,
  and without free water being present at the snow/ground interface.

Explosives Initiation
The ideal condition for explosives control occurs when the slab itself maintains a degree of strength greater than that of the snowpack below the toe and along the flanks of the slab. In an ideal scenario, a combination of terrain and weather factors unbalances the downslope snowpack stress/strength relationship to a greater degree than within the slab itself. The toe and flanks
are now barely able to support the loading of the gliding slab. Explosives applied at this time cause slab initiation by triggering a failure of the snowpack at the toe of the slab.

Technicians Herb Bleuer and Mike Zylicz began experimenting with charge quantity and placement in the Skeena corridor in the early 1980s. They realized that conventional charge quantity was usually insufficient for glide slab initiation, and that charge placement was extremely critical.

They also realized that placing the explosives charge into the glide crack above the slab was ineffective because that was not where the stress/strength relationship was deteriorating. Effective
glide slab control is about “kicking the knees out” from under the slab, and not adding load to the slab itself. Their testing produced reasonable results using 100-150kg ANFO charges placed at the toe of the slab.

The best charge placement is a very specific point where the gliding slab is having the greatest effect on the non-gliding downslope snowpack. Current Skeena corridor glide slab control strategy includes the use of charges of 150 and 500kg on 200-500cm deep slabs. Large charges are used because they increase the likelihood of triggering, which reduces hazard at the runout zone transportation corridor and minimizes the likelihood of natural events disrupting rail operations.

That said, control is not always successful. A complex, ever-changing interplay of factors affects glide slab stability, and the puzzle is not completely understood.

Some factors I consider in evaluating explosives control effectiveness include:

• Control is more likely to be successful on glide slabs poorly supported by the terrain below the slab. For example, a poorly-supported glide slab can be initiated with explosives so it will then trigger a better supported glide slab lower in the starting zone that does not respond to explosives.
• Rain or melt-water at the ground/snow interface is not essential for initiation to occur, but it does increase the likelihood.
• Initiating sections of glide slabs is useful both by reducing the deposit volume of a single occurrence, but also because it exposes the ground surface to solar radiation, which then potentially aids in increasing glide rate by introducing more heat into the slab’s basal layers.
• The strength of the snowpack below and alongside the slab allows the slab to glide a significant distance downslope without failing. Increasing glide rate may indicate decreasing snowpack strength.
• A 300-600cm slab can easily glide 50-100m without initiating if the downslope snowpack and terrain accommodates the glide’s loading effect. Increasing glide rate and/or deteriorating strength of the snowpack supporting the slab are two critical initiation factors.
• Three reliable nearby indicator paths I use to assess an east aspect path prone to glide slab formation have a northwest aspect, but the starting zones are at the same elevation. This
  suggests ambient air temperature affects glide slab behaviour to a lesser, but still relevant, degree.

Prediction and control have improved since the 1980s, but we still include a healthy dose of “art” to the “science” of our craft. Explosives control in January 2012 put a size 4 deposit within 2m of the rail roadbed. Is our understanding of glide slab management improving, or were we just lucky on that mission?

Rod Gee is a CAA and AAA Professional member with 30 years industry experience. His association with Chris Stethem and Associates Ltd. from 1985 to 2011 provided participation in a broad variety of Canadian avalanche programs. Rod is owner of Northwest Avalanche Solutions Ltd., and is based in Terrace, B.C.

From Vol. 119, winter 2018-19

By Brian Lazar

THE ASPEN COMMUNITY was rocked April 8, 2018. A long-time and beloved member of the local search and rescue group was killed in an avalanche while skiing recreationally in backcountry terrain adjacent to Aspen Highlands ski area. The entire episode was witnessed by members of the Aspen Highlands Ski Patrol (AHSP) from the ridge and summit patrol shack. It was also captured by a ski area web cam.

The Colorado Avalanche Information Center (CAIC) issued a special product called an Avalanche Warning the morning of the accident. Both the victim and his partner were very experienced backcountry travelers. Both knew the terrain intimately. They witnessed and crossed fresh avalanche debris on adjacent slopes to reach their objective and the site of the accident. The compelling nature of the clues had the snow safety community asking: What happened?

After a summer to reflect on this accident, it’s clear there were several contributing factors and some key take-home lessons that reinforce classic risk management advice in avalanche terrain. Yet it’s hard to escape one critical factor: The two people decided to enter complex avalanche terrain at the tail end of an unusually warm and wet storm.

THE STORM

FIG. 1: NATIONAL CENTERS FOR ENVIRONMENT PREDICTION (NCEP) OF PRECIPITABLE WATER ON APRIL 7, THE DAY PRIOR TO ACCIDENT. THIS SHOWS THE ATMOSPHERIC RIVER OF DEEP PACIFIC MOISTURE HEADING TOWARDS COLORADO(IMAGE COURTESY OF NICK BARLOW)

From April 1 to April 5, conditions were typical of early spring weather in Colorado. There were several centimetres of new snow, and above freezing daytime temperatures with below freezing nighttime temperatures. From April 6 to 8, an atmospheric river funneled deep Pacific moisture into the region (Figure 1). The sounding on April 8 from the National Weather Service in Grand Junction (approximately 150 km west of Aspen) showed the atmosphere had deep moisture to around 300 mb, and precipitable water was over 250% of average for the date. Some portions of the state picked up over 150mm HSTW in the 3-day period.

In the Aspen area, the storm began with above freezing temperatures to around 3600 m, and rain as high as 3400 m. Temperatures cooled as the storm progressed, and snow levels dropped. From April 6 to 7, AHSP measured less than 8cm of dense snow (HN24). On the morning of the accident, April 8, AHSP measured HN24 20cm (38mm). Another 3.8cm of snow fell later that same morning. HST totals were 31cm (43mm).

This was an unusual storm for Colorado, even for spring conditions. It was warmer and wetter than what most avalanche professionals in the area typically encounter. Rain at high elevations at the front end of a storm was rare, as was the high-density new snow that followed. The storm loaded a snowpack typical of the region: thin, cold, and with pronounced persistent weak layers.

