Assessing short term erosion-deposition processes of the Brenta river using LiDAR surveys

The extent and amount of erosion and deposition processes experienced by the Brenta river after the flood events of November and December 2010, have been assessed on the basis of DTMs derived from LiDAR surveys made before (2010) and after (2011) these floods. The study, carried out on three sub-reaches of this regulated gravel-bed river took advantage, beside LiDAR elevation data, two relatively novel approaches for channel bathymetry and uncertainty calculation. The first one allowed us to obtain the elevations within the wetted channels while the second method allowed the quantification of uncertainty related to the various phases of the topographic representation process. The erosion-deposition volumetric results derived from the two years DoD differencing models highlighted the impact of the two floods. In all the sub-reaches, erosion processes have dominate and featured a decreasing downstream trend, being the lower reach in a nearly equilibrium condition. The quantitative results of morphological changes have emphasized the evidence that relevant flood events (RI > 10 years) in high regulated gravel bed-rivers, encourage erosion rather than deposition patterns.