A simple method for the enhancement of river bathymetry in LiDAR DEM

The preparation of an accurate bathymetry is crucial for flood modeling and is usually done using a LiDARderived Digital Elevation Model (DEM). However, a recurrent flaw of LiDAR DEM is the presence of water along rivers, that prevents a careful reproduction of the river bed and channel conveyance. This paper provides a simple and effective algorithm to tackle this problem when ground surveyed cross sections are available to complement DEM data. In contrast to most interpolation approaches, the algorithm is physically-based, using a 2D Shallow Water Equations solver in the identification of the wetted river bed perimeter. The method was applied to a 37 km long stretch of the Mella River (Northern Italy) providing satisfactory results. Further examples show the potential of the method in cases of increasing complexity of riverbed bathymetry. The procedure is explained step by step in the supplementary material, using two widely used freeware software.