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 LiDAR-derived 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. • Water hinders a careful reproduction of the actual river bathymetry by LiDAR •A simple physically-based algorithm is proposed to tackle this problem in DEM •The method requires a set of surveyed cross sections, a GIS, and a 2D SWE solver •The method is also effective for complex layouts such as braided rivers •An example guides the reader step by step, using two widely used freeware software