FIG. 2: THE ASHP SNOW SAFETY TEAM WAS ALSO CONCERNED ABOUT THEIR IN-BOUNDS TERRAIN. HIGHLAND BOWL, ON THE OPPOSITE SIDE OF THE RIDGE FROM THE ACCIDENT SITE, REMAINED CLOSED ON THE DAY OF THE ACCIDENT.

THE EVENT

The storm cycle had many avalanche professionals on edge. At the CAIC we engaged in discussions both inside and outside our group about the widespread uncertainty. How would the snowpack respond to the rain, storm snow density changes, and rapid HST settlement?

CAIC forecasters issued a High (Level 4) avalanche danger the morning of the accident (Figure 3) and an accompanying Avalanche Warning advising people to stay out of avalanche terrain.

Post-incident interviews revealed that the two skiers involved discussed the unusual storm. The survivor stated that he did not read the avalanche forecast that morning. We don’t know if the victim knew that there was an avalanche warning in effect or if he was aware of the current backcountry avalanche forecast.

FIG. 3: TRIGGERED SLIDES IN MAROON BOWL, 4-8-18. THE GREEN ARROW MARKS A SMALL AVALANCHE TRIGGERED BY AHSP WITH AN EXPLOSIVE CHARGE ON THE MORNING OF APRIL 8. THE BLUE ARROWS MARK LARGER AVALANCHES TRIGGERED BY THIS SMALL ONE. THESE AVALANCHES WERE VISIBLE BEFORE THE TWO SKIERS DESCENDED THE TREES IN THE LEFT OF THE IMAGE. THE YELLOW ARROWS SHOW THE SKIERS’ TRACKS ACROSS AND ALONG THE AVALANCHE DEBRIS. THE GREEN CIRCLE SHOWS THEIR TRANSITION POINT FROM DOWNHILL TO UPHILL MODE. THE RED ARROW MARKS AVALANCHES THAT WERE TRIGGERED BY SKIERS ASCENDING THE SLOPE THAT AFTERNOON, RESULTING IN A FATALITY. (IMAGE COURTESY OF ART BURROWS)

Clues indicating potentially unstable conditions were evident. The skiers observed fresh avalanches before entering the terrain and crossed avalanche debris to get to their intended route. They determined that the fresh avalanches on adjacent slopes were not pertinent, having seen similar avalanches many times on those same slopes in the past. They completed their initial descent without incident. As they skinned up towards their second descent objective, they made an impromptu decision to continue up a slope steeper than 35 degrees with a terrain trap (trees) below them. The survivor stated afterwards that as they climbed, they noted that conditions on that slope felt different than on the slopes travelled up to that point.

As they climbed up for their next run, they triggered a size 2 avalanche. The crown face appeared to be about 40cm deep and 50m wide. The avalanche initiated on a steep, north-facing, near treeline slope and ran up to 150 vertical metres. It swept both skiers down into sparse trees. The victim stopped at a large tree shortly below a rock outcrop. The survivor continued about 60m further, coming to a rest on the snow surface with both skis still attached to his boots.

Despite witnessing the avalanche, professional ski patrollers and search and rescue members made the excruciating decision not to enter the accident site because of exposure and avalanche hazard. They were able to instruct the survivor via radio to self-evacuate down valley and out of harm’s way. The local Sheriff's Office made the decision not to recover the victim that evening or the next day due to lingering avalanche danger.

THE LESSONS
Some of the lessons are too familiar in avalanche accidents, but they do reinforce the basic messaging we promote as avalanche safety professionals:

• The skiers did not discuss the forecast or the warning, and thus did not discuss the advice to stay out of avalanche terrain. How can we improve our outreach to reach all backcountry users?
• They observed fresh avalanche activity on slopes with the same aspect and elevation but did not find this compelling enough to avoid their objective since they had seen those slopes avalanche many times and intended to avoid those particular features.
• They changed their plan on the fly in the field by climbing higher than intended. They traveled safely until they made this change.

A couple lessons are particular to this storm event, and are cautionary for all of us who work and play in avalanche terrain:

• Terrain familiarity can make it difficult to recognize when conditions are different from those previously experienced. This group had used this route before in a variety of conditions. Weather and climate are changing, and we need to be humble in accepting that our methods and evaluations need to be reconsidered. The tried and true approach to risk management can fail.

• Although we could not readily access the crown in our investigation due to lingering hazard, rain at the front end of the storm was likely a contributing factor. We all need to carefully consider rain on snow effects, even those of us who work in historically cold interior climates.

The intent in writing up this case study is not to cast judgment on those involved. Rather, the hope is that an honest reflection will challenge us all to consider what we can do better and to be on guard for storm systems that fall outside past experiences. The times, they are a changin’.

By Colin Zacharias

Conducting an extended column test. Photo by Colin Zacharias

THE WEIGHT OF EVIDENCE
Every winter day we make snowpack observations and extrapolate from observation sites to nearby terrain. Most days, for most avalanche problems, this extrapolation process works and we make key decisions from comparatively few quality bits of information. But it is easy to lose confidence in our abilities when conditions become unfamiliar or our information becomes scarce.

Outside of current avalanching and other alarm signs, and especially during periods of high snowpack variability, experienced observers tend to steer away from drawing quick conclusions from a few snowpack observations. They recognize that one test is just one observation, and to counter possible extrapolation errors they ensure that over the critical timeframe key information is supported and verified.

On the other hand, inexperienced observers may apply too much importance to a persuasive snowpack test result or a single avalanche occurrence and be subject to a confirmation bias. Experienced forecasters, even with a decent amount of information, recognize that at times their best is still in the end just that.

Karl Klassen, Avalanche Canada Public Avalanche Warning Service Manager and mountains guide, recently reminded me with a nice touch of irony that while our data -> information -> knowledge -> wisdom hierarchy (Zeleny 1987) fits into a neat little package, it can also backfire. Depending on the quality and quantity of the data set, its relevancy, and our ability to interpret the info, data isn’t information and information isn’t knowledge, and if one thing is certain, wisdom is a different kettle of fish.

There are times when logistics make it difficult to add weight to the evidence. Poor weather or difficult travel conditions, for example, may prevent access to terrain or study sites. Yet even then assumptions are made and conclusions derived. As Dr. Bruce Jamieson notes in his mountain snowpack presentation for the ITP Level 2 Module 1, “inaccurate assumptions can have serious consequences” when it comes to spatial variability in the mountain snowpack.

