Avalanche accidents in back country terrain of the Swiss alps: new investigations of a 30 year database

Abstract

More than 1000 avalanche incidents involving skiers, snowboarders and mountaineers in the back country terrain of the Swiss Alps have been filed in an electronic database. New results concerning accidents on ski-tours and out of bound-skiing (off-piste) can be presented.<br />\n95 % off all avalanche accidents were human triggered. In 60 % of the cases the first person in the slope triggered the avalanche. In 30 % of the accidents ski tracks from the same day of the avalanche were present in the slope, in 10 % older ski tracks were found in the slope. Although the same amount of accidents on ski-tours occurred on descent as on ascent, 50 % more people got caught while ascending. The typical victim is male, between 17 and 30 years old. Fatal avalanches are larger than those where nobody got killed. Analysis of complete burials shows that people are more affected on multiple burials than expected.<br />\nOn 24 days in the last 30 years 4 or more avalanche accidents happened on a single day. Many accident-days occurred after new snow, strong winds with weak snow pack layers. In 20 % of the days there was neither a significant amount of new snow, nor strong winds, but an increase of temperature. On these days the mean predicted avalanche danger was the lowest.