EFFECTS OF MESH AND SURVEY RESOLUTION ON 2D NUMERIC HYDRODYNAMIC MODELLING IN A MOUNTAIN RIVER

摘要

For 2D hydrodynamic modelling the representation of river bathymetry has an influence on predicted hydraulic conditions. Modelling results depend on the accuracy and resolution of bathymetric survey data of the stream channel and surrounding floodplains. In this study the effects of the topographic representation by mesh resolution and survey resolution of the bathymetry a mountain river in Italy were investigated. High resolution bathymetric data acquired by Airborne Laser Scanning with a water penetrating Laser system were available for the investigated river reach. On the basis of the high density data, different cross-section based data sets were created from high to low detail of riverbed representation. These data sets were interpolated on 2D numerical calculation meshes with different mesh resolutions to test the effects of mesh and survey resolution and their interactions on modelling results. The ability to predict water levels, water depth and flow velocities as well as inundated extents and the ability to capture hydraulic features like horizontal recirculation zones were compared. Also the effects on calibration results are discussed and calculation time was examined within this work. Survey data of the water level covering the study reach were available for three different discharge conditions to calibrate the models. Calibration was realized using measured water levels for adjusting roughness parameters to meet the target values.