Effects of spatial grid resolution oil river flow and surface inundation simulation by physically based distributed modelling approach

Grid-based distributed hydrological models are considered to be a very effective flood modelling tool for basin-wide flood risk analysis because of their capabilities of simulating river and surface inundations at high spatio-temporal resolutions by taking advantages of grid-based data from meteorological models, radar and satellite remote sensing. Selecting an appropriate and size is critically important for any application of a grid-based model, which requires proper understanding of effects of grid sizes on simulated outcomes. The paper presents the Outcomes of a study conducted to analyse the effects of grid resolution on simulated river peak flows and surface inundation in two selected river basins using a process-based distributed hydrological model. The outcomes show that grid resolution significantly affects the simulated river peak flows and surface inundation characteristics. In both cases, it has been found that the effects are mainly caused by changes of the topographic parameters as a result of changes of grid sizes. The reduction of average Surface slope with the increase of grid size affects the simulated surface inundation extents and heights. There is a threshold resolution of digital elevation model (DEM) in the simulated flood inundation and beyond that the model Outcomes become arbitrary. Averaged topographic values at coarse resolution beyond this threshold level do not represent any characteristics of locally elevated topographic features such as dykes, highways, etc. and their influence on flood inundation characteristics can be no more captured by the model. Copyright (C) 2008 John Wiley & Sons, Ltd.