Flood Generation Potential Analysis Based on Runoff Coeffiecient Map in Latyan Watershed

There are different factors affecting flood generation such as: intensity and amount of rainfall، basin slope، land permeability، topography، physiographic characteristics، vegetation cover and degree of soil saturation. Flood generation potential implies the basin capability in generating surface water runoff being transformed to flood flow. It is then assumed that main factors affecting flood generation potential are strongly associated with runoff coefficient values. It can be then said that runoff coefficient is the best measure to reflect the runoff generation potential of a land or the potential of flood flow generation at a basin. Runoff coefficient is the ratio of runoff generated to the rainfall received at a basin and its value varies between zero and one. In this study the flood generation potential of the Latyan watershed (Jajrood river basin) was analyzed using runoff coefficient. Using the GIS technique، the necessary and basic information in order to estimate runoff coefficient at the Latyan watershed were analyzed. The results showed that more than 91% of the study area has high slope resulting in the runoff coefficient potential of 0. 61 at the catchment scale. Maximum runoff coefficient of the study area with a value of 0. 89 is related to the residential areas، and the minimum runoff coefficient (0. 1) belongs to the forest land use.