Risk analyses for dry snow slab avalanches released by skier triggering

Since human triggering is responsible for about 90 % of deaths from slab avalanches in Europe and North America, risk analysis is very important for skier triggering of avalanches. The depth to the weak layer and the slope angle are two key measureable quantities prior to dry slab avalanche release. Both are important in risk analysis. The probability of avalanche release dramatically increases as the slope angle increases above 25°. As the slab depth increases, the consequences increase rapidly if an avalanche releases. Simple risk analyses for skier triggering were done for both slope angle and slab depth. The slab depth analysis showed there is a range of about 0.6–1.0 m for which the risk of death is highest. For slope angles, the range with highest risk was shown to be 33°–45° within the known range (25°–55°) for skier-triggered avalanches. Copyright Springer Science+Business Media Dordrecht 2014