Abstarct: The increase of urban and rural development causes various constructions and human manipulations to be accepted in the boundaries of permanent and seasonal rivers, which causes the hydrological and hydraulic behavior of natural basins to be abnormal and irregular. In this research, by using HEC-HMS and HEC-RAS software and using GIS system, the two dimensional zoning of flow at the lower part of the karde dam was dealt with in two way by considering the dam’s structure and without considering it. In order to zone the two dimensional flow, the hydrograph of precipitation in 10, 25, 50, 100 and 200 years to calculate the discharge hydrograph with different periods with the hydrological finding process in HEC-HMS for the study area. For trending considering the dam structure, the trending of the dam reservoir is needed, which is provided by using HEC-HMS software capabilities. The results showed that the combination of HEC-HMS and HEC-RAS software is suitable for flood simulation. The peak discharge for the period of different returns for the case without considering the dam structure is respectively 36, 38/5, 64/5, 75/2 and 86/7 cubic meters per second and the area of flood zones in this case is respectively 102.05 102/19, 101/76, 106/35 and 108/54 hectares. Considering the structure of the peak discharge dam in the period of different returns respectively 9/6, 11/8, 19/2, 22/1 and 25/2 cubic meters per second and the area of floodplains respectively 69/20, 70/23, 70/37, 72/10 and 72/36 hectares. Taking the dam structure into account, the peak flow rate decreases by about 70 percent compared to before the construction of the dam structure, but the flood zones with different return periods decreased by about 31 percent. Using the DSISR method, 15/5 meters is suggested for the privacy limit on the left and right coasts. According to the flow lines in the flood zones in order to control the flood in the places where there is a possibility of damage, suggestions were given to increase the depth, widen the bed and improve the communication roads.