Simulation of hydrograph of flood with hydrological model HEC-HMS and prediction of return period in Kermanshah Ravansar Basin

Abstract

The data and information was gathered from the meteorological and hydrological stations of Ravansar watershed during a period of 18 years. Then, with help of Hyfa software the recurring preiod of the momentary maximum flood discharge was calcuated. For modeling, five events of rainfall-runoff was selected. In the process of calculation of the modle to calculate the runoff loss, SCS network; to convert the process of execessive rainfall to the surfaceflow, SCS hydrography unit; and for flood routing in different part, of the rive, Muskingum hydrologic routing were utilized. Analizing the results, it was found that there is significant different between the computational and observational data. Hence, the modle was calibrated. After calibration, the result showed a reduction of difference between the computational and observational data. To verify these result, the model was validdated through using three new rainfall-runoff events. The obtained validation results confirmed the accuracy of the calibrated parameters. The results of this study indicate the capability of HEC-HMS model in simulating the hydrologic behaviors of Ravansar watershed. This modle has a performance capability with a mean error of 0/7 % estimating the peak discharge and a mean error of -3/33 % in calculating the flood through using Hyfa software, the maximum flood discharges were calculated in periods of 2 to 500 years. After reviewing the results, the percentage probability of error prediction in recurrent two year periods was the least and as the length of recurring preiods increased, the percentage of errors increased as weel

Keywords

• flood precipitation-runoff. prediction
• hyfa
• hec-hms