Author(s): Daniel Caviedes-Voullieme; Mario Morales-Hernandez; Ibai Lopez-Marijuan; Asier Lacasta; Pilar Garcia-Navarro
Linked Author(s): Pilar García-Navarro
Keywords: River bed bathimetry; Digital Terrain Model; Shallow Water equations
Abstract: The accurate numerical simulation of river flow by means of 2D shallow-water model requires a large amount of topographic data to build a sufficiently accurate Digital Terrain Model (DTM). The DTM must fully cover the possible flooded area as well as the main channel (or channels) of the river. It is common to find DTM's for large floodplains generated by LIDAR flights. However, for rivers with base flow discharge, it is impossible to obtain LIDAR data of the river bed, since it is permanently flooded. These areas are sometimes surveyed using SONAR technology, thus obtaining very detailed bathymetry, but more often, they are surveyed only by obtaining discrete cross-sections of the river channel. These cross-sections do not provide 2D information to cover the entire flooded area of the river channel, thus, it is necessary to generate the missing information. In this work an algorithm to generate the missing information for the areas in between cross-sections is proposed. Using the 3D coordinates of the cross-sectional points. first, the trajectory of the channel is interpolated in the horizontal plane and then the river bed elevations are interpolated following the trajectory of the channel to produce a 3D surface of the river channel. The information is then joined with the LIDAR data to produce a complete DTM. The algorithm allows to generate a river bed which preserves important morphological features such as meanders, thalweg trajectory following the concave banks of meanders and gravel beaches in convex banks. The proposed algorithm is tested using a synthetic river floodplain as well as real floodplains in the Ebro river in northeast Spain. The resulting geometries are analyzed and sensitivity to input data is studied. 2D shallow-water simulations are performed and the effects of the interpolation on the river hydrodynamics are assessed.
Year: 2013