Evaluation and Analysis of Peak Discharge with Different Return Periods for Beshar River Using HEC-HMS Model

Flood is one of the most important natural disaster that cause human and financial damages and its evaluation needs peak discharge. This study evaluates Beshar River runoff peak discharge due to precipitation with different return periods. The geological and land use maps were provided in ArcGIS and ENVI, based on which the CN map was prepared. Respectively, 53.46 % and 30.75 % of the study area are in A and D hydrologic groups. The best probability distribution for each station was determined using Chi-square test, thereafter, precipitation with different return periods was calculated. After dividing the area into 9 sub-basins and calculating the required parameters for each, the model was created. Three and two flood events were respectively used for calibration and validation and the average values of RMSE and NS indexes were obtained as 0.53 and 0.67 for calibration and 0.55 and 0.68 for validation. The low values of errors indicated the reliability of the simulated model. The peak discharge of each return period was calculated employing type IA of SCS model. Comparing the peak discharges obtained from HEC-HMS and statistical method at the basin outlet showed that the least difference between these two methods was related to the 50-year return period and for the return periods below and above 50 years, the HEC-HMS discharges were correspondingly less and greater than the statistically calculated peak discharges. Consequently, the HEC-HMS model can accurately calculate the flood peak discharge for Beshar basin.