Characterization and Modeling of a Debris Flow in a Dolomitic Basin: Results and Issues

Debris flows are rapid gravity-induced flows of high-concentration granular-liquid mixtures, consisting of clay, silt, sand and boulders with a variable quantity of water. Due their high speed and energy, they represent a severe hazard in mountain regions. In this study, we investigate the properties and the dynamic of a debris flow occurred on 29th August 2003 in Valcanale valley (Friuli Venezia Giulia, Italy). Among the many watersheds affected by debris flow during the catastrophic alluvial event, we have chosen a dolomitic one, called “Solari” stream. Grain size, mineralogy and rheological behavior were characterized through laboratory analysis; later two-dimensional simulations, using the Flo-2D software, were performed on a 5 × 5 m grid obtained by the extrapolation of elevation values of the Regional Technical Map (CTRN), surveyed in 2003, in order to replicate the event, and on a 5 × 5 m grid obtained by the resampling of a LiDAR DTM, surveyed in 2008, to test the efficiency of the mitigation works. This work points out the safety of the infrastructures downstream, protected by an adequate deposition basin. At the same time, it underlines some issues during the rheological analysis and the overestimation of the depositional extent of the debris flow, when the laboratory data were used to run the simulations.