Application of a new method to improve river cross sections derived from satellite images

Abstract: In hydrological and hydraulic modelling, river geometry is a crucial input data. Recent investigations have been looking at methods to improve the description of cross sections extracted by DEM derived by satellite images. SRTM derived DEM are often lacking precise information as the sensors cannot detect the submerged river parts, but, on the other hand, it is available on a global scale which makes it very attractive and useful, especially in data scarce regions. This study aims at applying the so called “slope break” method to improve river cross section geometry extracted from SRTM DEM. The report is divided into three parts: a) The making of a Matlab-code to improve cross sections geometry extracted by satellite derived DEM; b) an application of the code to real cross-sections from the river Po in Italy and c) hydraulic simulations with and without SRTM modified cross sections to test the performance of the method, in collaboration with senior colleagues. The Matlab successfully performs the slope break point and finds, when appropriate, the approximated lowest point zmin of the cross section below the water surface. The comparison of the river geometry of the modified SRTM cross sections versus LiDAR available cross sections show the good performance of the method in improving the river geometry description. This code can simplify the work and improve many SRTM river cross sections in an effective way. The hydraulic simulations performed with and without the modified cross sections show how the modified SRTM model improves when compared to LiDAR results