Effetti degli eventi alluvionali nell’ambiente glaciale: la sovraincisione della morena del Ghiacciaio del Mulinet (Bacino della Stura di Valgrande, Alpi Graie)

Failures induced by heavy rainfall in proglacial environment: the downcutting of neoglacial moraine of Mulinet Glacier (Upper Valle di Lanzo, Western Alps)

Abstract

Recently areas close to the snout of several Italian glaciers have been the starting zones for debris flows triggered both by heavy rainfall associated with melting of ice and snow to unusually high elevation in glacierized basins and by sudden emptying of englacial or proglacial lakes. The well-known mobility of debris flows has been emphasised by the high potential on energy of the mountain slope and large amounts of readily available material and water. Even at great distance from the start zone, debris flow have reached inhabitated areas causing sometimes severe damage. For istance, in the north-western Alps, during a rainstorm in September 1993, a violent debris flow resulting from strong downcutting of a small stream on the face of the neoglacial moraine of Mulinet Glacier, travelled as far as 4.5 km and hit the village of Forno Alpi Graie. These high-energy geomorphic events are a potential glacier-related hazard that should not be underestimated, especially areas where alpine valleys are in developed for recreational use. Debris flow hazards related to glacial activity could become more important in the near future because of the increased availability of loose, erodible debris in areas recently exposed by glaciers, that are undergoing a phase of general retreat.