SENSITIVITY ANALYSIS OF THE 2D SOBEK HYDRODYNAMIC MODEL OF THE NIGER RIVER

Hydrodynamic models are used in flood modelling to estimate flood peaks, duration, flow time series and flooding extent. One of the most important components of a hydrodynamic model is the topography of the study area which is represented by the grid discretization. Sobek tool of Deltares was used to build the hydrodynamic model of the Niger Delta using SRTM DEM grids to replicate floods that had occurred in 1998, 2005, 2006 and 2007. The model was calibrated using frictional values for the channel and floodplain, and verified based on the 2007 Niger River flood map; and results showed flood location and partially the flood extent. With the availability of surveyed river bathymetry the topography was improved in discretization and the model was recalibrated. The model outputs (like flood peaks, flood extent and modelling time) based on different grid cell sizes show the model sensitivity to changes in the source of topography. A comparison of the two (old and new models) results is undertaken and a sensitivity analysis of the Sobek model to frictional and topographical change is presented. The model calibration conditions are also discussed.