In order to develop a science-based method to design the optimal flood control operation of reservoirs during extreme flood events that may increase under the changing climate, a method is proposed for optimization of reservoir's flood control operation based on inundation analysis in the downstream. At first, rainfall scenarios are developed for extreme flood events. Multiple patterns of rainfall scenarios with different scale and spatiotemporal distribution are considered to take different

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... terns of runoff into account. River discharge, inundation area and depth in the target river basin are then estimated for the rainfall scenarios using the RRI model, a rainfall-runoff-inundation model. Optimal reservoir operation for flood control is analyzed from results of the inundation analysis of the considered extreme flood scenarios. The proposed method was applied to the Hiyoshi Reservoir in the Upper Katsura River in Japan, and optimal flood control strategy of the reservoir was respectively identified for each scenario of extreme flood event.