DESTRUCTIVE SNOW AVALANCHES AND CLIMATE-CHANGE IN THE SWISS ALPS

Snow avalanches are an important natural hazard in alpine areas. Espec ially settlements and traffic routes are threatened. A better understa nding of the relations between avalanche occurrence and climate is nec essary to deduce possible effects of climate changes on the avalanche hazard. This study investigates the relations of climatic conditions o n avalanche release from 1947-1993 and extreme snowfall events from 18 96-1993. The statistical evaluation of the meteorological data shows a long-term trend in temperature, but not in snow depth and extreme sno wfall events. From the meteorological long-term time series at Davos ( eastern Switzerland) we tried to model the corresponding avalanche act ivity from 1896-1946. The modelling of the avalanche activity was not successful because the extremely sparse distribution of extreme events prevented the establishment of a reliable statistical model. Looking at potential avalanche situations in terms of extreme weather situatio ns it can be assumed that the climatic causes for severe avalanche per iods have remained stable during the past 100 years and show no sign o f change in the near future. However, the construction of defence stru ctures in avalanche starting zones, improved zoning of hazardous areas and artificial avalanche release have reduced the probability of cata strophic events.