The effectiveness of Clark's Instantaneous unit hydrograph model (IUH) on the spatial resolution of different digital elevation models

The current study evaluates the effectiveness of Clark's Instantaneous Unit Hydrograph (IUH) model from the accuracy of different Digital Elevation Models (DEMs) including TOPO, ALOS PALSAR, ASTER, SRTM and GTOPO in the Amameh watershed. For this purpose, at first, 34 rainfall-runoff events were selected. Also, the drainage network, the length and slope of the main river in each of the five DEMs were calculated using Arc GIS software. Then, the 30-minute isochrone map of the watershed was extracted using the spatial distribution of travel time method. Finally, the dimensions of Clark's IUH were estimated for each rainfall-runoff event and DEM. The results showed that with the decrease in the length of the main river following the decrease in DEM spatial resolution, the number of isochrone has been decreased, so that TOPO DEM has estimated the largest number of isochrone with the largest estimate of the length of the main river. The average percentage of the Relative Error (RE) of the runoff volume was estimated as 22.92, 26.68, 27.7, 32.15 and 35.66% respectively for the aforementioned DEMs. Regarding peak flow estimation, there is a significant difference between the average RE values in different DEMs. So that the lowest average value of the RE is related to TOPO DEM with a value of 31.7%. On the other hand, the Root Mean Square Error (RMSE) values also show that TOPO DEM has the lowest RMSE value (3.39 m3) compared to other DEMs. In general, it can be said that the use of TOPO DEM in Clark's IUH model will provide acceptable results.