Simulation of Rainfall-Runoff Process and Estimate of Flood with HEC-HMSModel in Khorramabad Catchment Area

The rainfall-runoff process of a catchment area is mainly influenced by hydrological, Geomorphological and climatic conditions of the region. ne of the most popular methods for understanding the rainfall runoff process is its simulation by using the hydrological model and analyzing the results. In this study, by using HEC– HMS model, the rainfall – runoff of Khorramabad catchment area was simulated and analyzed. The results showed a good correlation between the observed and simulated Hyetographs at the basin outlet. The values of performance indicators which simulated at the validation stage by Nash–Sutcliffe coefficient and coefficient of variance were 0.68 and 0.09 respectively, which indicate the high-performance of model in estimating maximum flow in the studied catchment area. Then by using the optimized parameters, the rainfall Hyetograph at different return periods were entered in the model and the flood Hyetograph was obtained at different return periods. The use of model in the return periods of 2, 5, 10, 50, 100 years respectively has caused the flood peak discharge rate of 762, 1020, 1442, 1955, 2248 cubic meters per second. Results show that runoff can be predicted with high accuracy by using this model.