A New Approach on Unit Flood Response Method in Prioritization of Sub-basins for Flood Control Activities

Due to increasing rate of flood risk throughout the world, including Iran, it is necessary to identify and prioritize flood-contributing areas for flood control activities. In this study, a new approach on Unit Flood Response method called “Flood Reduction method” was introduced which is applicable to prioritization of sub-basins for flood control activities. It was used to prioritize upstream sub-basins of Kardeh dam in Khorasan Razavi province. To conduct the study, the entire basin was divided into 24 sub-basins and physical characteristics of the basin and sub-basins were extracted using HEC-GeoHMS extension in ArcGIS. HEC-HMS model was calibrated using a rainfall-runoff event data and then, the 50-year design storm was simulated by this calibrated model. Prioritization of flood source areas was performed using the Unit Flood Response method and the Flood Reduction method was used to prioritize flood control activities. For the basin under study, the results showed that the sub-basin which has higher flood contribution is not necessarily the most appropriate sub-basins for flood control activities. In general, the prioritization results of the Flood Reduction method and those of the Unit Flood Response method were significantly different. The effect of rainfall duration on sub-basins prioritization was also studied. The results showed that rainfall duration has a significant effect on the sub-basins prioritization.