Climate changes and debris flows in periglacial areas in the Italian Alps

Debris flows pose major hazards in many mountainous regions. The most apparent influence of climate changes on debris flows is related to variations in the precipitation regime. In glacial and periglacial areas, also glacier retreat and permafrost degradation have a major role in debris flow occurrence, as they can substantially increase the availability of erodible debris and provide the conditions for sudden water release. The paper analyses some recent debris flows in periglacial environments in the Italian Alps. The study is based on field observations and on the comparison of present geomorphic conditions with those that existed before the glacial retreat of the last decades. The results of researches on climate changes in Italy indicate that the studied debris flows occurred in the frame of a general trend of increasing temperature. In this context, debris flows in periglacial areas should be viewed as a particular aspect of geomorphological and hydrological changes driven by climate changes in alpine headwaters. Most of studied debris flows have been caused by rainfall. In these cases, the influence of cryosphere degradation essentially consists in an increased availability of mobilisable material. Other processes, which trigger debris flows in areas affected by glacial shrinkage, are glacial lake outbursts and the melting of ground-buried ice.