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Avalanche risk management in backcountry skiing operations Grímsdóttir, Harpa

Abstract

Over the last 34 years Canada has had an average of 11 avalanche fatalities per year and during the past five years this average has increased to 16 fatalities per year. Today, avalanche accidents happen primarily to people during recreational pursuits, and about half of the victims over the last 20 years were backcountry skiers. Backcountry skiing operations in Canada are making a constant effort to improve their avalanche safety. This study is based on data from a large heli-skiing operator in Canada; Canadian Mountain Holidays (CMH). The first objective of this study was risk analysis based on data from CMH's database, Snowbase. Skier triggered avalanches were analysed in term of factors such as elevation level, aspect, stability rating and the time of the year. When looking at human triggered avalanches, it is not possible to analyse the risk associated with these factors based on avalanche data alone; it is essential to have an idea about where and when people are skiing. Fortunately, Snowbase also contains information about the usage of defined ski runs within the operation areas, and therefore it is possible, perhaps for the first time, to extract some ideas about the relative risk associated with the different factors. The study shows that the historical risk of accidentally triggering an avalanche greater than size 1 depends highly on the stability rating, with the highest risk under "poor" stability. The risk is greater in higher elevation levels than lower down, and it is lower during late season than earlier on. The risk does not depend as much on aspect as may be indicated from avalanche data alone. However, it is relatively high in the N-NE-E sector. These factors are not independent of each other so analyses of combined factors were also performed. The second objective was to extract knowledge on avalanche risk management from professional mountain guides. Questionnaire and interviews with professional mountain guides were used as the tools for that, as well as observation of guiding in action and analysis of remarks in avalanche reports. The focus was on terrain selection and group management in terms of avalanche risk. My study indicates that when selecting terrain, guides first look at the overall shape and size of the terrain, but avalanche history of terrain and inclination are also important factors. Group management is an important part of avalanche risk management and the most important tools used by the guides are instructions to guests and the selection of regrouping spots. Experience is a significant factor in both terrain selection and group management. The third objective was to look at the possibility of using rule based decision methods for professional mountain guides in Canada. The result was that strictly rule based methods are not appropriate, because the guides are most likely able to make better decisions, and take more factors into account, based on their experience. However, some structure is desirable for the decision making process, in order to minimize the risk of human error, and among guides, some structure already exists. Based on the results from the first two objectives of the study, reccommendations are given in the form of suggestions rather than rules.

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