Bossi G., Cavalli M., Quan Luna B., Frigerio S., Mantovani M., Marcato G., Schenato L., Pasuto A, 2013, Multi temporal LiDAR-DTMs as a tool for modeling a complex landslide_ a case study in the Small Dolomites (Rotolon catchment – Italy), 8th International conference (AIG) on Geomorphology., pp. 682, Parigi (Francia), 27-31 Agosto 2013,
URL: http://www.cnr.it/prodotto/i/264448

The geomorphological change detection through the comparison of repeated topographic surveys is a recent approach that greatly benefits from the latest developments in topographical data acquisition techniques. Among them, airborne LiDAR makes the monitoring of geomorphological changes a more reliable and accurate approach for natural hazard and risk management. In this study, the analysis of multi temporal LiDAR-DTMs acquired just before and after a complex landslide event (4th November 2010) in the Rotolon catchment (Small Dolomites, Italy), was used to set up the initial condition for the application of a dynamic model. The 2010 event detached a mass of 320.000 m3 from the south slope of Mt. Rotolon partially evolving in a debris flow that stretched for 4.5 km threatening some villages. Pre- and post-event DTMs derived from LiDAR with 2 m resolution were available. The comparison between the DTMs was carried out considering the error propagation. The resulting differential DTM was analyzed in order to identify erosion and depositional areas related to the event and to quantify them in terms of volume. The knowledge of the dynamics of the phenomenon allowed to back-analyze the event with a dynamic numerical 3D model. DAN3D code was selected because it allows to modify the rheology and the parameters of the moving mass during the run-out. This behaviour was observed along the path of the debris-flow where the mobilized mass encountered rheological modifications due to the hydric contribution of tributary streams and the entrainment of eroded material. Considering these aspects a sound simulation of the 2010 event was computed. Nowadays some portions of Mt. Rotolon flank are still moving and showing precursor signs of detachment. The same soil parameters used in the back-analysis model were used to simulate the run-out for three possible landslides flows allowing to generate reliable risk scenarios that could be used for creating civil defense emergency plans.

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