Investigation and numerical simulation of debris flow events in Rochefort basin (Aosta Valley—NW Italian Alps) combining detailed geomorphological analyses and modern technologies

This paper presents a multidisciplinary approach using modern technologies for the analysis and modelling of the debris flow that occurred at Torrent Rochefort (Aosta Valley—Italy) September 2015. A detailed on-site geological and geomorphological study was performed to highlight the main characteristics of the basin, useful for validating and calibrating dynamic simulations. The total mobilized volume was estimated by comparing a pre-event DTM and a post-event DTM generated from an unmanned aerial vehicle. A digital terrain model comparative analysis provided a quantitative estimation of erodible depths in different sectors of the Rochefort basin. Numerical modelling of the event was performed using the continuum mechanics-based code RASH3D that enabled a simulation of the dynamic debris motion on complex topography. The results demonstrate the importance of a detailed geomorphological study for the validation and calibration of numerical results. Finally, some considerations were inferred about the magnitude of unstable debris and the possible consequences on local infrastructures.