Evaluating Hydrological Uncertainties Arising due to DEM Resolution: Study for the Himalayan River Basin Gandak

Abstract

Digital Elevation Model (DEM) is a most significant spatial input for the physical, hydrological models. Sometimes, the DEM resolution is needed to be changed to manage quick simulation in the large basins and to provide a pre-defined grid size required for a physical model. In such conditions, resampling of DEM data to specific grid size is shouted. In this study, the effect of DEM resolutions resampled with three methods (1) Nearest Neighborhood (2) Bilinear and (3) Cubic Convolution have been examined in the Gandak River Basin (GRB). The result for the GRB shows that stream flow is significantly affected by DEM resolution, where it overestimates the flow for coarser resolutions (DEM grid size >150m). T-test statistics demonstrates that the flow is significant at yearly time step for the coarser resolution (DEM grid size >500m) while it is insignificant at monthly time step.