Integrating back analysis and forward modelling of a debris flow with GB-InSAR data to assess the risk in a mountainous valley floor

The 4th November 2010 debris flow event, detached from the Rotolon DSGSD detrital cover (Vicentine Pre-Alps, NE Italy) and channelized into the Rotolon creek riverbed, was modelled by means of DAN-3D numerical code. The debris flow travel distance was roughly 4 km, and many damages to hydraulic works and to four villages situated along the creek banks were reported. The back analysis of the 2010 runout showed that amongst all the available rheological kernels, the best one is the Voellmy-type. Varying the rheological reference parameters, in fact, the model could reproduce with high accuracy: i) debris flow impact area; ii) deposit thickness; iii) velocity; iv) final flow erosion volume. Based on the back analysis results, a forecasting analysis to assess the Rotolon valley exposure to possible future debris flow events was performed.