Efficiency Comparison HEC-1 and TR-20 Methods in Flood Hydrograph Simulation

Flood is one of natural disasters worldwide that can cause loss of life and great economic damages. Hence, simulation of hydrological processes such as rainfall-runoff occurred in watersheds is of importance.In the present study, two methods were applied to simulate the floods process the Kameh Watershed located in northeast Iran, including HEC-1 and TR-20methods.The HEC-1 and TR-20 models were run within the WMS environment. In addition, an attempt has been made to compare the performance of the HEC-1 and TR-20 methods and validate the models with recorded data from the watershed. After preparing topographic maps with 1/25000 scale in ARCGIS9.3 software environment and a digital elevation model (DEM) and its correction in WMS environment by using the TOPAZ model, streams and river network was drawn and then, by determining the outlets location, the boundaries of the watershed and sub-watersheds were specified and the physiographic characteristics of the watershed were calculated. Finally, by using the HEC-1 and TR-20 models, rainfall–runoff simulation was performed to estimate peak discharges and runoff hydrographs. In the research, three criteria, namely, Nash-Sutcliffe (NS), Deviation Volumes (DV) and Peak Error Percent (PEP) were used to compare the performance of the models.Among the two methods used to estimate the peak discharges (the TR-20 model and the HEC-1 model), the HEC-1 model can be concluded as the better option both in terms of hydrology and computer advancement. HEC-1 model provides further accuracy for the simulation and validation of rainfall-runoffprocesses when gaged precipitation and runoff data are available. With respect toHEC-1 model processesaren’t easily available; hence, TR-20 model for many similar and ungagged basins can also be used.Sensitivity analysis shows that parameters of channel roughness coefficient and minimum slope threshold have more influence than parameter of threshold of drainage area in delineating channel networks on peak discharge, time to peak and hydrograph shape.