Decisions made from a deficit or even partial deficiency of information required to understand the avalanche problem are considered uncertain in light of an applied risk management strategy (as defined by ISO 31000). In the avalanche world we are okay with uncertainty—so long as we know what we don’t know. We understand that as the measure of uncertainty increases so does that long arm of caution when planning to reduce the risk.

In today’s avalanche world in Southern BC and Alberta, professionals rely on a daily information exchange to help manage the complexity of snowpack/terrain variability, to provide a “heads up” early warning system or a nearest neighbor confirmation— “yes, they’re seeing what we’re seeing.” Each day we scan through thousands of bits of data and information on the InfoEx, then go into the field and gather more, aggregate the data into information packets, and analyze and communicate patterns that we refer to as hazard factors.

This article, along with the “How Useful Is the Evidence?” table below, was developed in the fall of 2011 as part of an Avalanche Operations Level 2 Module 3 training course handout to help learners apply the notion of strength and weight to field observations, to use a checklist style verification process, and to encourage quality craftsmanship and a thorough approach when analyzing and discussing snowpack factors. It may help the learner to recognize whether or not their evidence drawn from snowpack tests is helpful to their decisions.

Fig. 1: From CAA Level 2 Module 3 handout

CRAFTSMANSHIP AND CONSISTENCY
“Jeez…. the weather and snowpack vary enough; can’t we all just do the same damn observation the same damn way?”

Regional and operational consistency with technique, application and interpretation ensures the quality of data gathered, recorded and communicated. On professional level avalanche training courses, instructors inform that practice, technique, and a meticulous day-to-day consistency with observations, recording and communication should never be undervalued, nor should the scope of the task be underestimated:

• Ensure that there is an objective for each snowpack test. The early morning safety meeting agenda usually includes assessing the day’s avalanche problem and identifying gaps in knowledge. Know what you’re looking for prior to looking.
  
• Select relevant sites for field test sites using experience and the seasonal observation of how the snow is layered over the terrain. Once sites have proven their worth, they are repeatedly used season to season.
  
• Conduct tests skillfully using standardized, practiced techniques. Observers use established guidelines when conducting, recording, and communicating weather, snowpack and avalanche observations; these come from Observation Guidelines and Recording Standards for Weather, Snowpack and Avalanches (OGRS) and Snow, Weather, and Avalanches: Observation Guidelines for Avalanche Programs in the United States (SWAG).
  
• Ensure consistency within an operation by having employees conduct observations side by side. Discuss technique and compare interpretation during preseason staff training.
  

THE RIGHT TOOL FOR THE RIGHT JOB
The CAA’s OGRS and the AAA’s SWAG provide guidelines for how to conduct and record weather, snowpack, and avalanche observations. Other than a few comments about the observed limitation of certain tests, these guidelines deliberately offer little information on how to apply or interpret the observations as they relate to an avalanche problem or forecast. This knowledge and proficiency is gained through other means, including research articles, professional avalanche training, and on the job training and mentorship.

Of course there isn’t any single test that will reveal exactly what you need to know about snow. Yet every decade or so it seems that guides and forecasters have a new favourite “go to” decision making aid they default to when investigating the current avalanche problem. First it was the Rutschblock test (RB), then the compression test (CT)—or the other way around depending on your region—and now it’s the extended column test (ECT). In a helpful 2010 article “Which Obs for Which Avalanche Type?” Bruce Jamieson and others conducted a field study that did an excellent job of directing attention to those observations that best identify each avalanche concern. The combination of determining the avalanche problem prior to departure (Atkins 2004) and having a good idea about which field observations and tests will best identify the problem is a good start when choosing the right tool for the right problem.

The AIARE Avalanches and Observations Reference included below (published in the AIARE Field Book and instructor materials) was inspired by the aforementioned article and is a useful field reference to help learners target those concerns described in the daily avalanche advisory.

Fig. 2: From AIARE instructor materials and field book, 2012

MANAGING FALSE STABLE AND FALSE UNSTABLE RESULTS
Doug Chabot, forecaster at the Gallatin National Forest Avalanche Center, brings up a good point in a recent blog post: “Snowpit tests are used to show instability, not stability. Never stability. Snow pits (and snowpack tests) do not give the green light to ski; they just give us the red light to not ski. An unstable test result is always critical information. A stable test result does not mean the snow is stable a hundred feet away.”

Chabot’s advice points to the quandary many backcountry recreationists face when analyzing snowpack factors: a test result illustrating unstable snow urges cautious risk reduction, but what does a “no result” mean? Yet estimating where the snow is strong and where the snow is weak is an important skill—particularly for guides committing clients to terrain. Determining stability or the “likelihood that avalanches will not occur” involves a detailed process of gathering evidence, drawing a big picture perspective and not leaping to conclusions from a single observation or test result.

• Knowing the sites that information is coming from, having a systematic or “toolbox approach” to clue gathering (see Fig. 3), and observing the terrain and trends over time are all crucial links in the chain of gathering information and applying it to a hazard analysis. And knowing to what degree those links are missing and then defining the information deficit (whether the uncertainty is weak layer location and distribution, character and sensitivity, or slab characteristic and estimation of destructive potential) is all part of guide and forecaster daily discussion. In addition to the strength, weight and verification checklist provided in Fig. 1, the following points may help when interpreting the day’s investigations.
• A seasonal perspective of where the terrain has historically formed stronger and weaker snow is important. Basal facet development tends to repeat itself in seasonal trends. While near-surface persistent weak layers tend to have a broader distribution, sun or wind effect can result in feature scale variability in weak layer character. For example, DF (decomposed and fragmented snow grain) layers can be unstable locally but may not be problematic on a drainage scale. Expect a higher incident of false stable test results when observing locally unstable layers like DFs, graupel or sun crust/DF interfaces.
  
