Simulation of the debris flow occurred the 15 August 2010 on Rio Val Molinara Creek (northeast Italian Alps)

Abstract

On the early morning of 15 August 2010, a runoff-generated debris flow routed along the Rio Val Molinara Creek and inundated the village of Baselga di Piné (Autonomous Province of Trento, northeast Italy) with about 50000 m3 of debris. Post-event field surveys allowed both the identification of the initiation area, and the estimate of the average erosion-deposition depths on different zones of the affected area. On one hand, the map of erosion-deposition depths along the Rio Val Molinara Creek was obtained by subtracting the corresponding pre- and post-event DEMs elevation values, interpolated by using the LiDAR data of two aerial surveys carried out in 2007 and 2011, respectively. On the other hand, the map of debris deposits on the inhabited fan was obtained by integrating the direct post-event field estimates and photo interpretation. In the research, the studied debris-flow event was simulated from the triggering to the inundation through a models cascade, which relies on the sequential application of rainfall- runoff, triggering, and routing models. After that, the routing model results were compared with the observed erosion-deposition pattern in order to assess the reliability of the proposed approach. In detail, the runoff was simulated in the initiation area and then used for building the solid-liquid hydrograph. After that, the solid-liquid hydrograph was routed downstream by means of a bi- phase GIS-based cell model, previously parametrized by using approximately the same values employed for the back-analysis of two debris-flow events occurred in the Dolomites (northeast Italian Alps). The comparison between the observed and simulated erosion-deposition depths and volumes is quasi-satisfactory. This is an important research outcome since the reliability of both debris-flow hazard assessments and risk analyses based on routing models relies on the trustworthiness of model simulations. In addition, due to the scarcity of pre- and post-event topographic surveys, the map of erosion-deposition depths might become a precious data source for testing the predictive capability of debris-flow routing models proposed in the literature by other authors.