STANDARD METHODOLOGY TO STUDY DEBRIS FLOW HAZARD AND RISK MITIGATION IN ALPINE BASINS

In 2005, the public administration of “Regione Autonoma Valle d'Aosta” (Italy), according to a specific program of hydraulic and geological risk prevention and prediction, developed a strategy to evaluate the debris flow hazard mapping in 155 cone areas, in order to define new measures, in addiction to the existing ones, to reduce the potential risk of debris flow. The starting point of the evaluation process was focused on the flood and landslide hazard maps already available before 2005, concerning the different municipalities of the entire Region and designed according to the regional urban planning law. The analysis of these maps, and in particular the urban areas exposed to high or medium levels of flood and landslide hazard, defined the list of the most dangerous fans to investigate. The list of fans to be studied includes those in which were recorded historical events of debris flow. The 155 fans, classified by their high-medium level of hazard, have been studied from 2005 to 2010 by 34 different groups of professionals consisting of an engineer, an agronomist and a geologist. A technical scientific supervisor group coordinated the study activities, according to a specific methodology in order to get a homogeneous level of analysis in the 34 different group.