Effects of data resolution and stream delineation threshold area on the results of a kinematic wave based GIUH model
This research addresses the effect of using digital elevation models (DEMs) derived from different sources on the results of a kinematic wave based GIUH model. DEMs from different sources exhibit data-resolution effects on the important derived geomorphological properties of watersheds used in rainfall–runoff modelling. Using DEMs derived from topography maps (TOPO DEM) and the SRTM DEM, it was illustrated that different threshold areas for stream network extraction affect GIUH model performance. The results show that the SRTM DEM gives higher values for sub-basin and channel slope as well as number of streams, than the TOPO DEM, while mean length of overland and channel flow is greater for the latter source. The results also indicate that peak flow and slope of the hydrograph rising limb obtained from the SRTM DEM at different threshold areas (ranging from 0.25% to 3%) are greater than that for the TOPO DEM. Investigating the effects of stream network delineation threshold area on the simulated peak flow shows that the maximum and minimum differences (12% and 1%) occur at the threshold areas of 0.5% and 1%, respectively, while for threshold areas higher than 2% the difference in peak flow of the two sources is limited to 10%. Based on the results of this research, it is deduced that the effects of data resolution and stream network delineation threshold areas on the geomorphological parameter values and the performance of GIUH-based models are significant and should be considered when using SRTM DEMs in ungauged watersheds.
Keywords: SRTM DEM, topographic maps, rainfall–runoff Modelling, KW-GIUH, threshold area