Avalanche Accidents

General Analysis of Trends and Factors Causing Avalanches

The information in this section is a general analysis of trends and factors causing avalanches, based on investigations into reports of serious avalanche incidents. Backcountry users are strongly encouraged to report all avalanche incidents, including “near misses” and incidents that do not cause serious injury. To report an incident, click here.

Reporting of avalanche incidents is important because it:

  • Allows the CAC to warn others about unexpected conditions through the Public Avalanche Bulletin and the online public discussion forum
  • Supports incident prevention programs of the CAC, national parks and other agencies
  • Supports the maintenance of search and rescue teams
  • Focuses avalanche research on practical problems faced by recreationists

More in-depth analysis of the avalanche incident information presented here can be found in the book, Avalanche Accidents in Canada Volume 4: 1984 - 1996, by Bruce Jamieson and Torsten Geldsetzer. Hardcopies are available at the Canadian Avalanche Centre, bookstores and from the CAC’s online store.

General Victim Profile
There are approximately 150 avalanche fatalities reported every year by the 17 countries that are members of the International Commission for Alpine Rescue (ICAR). In the past 30 years, from 1978 to 2007, an average of 11 avalanche fatalities have occurred per year in Canada. This has increased to an average of 14 avalanche fatalities per year in the ten year period, from 1998 to 2007.

There is a definite trend in Canadian avalanche incidents in terms of fatalities, gender, location and other factors. The statistics reported here are taken from an analysis performed on the fatality dataset taken between 1984 and 2003. From the perspective of 2010 this information already seems dated and we are working on updating these statistics. One thing we know for certain is that snowmobiling is now the backcountry activity that resultsu in most avalanche fatalities. However, between 1984 and 2003, the profile of a typical avalanche victim and the circumstances during which the incident occured included:

  • A male in his 20's
  • A backcountry skier
  • With a 73% chance of being killed during the months of January, February and March, compared to 23% during November, December and April
  • Between the hours of 12:00 noon and 2:00 pm
  • Triggering an avalanche while on foot (55%) or snowmobile (32%)

Between 1984 and 2003, almost half of the avalanche incidents in Canada occurred in the interior ranges of British Columbia due to more intense weather conditions (compared to 34% in the Rocky Mountains and 16% in the Coast Mountains). Almost three quarters of the fatal incidents, between 1984 and 2003, occurred in the triangle between Vancouver Island, Pincher Creek and Hinton, Alberta, an area with a high level of recreational activity.

Factors Common to Recreational Incidents
While avalanches can happen at any time under various conditions, listed below are the factors that are most common to avalanches involving recreational avalanche incidents:

  • Generally clear skies, little or no snowfall and light or calm winds
  • Dry slab type avalanches, with an average thickness of less than 100 cm
  • Triggered by victims or members of the victim's party
  • The weak layer often consists of surface hoar, facets or depth hoar
  • Starting above or near the tree-line on lee or cross-loaded slopes with rocky ground cover
  • On 30-40° slopes, often at a convex part of the slope

Awareness of these factors and others may help recreationists select terrain appropriate to the snowpack and weather conditions. Since the interaction between snowpack and terrain can be subtle, route selection and stability assessment remain crafts learned over many years.

Residential, Industrial and Transportation Incidents
The number of residential, industrial and transportation incidents due to avalanches has steadily declined over the last century. While the few fatalities that occur are of main concern, a notable aspect of these types of incidents is the financial losses averaging $350,000 per year. Typically, costs reported incurred are due to repairing and replacement of damaged property, but do not include road closures and lost revenue.

Survival Factors and Search and Rescue
While there is always the risk of being caught and buried in an avalanche when traveling in avalanche country, the chances of surviving an avalanche are about 86%. This number depends on several factors, including an ability to remain near the surface, the terrain, the size of the avalanche, time until rescue, and luck.
Asphyxiation is the leading cause of avalanche deaths, and as such a buried victim is unlikely to survive if the others in the group have to seek the assistance of a rescue agency. That is why training in the use and detection of avalanche transceivers, and most importantly, wearing them in the backcountry, provides the most effective method of locating a buried victim.

From Avalanche Accidents in Canada Volume 4: 1984 - 1996. Supplemented October 2007 with data from the Canadian Avalanche Association.

Factors Contributing To Recreational Avalanche Incidents
There are a number of common mistakes that many backcountry recreationists make that put them at increased risk of being involved in an avalanche accident. These include:

  • Poor trip preparation
  • Lack of knowledge of recognizing avalanche terrain
  • Inability to assess snow stability
  • Unskilled backcountry search and rescue techniques

The basics of these skills, however, can be learned through avalanche awareness courses or by traveling with experienced people, and then refined over successive winters.

Other sources of information available to backcountry travelers can be found from many sources including the Internet, guidebooks, maps, information centers, and people who have been in the area.

Increasing Chances of Survival Through Risk Avoidance
Avoiding putting yourself at risk plays a large part in eliminating as many factors as possible that contribute to avalanche incidents. To this end, understanding the causes of being caught in an avalanche and anticipating them before and during the trip need to be considered. Steps that can be taken to do this include:

  • Designating a leader to help ensure effective decision-making
  • Putting people at front of pack who are skilled at assessing snow stability or selecting routes
  • Ensuring that “back in the pack” people don’t simply follow the track, but pay attention to the terrain or snowpack
  • Don’t fall into the “blue-sky” attitude that draws recreationists to upper slopes where unstable snow can remain days or weeks after a storm
  • Don’t focus on being goal oriented even after learning of unfavorable conditions such as rain, heavy snowfall, drifting snow, 0° C temperatures and poor visibility
  • Knowing when you are tired so that fatigue doesn’t cloud judgment and narrow the margin of safety
  • Recognizing that a sense of “it won’t happen to me” invincibility can be fatal

It is important that experienced members of a group assume the lead in determining where, when and if to proceed on a backcountry trip. Taking the opportunity to get together during the trip for important decisions on assessing snow stability, the route, and possibly changing weather conditions is always advisable. Sometimes a quiet voice asking, “But why do we think that slope is stable?” can prompt a careful re-assessment of the situation and lead to a sound decision. Also, involving less experienced people in route selection and stability assessment contributes to the experience of every person in the group that will pay off on subsequent trips.

From Avalanche Accidents in Canada Volume 4: 1984 – 1996.

 

 

 

related attachments

  • Avalanche Accidents in Canada Volume 4

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  • Avalanche Accidents in Canada Volume 3

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  • Avalanche Accidents in Canada Volume 2

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  • Avalanche Accidents in Canada Volume 1

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