• One of the best tools for determining the nature of snowpack variability is to simply observe and memorize how the current snow surface or near surface condition changes over the terrain. Knowing the extent of surface hoar, facet, crust, or graupel formation and the distribution of storm snow and wind redistribution of snow helps to form a baseline when later estimating snowpack strength. Imagine yourself a heli ski guide with the opportunity to travel over 10s or 100s of kilometres of terrain on any given day. Using your eyes, your skis, and a few quick penetration and hand tests provides insight into what to expect when the snow surface becomes a buried weak layer. “Quick tests,” while not subject to the same formal research as standard tests, still provide helpful information to an approximate depth of 45cm (Schweizer and Jamieson 2010).
  
• A checklist sum of snowpack structural properties (a.k.a. “yellow flags” or the Snowprofile Checklist (Jamieson and Schweizer 2005)) provide valuable clues about which layer interface is most likely to result in a localized failure/fracture. However, as the checklist sum has a tendency to overestimate instability (false unstable=false alarm), further tests are conducted to determine propensity for propagation (Winkler and Schweitzer 2008). The combination of CTs (with fracture character) and the profile checklist sums provide an excellent tool to determine which layer is worth testing prior to a propagation saw test (PST) or ECT propagation propensity test.
  
• The large column snowpack tests that employ taps or jumps to apply a load to the slab (e.g., the ECT and RB) may still indicate a “no result” when a significant weak layer is buried approximately 1m or deeper—and/or when stiffer snowpack layer characteristics (e.g., a crust) reduce the likelihood that surface taps are affecting the deeper weak layer. The cautionary note is that skier triggering of a layer of this depth may still occur from shallower or weaker area (see case history below). In this scenario, one would not use the ECT or RB as the sole observation tool. It may be more prudent to identify the deeper weak layer with a CT or deep tap test (DT) and if a sudden fracture is observed choose to conduct a PST (or choose a shallower location for an ECT) to observe propensity for crack propagation in the layer. The combination of the small column test (which may err on false unstable but identifies fracture character) combined with a large column test (testing for propagation propensity) both reduces the likelihood of a missed observation and provides more information with a verified result. This “toolbox approach” may help interpret a potential “no result” or a false stable result.

The 2010 Schweizer and Jamieson article “Snowpack Tests for Assessing Snow-Slope Instability” provides an updated, excellent perspective directed at a general audience on snowpack test use and limitations. The following summary points have been paraphrased from the article:

• A good test method should predict stable and unstable scenarios equally well.
  
• Column tests are particularly helpful for assessing persistent slab conditions.
  
• Small column tests (CT and DT test) are useful for identifying weak layers and likelihood of initiation but have a tendency to overestimate instability (false unstable) conditions. Observing fracture character improves, to a degree, the interpretation of the test results. These tests are a better indicator of layer character than instability.
  
• Large column tests are better at predicting propensity for fracture propagation than small column tests, particularly when used in combination with other large column tests. Comparative studies suggest that the RB, ECT, and PST have comparable accuracy.
  
• With large column tests, repeated test results in the same location are useful but the tests repeated on similar, nearby slopes add value.
  
• Each test has a margin of error. Even with very experienced observers an error rate of 5-10% is to be expected. Site selection and interpretation require experience.
  

A TOOLBOX APPROACH TO INVESTIGATING LAYERS OF CONCERN

The Toolbox Approach in Fig. 3 may help students avoid the relatively high number of false predictions that occur due to a combination of several factors, such as extrapolation from single tests and high snowpack variability. The diagram supports a dialogue encouraging students to take a step-by-step approach and observe clues from a combination of tests and observation methods. For example, the combination of both the “yellow flags” checklist sums and fracture character in compression tests provide clues, not confirmation about whether or not a “propagation likely” scenario exists, which is then verified with a large column test that is suitable for testing within limitations posed by the particular snowpack structural properties. Understanding test limitations, matching the test to observed structural properties and verifying observations with complementary tests may improve the ability to interpret the test results and reduce false stable or false unstable predictions. I created this diagram and instructional method five years ago and have included it on the L2M3 and American professional level courses.

FIG. 3 The toolbox approach, ver. 6, Zacharias, 2015 

A CAUTIONARY TALE
Backcountry winter travelers are always encouraged to make weather and snowpack observations in the field, and when possible identify on a drainage and slope scale what the public avalanche advisory describes for the region or range. For the most part, this is an effective risk management strategy. However, there have been a number of close calls, incidents and avalanche accidents with backcountry users increase their risk by not managing exposure when gathering information or misinterpreting the observations they collect. In December 2007, a fatal avalanche accident occurred on Tent Ridge in Kananaskis Country when two backcountry skiers were killed conducting a snow profile in the start zone of an avalanche path. Older examples of riders conducting tests on or very near the slope and being subsequently killed include Wawa Bowl, AB, and Mt. Neptune, BC in 1984, Thunder River, BC in 1987, and White Creek, BC in 1993. More recent incidents include Ningunsaw Pass, BC in 1999 and in Twin Lakes, CO in 2014, where a group of seven dug a profile and conducted eight CTs on a slope before choosing to ski it (see CAIC Incident Report for more information).

There are also several examples of “close calls” where test results gathered and extrapolated to chosen terrain illustrated one problem but not the primary concern. A recent example occurred in December 2013 in Hope Creek, BC involving two backcountry skiers. This is an unfortunate example where a combination of well-intentioned observations formulated a confirmation bias and decision making trap. The rider’s observations prior to descending the slope included three existing ski tracks on the slope, 15cm recent snow, light winds, -3°C and no recent avalanches. The group conducted several tests with the following results: CTM16 (SC), ECTP 23, and “numerous ski cuts in the start zone,” all revealing a significant surface hoar layer (size 7-10mm) 40cm deep but nothing deeper. A DT also revealed no results on deeper layers. The group decided that the surface hoar layer was manageable and to ski the slope one at a time. Rider 1 skied the slope with no problems and stopped 400m below, adjacent to the path trim line. Unfortunately, Rider 2 triggered the slope after landing an air low down in the start zone. The resulting D3 avalanche fractured 100m wide on basal facets 80-120cm deep and well below the surface hoar layer. The fast moving avalanche debris caught Rider 1 on the path’s edge before he could scramble to safety. Both involved were carried approximately 700m downslope. Both were buried and badly injured but were able to self extricate, call for help, and were successfully rescued
(Editor’s Note: read a first-hand account of this avalanche by Billy Neilson in The Avalanche Journal Volume 106).

