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 affect the results of rainfall-runoff models. In this study, the effects 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 fixed 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 flow increase. Moreover, the results indicate that the reduction of the DEM resolution at a fixed threshold causes the peak flow 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 difference between the peak flows of different hydrographs at different resolutions is meaningful. The KW-GIUH sensitivity to DEM resolutions and thresholds is sharper in peak flow and then in hydrograph time base and time to peak. At a fixed threshold, the value of time to peak is independent of DEM resolution.

Keywords: DEM resolution, KW-GIUH, thresholds, peak flow, hydrograph base time, time to peak

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