Author(s): M. Iwamoto; D. Nohara; Y. Takemon; T. Koshiba; T. Sumi
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Keywords: Reservoir operation; Flood control; Inundation analysis; RRI model; Extreme events
Abstract: Heavy rainfalls have frequently caused severe flood disasters in Japan. In order to mitigate inundation in the downstream reaches, it is important to effectively operate upstream reservoirs for flood control. The flow capacity of downstream rivers is often insufficient when the progress of river improvement works is behind schedule. In such cases, flood control rules at some of the upstream reservoirs have been changed in order to address small or medium floods that occur more frequently: the release discharge rate are se t to smaller values than that originally designed. During large floods, however, the water level of such reservoirs could rapidly increase and, due to their restricted release rate, reach the full storage level. This situation puts the reservoirs in the danger of losing their flood control function. In order to overcome this situation, in this study, effectiveness of flood control policies were assessed considering varied flood scenarios. Reservoir states, river discharge, and inundation depth and area in the downstream were calculated by rainfall-runoff-inundation (RRI) model for rainfall scenarios with different scale and spatio-temporal distribution, changing flood control policies of the reservoir. Through the case study with the Hiyoshi Reservoir in the Katsura River, Japan, optimal reservoir flood control policy was identified so as to minimize the potential economic losses estimated by the simulated inundation depth and area.
Year: 2020