Those involved generously provided the CAA occurrence report with snowpack observations and insight into what gave them confidence to venture onto this particular slope. This event is a helpful wake-up call as we can all place ourselves in their decision making shoes. In hindsight, it is revealing to examine the Kicking Horse Mountain Resort local forecaster’s public video statement issued on Vimeo on December 13, 2013 for the nearby backcountry terrain. The forecaster warned there is a “basal weakness at the bottom of the snowpack that is still reactive,” and “skier triggered size 3 avalanches have occurred,” and “avalanches had triggered larger slopes sympathetically,” and that “now is the time to be very mindful of slope history.” He went on to emphasize “without that degree of confidence that an avalanche has happened [on your slope of interest], you are really rolling the dice hopping onto big terrain.” This incident—though occurring over one week after the video statement—illustrates that when it comes to managing deeper persistent slabs, the careful observations and good well-learned techniques of the backcountry travelers were not sufficient to protect them from the lingering hazard. It also reveals the big-picture perspective of the forecaster, who clearly warned of the more serious basal concern.

Experience with this type of problem, experience monitoring unstable snow in a shallower snow climate, experience matching specific tests to specific problems, and experience managing false stable results and prioritizing the key concerns are all factors that may have given the experienced forecaster a different perspective than the backcountry riders. In this case, the knowledge of how the snowpack lay over the terrain held more weight than even a series of test results, all of which drew attention to a secondary problem that, while significant, was less so than what lurked below.
The bottom line is snowpack tests used to predict instability, while valuable when employed appropriately, are not foolproof. As Schweizer and Jamieson state obviously and importantly in the aforementioned 2010 article, “decisions about traveling in terrain should not be based solely on stability (snowpack) test results.”

REFERENCES
American Avalanche Association and USDA Forest Service National Avalanche Center. 2010. Snow, Weather and Avalanches: Observation Guidelines for Avalanche Programs in the United States. 2010. Pasoga Springs, CO: AAA. http://www.avalanche.org/research/guidelines/pdf/Introduction.pdf

Atkins, Roger. 2004. “An Avalanche Characterization Checklist for Backcountry Travel Decisions." Proceedings of the 2004 International Snow Science Workshop. Jackson Hole, WY. http://arc.lib.montana.edu/snow-science/objects/issw-2004-462-468.pdf.

Avalanche Canada Incident Report Database. Golden, Hope Creek Draining, Privateer Mountain. December 29, 2013. http://old.avalanche.ca/cac/library/incident-reportdatabase/view.

Campbell, Cam. 2008. “Testing for Initiation and Propagation Propensity.” Canadian Avalanche Association Level 2 Module 3 Lecture.

Canadian Avalanche Association. 2014. Observation Guidelines and Recording Standards for Weather, Snowpack and Avalanches. Revelstoke: CAA. www.avalancheassociation.ca/resource/resmgr/Standards_Docs/OGRS2014web.pdf

Chabot, Doug. “Another viewpoint on a Backcountry Magazine article.” Gallatin National Forest Avalanche Center Blog, November 6, 2015. http://www.mtavalanche.com/blog/another-viewpoint-backcountry-magazine-article

Colorado Avalanche Information Center. Colorado, Star Mountain. February 15, 2015. https://avalanche.state.co.us/caic/acc/acc_report.php?acc_id=526&accfm=inv

Gauthier, Dave, Cameron Ross, and Bruce Jamieson. 2008. “How To: The Propagation Saw Test.” University of Calgary Applied Snow and Avalanche Research. October 2008. http://www.ucalgary.ca/asarc/files/asarc/PstHowTo_Ross_Oct08.pdf.

Jamieson, Bruce. 2009. “Mountain Snowpack and Spatial Variability.” Canadian Avalanche Association Level 2 Module 1 Lecture.

Jamieson, Bruce. 2003. “Risk Management for the Spatial Variable Snowpack.” Avalanche News 66 (Fall 2003): 30-31.

Jamieson, Bruce and Jürg Schweizer. 2005. “Using a Checklist to Assess Manual Snow Profiles.”
Avalanche News 72 (Spring 2005): 57-61.

Jamieson, Bruce and Torsten Geldsetzer. 1996. Avalanche Accidents in Canada Volume 4: 1984-1996. Revelstoke: Canadian Avalanche Association.

Jamieson, Bruce, Jürg Schweizer, Grant Statham and Pascal Haegeli. 2010. “Which Obs for Which Avalanche Type?” Proceedings of the 2010 International Snow Science Workshop. Squaw Valley, CA. http://arc.lib.montana.edu/snowscience/objects/ISSW_O-029.pdf

Klassen, Karl. 2002. American Institute for Avalanche Research and Education Level 2 Student Manual. 2002 Version.

Ross, Cameron, and Bruce Jamieson. 2008. “Comparing Fracture Propagation Tests and Relating Test Results to Snowpack Characteristics.” Proceedings of the 2008 International Snow Science Workshop. Whistler, BC. http://arc.lib.montana.edu/snow-science/objects/P__8177.pdf.

Schweizer, Jürg and J. Bruce Jamieson. 2010. “Snowpack Tests for Assessing Snow-Slope
Instability.” Annals of Glaciology 51(54): 187-194.

Simenhois, Ron and Karl Birkeland. 2007. “An update on the Extended Column Test: New Recording Standards and Additional Data Analyses.” The Avalanche Review 26(2).

Zeleny, Milan. 1987. “‘Management Support Systems: Towards Integrated Knowledge Management.” Human Systems Management 7: 59–70.

“Skiers Died Testing for Avalanche.” The Calgary Herald, December 11, 2007. Accessed December 10, 2015. http://www.canada.com/story.html?id=75d72a3c-c743-4c65-a0c2-a18728813217.

By Steve Brushey

Photo: Because the site was only accessible by helicopter, Quantum Helicopters in Terrace was contracted, providing daily access to the site and slinging of all materials, requiring a total of 75 hours of flying. By Steve Brushey.

