Rischi connessi con la dinamica glaciale nelle Alpi italiane

Glacial hazards in the Italian Alps

Abstract

Glaciers are dynamically very active physiographic units, in which instability phenomena may take place. They are to be feared owing to the rapidity of their development, sometimes without any easily identified forerunning phase. The consequent danger hazard is to a great extent underestimated, especially during the present phase of generally retreating o stationary glacier snouts. However, recent events (ice fall of the Upper Coolidge Glacier on Monviso, outburst from emptying of englacial water pocket of the Rochefort Glacier, and sudden discharge of the proglacial Locce lake) should draw our attention to these phenomena. Although less common than others of the alpine environment, such as landslides, avalanches, debris flows, they show a local high concentration in very small geographic areas. In this paper the most significant historical events (about 90) concerning the Italian Alps, are reviewed. On the basis of the case typology thus obtained, the following phenomenon classes have been distinguished: 1) ice fall from snout of glaciers; 2) supraglacial debris fall/slide outside the lateral moraine; 3) landslide involving ice; 4) rapid advance of snout of glacier; 5) emptying of internal water-pocket; 6) emptying of proglacial lake; 7) emptying of ice-dammed lake. For each class a list of the cases taken into consideration is given, listing, when possible, some basic morphometric parameters (involved volume, run distance, and overcome level difference), data concerning the cinematic features (development times) and geomorphologic effects and damages produced. Furthermore, a short description of a phenomenon case for each typology, generally the nearest to us in time, is given, for which it has been possible to perform a deeper field investigation, referring to the literature for some cases. Finally, the relationship between different typologies and the hazard levels are analyzed.