Slope instability and flood events in the Sangone valley, northwest italian Alps

Slope instability and streamflow processes in the mountainous part of the Sangone river basin have been investigated in conjunction with their influence on relief remodelling. Through historical records, the most critical sites during extreme rainfalls have been evidenced, concerned natural parameters and their effects (impact on man-made structures) reiterated over space and time. The key issue of the work is the simulation of a volume of detrital materials, which might be set in motion by a debris flow. Two modelling approaches have been tested and obtained results have been evaluated using Debris© (GEOSOFT s.a.s.) software. Simulation of debris flow in a small sub-catchment (Tauneri stream) was carried out and the thickness of sediment "package" that could be removed was calculated in order to assess the debris flow hazard. The Turconi & Tropeano formula (2000) was applied to all the partitions of the Sangone basin in order to predict the whole sediment volume which might be delivered to the main stream during an extreme event and the result being 117 m3/hectare.