Item: Avalanche incidents in switzerland in relation to the predicted danger degree
Title: Avalanche incidents in switzerland in relation to the predicted danger degree
Proceedings: 2002 International Snow Science Workshop, Penticton, British Columbia
Authors: Stephan Harvey, Swiss Federal Institute for Snow and Avalanche Research (SLF), Davos
Abstract: All known avalanche incidents from 1987/88 to 1998/99 (12 years) have been analyzed with respect to the scale of avalanche danger of the Swiss avalanche bulletin (European danger scale 1-5). The database contains information of 1800 avalanches causing damage to people and property. 45 % of fatal avalanche accidents occurred at danger degree "considerable" (level 3), 30 % happened at "moderate" (level 2). The mean size of the spontaneous avalanches causing an incident increases with the danger degree. For degree "low", "moderate" and "considerable" the fracture depth is 50 to 60 cm, for "high" and ''very high" the depth is 150 cm. On the other side for human -triggered avalanche accidents, the avalanche size and fracture depth does not depend on the danger degree level. The inclination of the starting zone of these avalanches is 39° for all danger levels except level "low", where it is 41 0. At danger level "considerable" 24 % of all human triggered avalanches occur under 35° inclination, at "moderate" there are 18 %. Human-triggered avalanche accidents are more or less the same size and occur in similar terrain independent of the avalanche danger degree. Most avalanche accidents on ski tours and most accidents with experienced people occur at level 2 ("moderate "). The largest number of avalanche accidents in out-of-bound terrain (off piste) happens at level 3 ("considerable"). The ratio between the number of injured or killed people to the number of days at which a given danger degree occurred can be used as a risk index". It turns out to increase exponentially with the danger degree.
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Keywords: avalanche accident, avalanche incident, avalanche accident statistics, avalanche forecast, avalanche bulletin, avalanche danger degree
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