FUNZIONE DEL BOSCO NELLA FASE DI ARRESTO DEI DEBRIS FLOW

Debris flows, a flowing mixture of sediments, water, air and other materials, are one of the most destructive events in mountain areas: damaged buildings, interrupted infrastructures, fatalities are only some examples of their effects . In Northern Italy, for example, 36% of fatality events in the field of hydro-geo-morphological hazards is represented by debris flows. Alluvial fans, which have been just built by debris flow events occurred in the past, in fact, are areas where human activities (homes, factories, etc.) have always been developed. People living in mountain areas, in this way, must adopt expensive and impacting technical devices to prevent or to mitigate this phenomena. When the magnitude of debris flow is quite small, the protective capability of forests can be used to mitigate their destructive power. Due to the cost and to the environmental impact associated to the technical works, public administration in some areas of the Alps developed knowledge and guidelines to manage forests in a protection perspective. Few studies concerning the quantification of the protection effect, however, have been carried out especially for debris flow phenomena. In the present work small scale tests have been carried out in order to quantify the wood’s effect in the process of debris flows deposition. Results, in particular, show that trees can significantly influence deposit’s run out and area (two of the main debris flow’s deposition parameters), if their density is appropriate with respect to debris flow characteristics. Such evidence should represent the starting point for future researches which aspire to develop guidelines for protection forest’s maintenance in mountain areas.