عنوان مقاله [English]
Catchment as a Hydrosystem that react toward inputing rain. This reaction shown in dimention of the flood hydrograph. In this study, first using a combination of maps, land use and soil hydrologic group in ARC GIS, map of curve number was obtained for basin then Using HEC- geoHMS extention basin model was prepared. Finally, for estimate the height of the runoff and study the status of flooding and hydrological of Ghouchak - Roodak watershed, HEC- HMS model was implemented. In order to validate the model, five incident rainfall - runoff extract from Roodak hydrographic station and after modeling, estimation flow rate were compared with observation flow rate. results model in connection with the performance of the model in runoff and flood peak is not acceptable. Because the difference between the observation and estimation peak flow is over twenty percent.