In this study, which located in the province of Mugla and covers the applied hydrography features Namnam River Basin, which covers 543.66 km(2). The study area has a very rugged topography with elevation to 2295 meters from the shores of the Koycegiz Lake. Has been an important activity in a variety of surface shapes of erosion and deposition of river activities. In this study, we have examined the factors affecting general hydrography of the applied field and the field of flood risk characteristics have been determined In addition, flood frequency analysis using maximum flow rate of the different years in terms of probability of occurrence of floods have been identified. Ongoing and planned construction of the places mentioned in the selection of properties were informed about the water holding capacity of the dam and made space volume calculations.