APPROXIMATELY 80% OF HIGHWAY avalanche road closures along Highway 16W occur in the 35 Mile avalanche area, located 56.4km west of Terrace. Compounding the problem is restrictive narrow lane width, due to a CN rail track on the south side of the highway and the 35 Mile rock bluff on the north side. Poor sight lines, and lack of a ditch and snow storage add to the 35 Mile problem. This area is also prone to ice fall, resulting in motor vehicle accidents and numerous near misses. Currently the avalanche hazard at 35 Mile is managed through preventative closures and avalanche control, which fall under the Ministry of Transportation and Infrastructure Avalanche Safety Plan. The ice fall hazard remains the responsibility of the maintenance contractor and is mitigated using a high powered rifle with limited success.

During the winter of 2012-13, an increase in ice fall garnered the attention of Ministry representatives. A consultant was hired to find a solution to both the ice fall and avalanche hazard. Thurber Engineering and Dynamic Avalanche Consulting were retained to provide ice fall solutions, rock structure mapping and avalanche fencing design.

The Thurber/Dynamic report’s scope only considered avalanche fencing structures. The study did not include avalanche control products, as the Ministry of Transportation Avalanche and Weather Program preferred a longer term, more permanent solution that would eliminate the need to do control work at the East Bluffs, significantly reduce or eliminate avalanche hazard forecasting, and provide a cost effective solution. Of interest, McElhanney Engineering was retained by a regional project management team, which looked at several high level solutions which included rock cuts, tunnel, causeway and snow shed options. Costs ranged from $37 million to $140 million. Other than the snow shed option, avalanche snow fencing would be required for all of the other options. Avalanche snow fencing made the most sense economically in both the short and long term, given the scope of the initial project.

The MoT Northwest Avalanche Program was concerned about the potential for the snow fences to increase the amount of melt water through melt-freeze cycles, leading to a possible increase in ice fall. In order to further study the potential problem, the Mid-Chutes section of 35 Mile was selected for a trial fencing project. If meltwater or ice fall increased, the likelihood of falling ice impacting the highway would be negligible due to terrain configuration at the Mid-Chutes. In addition, the avalanche hazard at the Mid-Chutes would be mitigated.

During the early spring of 2013, the Northwest Avalanche Program gathered the necessary permits required to proceed with the project. These included archeological and environmental assessments, and a permit to construct a helicopter pad in advance of any required work. During this time, Thurber/Dynamic made site visits to the area to gather information and data required to complete their initial report. This report was finalized in August 2013.

Due to various delays, in the fall of 2013 the project was postponed until 2014. In December 2013, 81.7m of 3.0Dk GeoBrugg Spider Avalanche Fencing arrived in Terrace and was stored for the winter.

In the spring of 2014, the Northwest Avalanche Program began administrating a contract for the installation of the fencing at the Mid-Chutes. Retaining an Engineer of Record for the project did prove to be a challenge, however once finalized, the planning and design of the installation began. This took longer than anticipated. Due to the overall cost estimate, the project now qualified as a Major Works Project and was advertised on BC Bid for qualified installers. The contract closed in early September and the contract was awarded to Pacific Blasting and Demolition of Burnaby, BC. Installation began on September 26 and was completed November 4, 2014.

The installation consisted of several phases involving site preparation and danger tree removal, fence and anchor layout, anchor drilling and grouting, anchor testing, and fence installation. During this time, technical support was provided by Geobrugg, Dynamic Avalanche Consulting and Thurber Engineering. Because the site was only accessible by helicopter, Quantum Helicopters in Terrace was contracted, providing daily access to the site and slinging of all materials, requiring a total of 75 hours of flying. A gravel pit close to the work site was used for the daily mobilization of crew and materials.

Traffic control was required throughout the duration of the project, requiring delays of up to 20 minutes to ensure public safety while Pacific Blasting and Demolition crews performed their work 350m above the highway. During the initial phase of danger tree removal, several track occupancy permits were required from CN Rail in order to safeguard the rail right of way.

Despite a very wet fall, the project was delayed for only three days when crews could not work. This proved testament to the hardy nature of the installation crew and the expert flying of Quantum Helicopter pilots.

Photo: Pacific blasting and demolition crews perform their work

350 metres above the highway. By Steve Brushey.

With the trial phase fencing installation now complete, the fencing will be monitored throughout the winter of 2014-15 to determine the feasibility of the next phase of avalanche fencing for the East Bluff area. The East Bluff phase requires approximately 400m of fencing to complete the main avalanche area. Once complete, the final phase of ice fall hazard mitigation will follow, requiring an ice retaining structure and drape nets. A short, low elevation rock cut is also a possibility.

Moving ahead, the East Bluff start zones of 35 Mile avalanche area face environmental challenges which include nesting birds, bats and goat kidding areas. In addition, archaeological points of interest need to be preserved. The size of the area will also require the construction of another helicopter pad and many more track occupancy permits from CN Rail. An early analysis suggests the work can be completed over two months which if undertaken during the summer months with longer days and technically better weather, should promote efficiencies and cost savings.

By Troy Leahey

The start zone. Photo by Jim Bay.

This case study details a skier-triggered avalanche that occurred in the backcountry accessed from Revelstoke Mountain Resort (RMR) on February 22, 2013. The party included five young men, all new to Revelstoke. Three members of the party were involved in the avalanche. Two of these were partially buried; the deceased (an RMR staff member) was fully buried despite wearing an airbag. It was a size 2 slab avalanche with an approximately 40cm fracture line, which failed on an early February surface hoar layer.

Analyzing accidents has long been an important part of the CAA ITP program and in other risk  reduction industries. It is easy to be the armchair quarterback after an incident and identify the mistakes people made, but I believe it is also important to identify what was done well in the rescue effort to use as a good learning tool.

My involvement in this accident was on a number of different levels. As a member of Revelstoke Search and Rescue, I assisted Buck Corrigan and Ryan Buhler with the body recovery the day after the accident. I watched and helped interpret a Contour headcam video worn by one of the rescuers during the rescue effort for local members of the RCMP and a representative of the BC Coroners Service. This was a sobering but interesting piece of footage; although the actions of those involved on the scene would be apparent to most readers, the footage required some explanation and interpretation for non-skiing investigators. I interviewed some surviving members of the group for clarification on the location of those involved and their actions for the Coroners Service.

