Floodplain Management by Geographic Information System

River floodplains are fertilized areas that are most considered by humans, and people always like to develop these areas. Therefore, the conservation and management of this area is most important. In This study for management purposes, the 4.5 Km of Ghezelozan River, was determined as flood hazard zone using HEC-RAS with ArcView andHEC-GeoRAS extension. In order to, do the research, digital maps in 1:1000 scale were provided and the area of study was classified to 118 cross sections. In the other side the hydrological information determined and the Manning roughness coefficient was estimatedusing Cawen Method. Finally the flood area and depth maps were provided for 7 different return periods of 2, 5, 10, 25, 50, 100 and 200 years. Results showed that about 86.14% of the flood prone area to flooding under 25y return period for 200 years. The flood depth maps indicated 57.29% from flood depth of 200 yreturn period belonged tothe to flooding under 25y return period.