On Probabilities of Avalanches Triggered by Alpine Skiers. An Empirically Driven Decision Strategy for Backcountry Skiers Based on These Probabilities
Christian Pfeifer
Institute of Statistics, University of Innsbruck, Innsbruck, Tyrol, Austria

Most fatal avalanche accidents in the Alps are caused by skiers and snowboarders. It has been one aim from the beginning to give guidelines for backcountry skiers in order to avoid avalanche accidents. About 10 years ago, the mountain guide Werner Munter developed a strategy for backcountry skiers whether to go or not to go on a skiing tour. However, this decision strategy has a lack of empirical evidence because he does not take into account incidents without avalanche accidents. This presentation proposes an empirically driven decision strategy for backcountry skiers based on probabilities of a logistic regression model. We used the explaining variables danger level, incline of the slope and aspect of the slope, which turned out to be the most important one. Additional information on frequencies of skiers on slopes under specific conditions is included in the model. Accident data and avalanche forecasts in Tyrol reported by the Tyrolean avalanche information service within three seasons (1999-2002, 497 days of observations) are used for model building.

The probabilities of the model provide quantities, which can be seen as remaining or residual risks (see Munter). Our proposal shows more or less strong correlation with Munter's method. However, the aspect of the slope seems to have not that effect that is widely believed.

Keywords: Avalanche risk management; Human triggered avalanches; Decision strategy; Logistic regression model

Biography: Studies in mathematics Ph.D.: 1992

Habilitation (venia legendi) Statistics: 2010