I also led a debrief at RMR for friends and co-workers of the deceased, including the other young men involved in the accident. This debrief was the most challenging public speaking exercise I have ever undertaken. Our company president asked if I could speak about the accident, as staff members and friends in the community had unanswered questions, and answers can help lead to understanding and closure. I wanted to be quite frank about the obvious mistakes made, as they were an opportunity for learning. I also wanted to commend the survivors on their effort and help them recover some confidence and dignity. I focused on the following points in the debrief.

This photo shows the position of the skiers when the avalanche occurred and where they ended up. Their uptrack is in red, the avalanche is outlined in black, and the blue dot is where the victim ended up. Photo by Troy Leahey.

MISTAKES:
• The most obvious mistake was the aggressive terrain choice—the danger rating at alpine and treeline was high. The five males were young, aggressive skiers with limited backcountry experience. This is the demographic we may expect to see on the avalanche fatality list. The deceased had skied in the terrain the day before and felt confident in his decision to lead the rest of the group to that zone. He had spent many days in this area in what had been a mostly stable season to that point. It was also the first major surface hoar cycle we had experienced in the season, and this type of avalanche failure may not have been familiar to a young German in Canada for his first winter. The CAC’s avalanche forecast was bang on—as it usually is—but youth, overconfidence and a desire to ski steep powder caused this glaring information to be ignored.

• Poor group management. The first three skiers on the uptrack were all involved in the avalanche; they were obviously not well spaced out enough and were all engulfed by the slab. Luckily the last two in the group were slower and not affected by the slab failure, and were able to execute a fairly quick rescue. Complacency on uptracks is a common problem for less experienced backcountry travellers. The group of five had been split into the first group of three up front and the slower pair at the back, which leads to a lack of communication and no consensus in the go or no-go decision. The most educated member of the group had been a student of mine on a CAA Avalanche Operations Level 1 course the previous year in Whistler. I spent a lot of time speaking with him about their decisions that day. He admitted to having reservations about the decisions being made, but did not speak up and deferred to the deceased as the leader, since he was most familiar with the terrain.

• Improper use of an avalanche balloon pack. Wear the crotch strap if you are wearing an airbag. The deceased was near the surface with his airbag inflated and clearly visible from 100m away. He had not attached the crotch strap of his airbag. As the overburden of the slab he triggered from mid-slope overran his position in the toe of the debris, the airbag was lifted away from his back and above his head. This caused two serious problems. As the balloons and pack were pushed forward and downhill it lifted the pack, causing the chest strap to catch on his chin and impede his airway. Secondly, the buoyant airbag also pulled the victim’s arms above his head, restricting movement and the ability to use hands to clear his own airway. The Contour video showed quite clearly the victim’s lifeless arms well above his head. The space between the balloon pack and the victim’s back was approximately 40-50cm.

The avalanche path where the victim was caught is on the right. Photo by Jim Bay.

WHAT THE RESCUERS DID WELL:

• The two not involved took a safe route to the toe of the debris and did not expose themselves to any additional hazard. They quickly and efficiently went into rescue mode when they saw the airbag on the surface, and began the excavation by first removing the pack and digging to the head to clear the airway.

• The two partial burials ended up mid-path and were able to self-rescue and do a transceiver search of the slide path down to the victim.

• Group members performed good first aid on the victim. Once they uncovered his head, they immediately cleared an ice chunk from his mouth and pulled him out to a prone position where they started CPR. Considering the environment, they performed excellent CPR with quality air movement as exhibited by the face of the victim in the video.

• The survivor with the most training took control of the rescue effort. He dispatched one of the members of the party to start moving back to the ski area boundary to report the accident as there was no cellular reception on the accident scene. This individual really led the first aid efforts as well.

• After at least a half hour of CPR, they made the decision to try to move the body with an improvised toboggan. They did not get very far as the conditions were very deep, but were able to move the body to a safe location out of the avalanche path. They then made the very difficult decision to leave the body and return to the ski area, as the weather conditions were deteriorating quickly. They left the body in a seated position under a tree with the inflated airbag and flagging tape arranged to mark its position, making our recovery very easy the next morning.

This was an unfortunate accident involving a group of nice young people from around the world enjoying the mountains in Revelstoke. There is nothing ground breaking about this accident other than the question of whether the airbag crotch strap could have made a difference. So why did I write this for The Avalanche Journal on a 30° July day when I’d rather be fishing? On a personal level, it brings back a bunch of vivid images and unpleasant emotions that make me sad. However, on the big-picture level this is an opportunity for others to learn and avoid mistakes in the future. A case study is really a story; this story may be repeated in Whistler, Banff or beyond. Hopefully the mistakes made and the triumphs that occurred in this accident will resonate and help others make better decisions in the mountains. That makes me happy.

Have a fun, safe winter.

By Roger Atkins

From vol. 120, spring 2019

I first wrote about Strategic Mindset in an appendix to my CAA Level 3 project. Some years later I presented strategic mindset in Banff at ISSW 2014 in a paper entitled “Yin, Yang, and You.” I am surprised by the amount of interest these papers received from professional guides, but also among people doing other types of avalanche safety work. Some guiding operations chose to formally incorporate strategic mindset into their meetings; this is now common practice in North America and elsewhere. The strategic mindset idea originated in the context of guided helicopter skiing, but the concept can be adapted to other endeavours.

During a helicopter skiing operation’s morning meeting, the guides discuss and assess hazards and other considerations for the coming day and produce a ‘run list’ - a binding agreement that excludes some runs from consideration for the day and identifies which other runs are open for guiding. The run list is only the first level of the day’s decisions; many hazards remain on open terrain and actual travel and risk treatment decisions continue throughout the day. I noticed that I automatically take something less tangible than the run list but equally important away from the meeting, something that strongly influences my remaining decisions. I recognize this as a mindset: a personal perspective on the day. This perspective (or filter) makes me wary of certain terrain characteristics. It also establishes a desire for select rewards to seek and attracts me to terrain that offers those experiences.

