Mountain permafrost and recent Alpine rockfall events : a GIS-based approach to determine critical factors

Glacier retreat and permafrost changes, as related to climate change, are supposed to affect stability conditions of steep rock walls in cold mountain ranges. Several rock-fall events, which have occurred in the European Alps during the 20 th century, are possibly related to warm permafrost. This study undertakes a systematic parameterization of rock-fall events in order to increase information about thermal and topographic conditions under which rock instabilities develop in areas of mountain permafrost. Thermal conditions of historically documented starting zones are parameterized by applying either empirical rules or GIS-based spatial models; slope is derived from DTMs. Despite the relatively small number of events documented so far (around 20), the first results presented clearly indicate that the factor ‘permafrost’ must be considered in connection with rock-falls from high mountain slopes. Table 1. Geomorphometric parameters of the rock-fall events considered. The altitude relates to the uppermost point of the starting zone. H is the fall from the top of the scarp to the bottom of the accumulation, L the corresponding horizontal travel distance. The star in column Gl. indicates events that are situated in a glacial environment. n. Name Date Altitude Aspect Volume H L H/L Gl. Reference ______ ______ __ __ m a.s.l. 10 6 . m 3 m m 1 Triolet (I) 1717 3600 E 16-2