Evaluating the HEC_HMS model for estimating flood hydrograph in Kasilian basin

Flood damage mitigation and control has a special place in integrated watershed management. There for the exact identify of flood ness areas is necessary. Because through suitable watershed measures include structural or nonstructural or a combination of both of them can be reduced flood ness of watershed. this research focused on a comparative of Synder، SCS unit hydrograph، and Clark methods in flood hydrograph estimation with attention to lower different percent between discharge observation and estimation and hydrographs investigation، SCS UH method has been chosen as the best one. In next step، the sensitivity analysis of model related to different parameters has been done. the results showed that the lag time factor is the most effective factors on the model. Finally the priority of the main sub basins of Kassilian watershed carried out by using HEC-HMS simulation model. In this research the 6 sub basin have been chosen by using of HEC GEO extension in ARC/VIEW software. By providing and reconstruction of requirement data and maps to model through geographic information system (GIS)، the curve number (CN) in loss part of model and Maskingham method for flood process have been chosen. In this study the sub basin number 4 has been identified as the flooding sub basin. Also results show that the amount of sub basins cooperation in the out let flood is not directly related to their areas