“When we change our mindset, we actually change the way we
see the world.” - Shelly Carson, Harvard Brain Researcher

 
As implied by the following definition, a mindset results in an inclination that influences decisions, but it should not be considered a recipe for making decisions.

MINDSET:
1. A fixed mental attitude or disposition that predetermines
a person's responses to and interpretations of situations.
2. An inclination or a habit.
(The American Heritage Dictionary, 2009)

Although strongly related to the discussion around hazard assessment, I also noticed how my mindset is influenced by other factors. Some are personal, such as fatigue or desire; some are operational, such as terrain maintenance through skier traffic. Over time I identified that certain situations repeatedly led to familiar mindsets. It occurred to me that perhaps there is value in identifying familiar situations and in strategically adopting a corresponding mindset.

Guiding operations do not willingly add anything without value to their daily routine, so what does strategic mindset provide that was not there before? One standout benefit is that strategic mindset is a communication tool. The language of strategic mindset can help guides express how they feel about the approach to the day. We have always informally shared our feelings but adding strategic mindset to the meeting agenda makes this more consistent. During the day, it also provides a clear and concise way to communicate if our mindset is changing or if our actions seem inconsistent with the mindset. This communication can help us work better together as a team. Strategic mindset is also useful for communication between operations. Some guides use strategic mindset to communicate with their guests.

Strategic mindset is a deliberate biasing strategy. Although it is typically reflected in the daily run list, I find that my mindset is most relevant to on-the-spot guiding decisions during the day. When approaching a potentially critical terrain feature, we must decide whether to avoid it, to stop and manage the risk, or to just ski right over it. This happens tens of times per day and we are quickly overwhelmed by a detailed analysis of every decision; strategic mindset can simplify many of these decisions. Choices that fit the mindset often require relatively little effort while choices that are out of character with the mindset demand more careful assessment.

Decisions in avalanche terrain are high consequence risk vs reward decisions that are made under uncertainty. Traditional methods and education tend to focus on the hazards and associated risks and completely ignore the reward part, but the potential rewards are the only reason we even accept any risk. We cannot account for our humanity without considering the rewards. Even at the best of times, our written assessments tend to read like a horror show, only identifying hazards and not speaking to positive aspects that enable us to satisfy our desires without unacceptable risk. Strategic mindset is more balanced in that it includes the idea of adjusting one’s desires to fit the situation. Some familiar mindsets bias us toward actions that keep us safe in difficult times while other mindsets enable us to capture our dreams when the opportunity arises.

We are naturally biased toward actions that fulfill our desires. Part of strategic mindset is to adjust our desires to fit the situation, thus creating a motivational bias toward actions that fit the situation. One of my fellow guides summarized a past close call nicely:

“It was a stupid idea...I mean, it was a good idea, but it was the wrong day.”

There are potential downsides to the operational use of strategic mindset. Strategic mindset is a deliberate bias. An appropriate bias is beneficial, but what if we get it wrong? Interestingly, when we make the wrong choice of mindset, I find that it is usually easier to recognize the mistake, change our mindset, communicate the change and adjust our decisions than to re-analyze the hazard assessment and adjust accordingly. Maybe this is because the mindset manifests itself as a feeling rather than the conclusion of an analysis. Nevertheless, it is critical to keep open eyes and an open mind to combat confirmation bias, both for hazard assessment and strategic mindset.

My original list of familiar mindsets is not intended to cover all situations and it can be an undesirable distraction to try to select the right choice from such a list. As implemented at CMH, we are not forced to choose a mindset. We can leave it undetermined or coin a phrase that captures a new strategic mindset, for example High Alert or Spring Transitional. Worthy additions that are concise and self-explanatory will persist; others will naturally die. I encourage expanding the list of familiar mindsets and adapting it to suit your needs. Allow the language of strategic mindset to evolve.

The use of strategic mindset is not a substitute for diligent observation and assessment. Strategic mindset is intentional manipulation of human behaviour to our benefit. It is intended to work in conjunction with a solid foundation based on the fundamentals of avalanche hazard assessment.

Photo by Wren McElroy

This article was originally published in the Spring 2019 issue of The Avalanche Journal

By Walter Bruns

From vol. 120, spring 2019

Kobi Wyss was CMH Guiding Operations Manager back around 1990. He came to me one day and said (almost a direct quote – something like): “Hey, there’s this guide from Utah who wants to work here. He’s a physicist and really good with computer stuff. Even built a database for snow observations. Do you think we should hire him?”

The name Roger Atkins was familiar. His work in the avalanche patch was already well recognized. His experience at Wasatch Powderbird Guides was extensive. I replied on the spot: “If we can get a work permit, HIRE HIM!”

So this soft-spoken, somewhat shy, square-jawed, broad-shouldered guy shows up in Banff. There was a lively intensity and unbounded intellectual curiosity about him. He went to work in BC. He brought his computer with his guiding gear. He loved all things Canadian. He made a career and a home here.

“Snowbase” evolved dramatically over some 30 years. Roger built on his original concept, adapting it continuously to the needs of a complex operation. He did a lot of this work while guiding full shifts, in his spare time, or on his own time. He collaborated closely with CMH Snow Safety Director Colani Bezzola. Oh to be a fly on the wall in the room where Roger and Colani were debating their (rather strongly held and often quite distinct) views on what the software could do, should do, would do, or not; depending!

Roger’s creation grew out of the environment that he grew into. He’ll be the first to acknowledge the influence and contributions of so many of his colleagues and peers. Snowbase was truly ground-breaking work, showing the way for development of related systems such as the CAA’s InfoEx and Avalanche Canada’s public interfaces.

But lively intensity and unbounded intellectual curiosity do not rest. Roger still guides at Galena. As Werner Munter once observed: “My god, you people LIVE IN THE SNOW!” Yes, when you dig steps down to your front door, or wallow to the study plot, and spend most days out in the mountains, you very much become a product of your environment.

Roger looked into the minds of the guides he worked with, and he looked within himself. He saw patterns of attitude, belief and behaviour emerge. Ever the physicist, he identified, categorized and sought functional relationships. He implemented ideas and tested them with the team. He has given us the concept of “Strategic Mindset.”

What we do with it is up to us.