Determination of the Return Period for Probability Maximum Flood Using HEC-HMS Model and Statistical Methods in the Eskandari Watershed

In this study, Probable Maximum Precipitation (PMP) and the corresponding return period were estimated. Then HEC-HMS model was calibrated to estimate the characteristics of the PMF in the Eskandari watershed, branch of Zayandehroud River. Firstly, using Hirschfield method and statistical distribution, maximum 24-hour rainfall amounts in different return periods were determined as well as PMP. Then, the next step by using two events with the best model efficiency coefficient, HEC-HMS model calibrated and then the model evaluated by two various other events and was obtained acceptable results. Also, the estimation of PMF characteristics showed that precipitation of 240.6 mm and 596374 year return period can generate flood peak of 3079.5 m3/s and volume of 178.1 Mm3.