DEM resolution and stream delineation threshold effects on the results of geomorphologic-based rainfall runoff models

Abstract

Digital elevation model (DEM) resolution and the assigned threshold for river network delineation aect the results of rainfall-runo models. In this study, the eects of these 2 issues on the extracted geomorphologic parameters of watersheds and the performance of a kinematic wave based model, called KW-GIUH, are investigated. The results show that by decreasing the DEM resolution at xed thresholds, parameters such as subbasin mean slope and the number of streams decrease and the area of the ith order subbasins and the mean length of the overland ow increase. Moreover, the results indicate that the reduction of the DEM resolution at a xed threshold causes the peak ow and hydrograph time base to decrease up to the cell size of 100 m and then, after experiencing a jump, again decrease with the increase of the cell size. According to the achieved results, above the threshold of 2%, the dierence between the peak ows of dierent hydrographs at dierent resolutions is meaningful. The KW-GIUH sensitivity to DEM resolutions and thresholds is sharper in peak ow and then in hydrograph time base and time to peak. At a xed threshold, the value of time to peak