Ecology, Environment and Conservation Paper

CALIBRATION, VERIFICATION, SENSITIVITY AND ESTIMATING FLOOD SPECIFICATIONS IN DIFFERENT RETURN PERIODS USING HEC-HMS HYDROLOGIC MODEL (STUDY AREA: GHAREH AGHAJ BASIN, IRAN), IRAN

Ebrahim Afiat Doust , Amirpouya Sarraf and Fardin Boustani

Abstract

Human life on the earth leads to great changes on the earth surface that it has important role on causing flood on that area. Using method or methods for estimating that rate of run-off from rain in basin without statistic or with deficient statistic is very important, with consider to available conditions most complexity of hydrological systems and lack of perfect recognition. Now, there are different models for the simulating conversion of rain to run off. HEC – HMS model is one of them. In this study after collecting data and information, morph metric characteristic of basin is investigated with using digital elevation maps, information of measuring rain stations, measuring water, soil and dominant vegetation on that area. Simulating raining – run off is done and resulting hydrograph after calibration evaluated, with available information of measuring rain stations, measuring water and using HEC – HMS model. Calibration steps and model evaluation is done using observation 5 storm with simultaneous storm water. Final results show the error of discharge estimating and runoff volumes in output of “Tangehkarzin” basins with observed amount are 7.5 and 21 percent, respectively also, the amount of model error in estimating the time of discharge occurrence in output at one hour of basin or with consider the time of storm water starting were 6.25 percent. After that it is confirmed by model, flood hydrograph simulated for different return periods and for every maximum probable rain and raining. Analysis results were sensitive to estimating the max of discharge and also storm water volume. The model sensitivity in front of CN changes has a direct relation with initial infiltration and delay time. In estimating observation time of basin. In investigating the flood intension it is cleared that forming maximum discharge in Gharehaghaj basin, middle basin has a more share on it, if potential flood producing is investigated with consider to every square of under basin in forming maximum discharge. It is recognized in surface unit, middle sub basin are better for producing run-off.