Geomorphic change detection in Gadria-Strimm and Moscardo catchments, Italy

Methods devoted to the assessment of geomorphic changes can be used to identify geomorphologically unstable areas, to quantify processes intensity, and to compute sediment budgets. Digital elevation models (DEMs) built from repeated topographic surveys can be used to produce DEM of Difference (DoD) maps whose analysis allows to study morphological changes in slopes and channels from the quantitative (scour and fill changes in volume) and the qualitative (spatial patterns of erosion and deposition) perspectives (Scheidl et al., 2008; Theule et al., 2012; Picco et al., 2013). The activity carried out by CNR IRPI (PP4) in the frame of the SedAlp project focused on the analysis of multi temporal high-resolution Digital Terrain Models (DTMs) derived by Airborne and Terrestrial LiDAR. The aim is to analyse surface changes due to erosion and deposition in a bedload and two debris-flow prone basins in the Eastern Italian Alps (Strimm, Gadria and Moscardo pilot areas). The analysis was carried out at different temporal and spatial scales basically related to the typology of the adopted surveying method. In Gadria and Strimm catchments, where two airborne LiDAR (2005 and 2011) are available, geomorphic changes induced by debris flows and landslides were investigated at catchment scale. DoD results have been then compared with field estimations stored in a historical database. In the Moscardo catchment, Terrestrial Laser Scanner (TLS) has been used to survey three representative areas of the catchment in a small time window (August 2011-October 2012). Results of volumetric budgets of the surveyed sediment source areas derived from DoD analysis have been compared with debris-flow volumes estimated from flow stage measurements at the instrumented channel reach.