Evaluation of Climate Change Impacts and Adaptation Measures on Flood Inundation Risk based on Levee Breach Potential of Rivers in Japan

Abstract Submission: In recent years, the scale and frequency of torrential rains and flood inundation have been increasing due to global warming. It is important to enhance flood hazard information, such as multi-level flood risk information, in addition to existing hazard maps. Also, a current issue with hazard maps in Japan is the lack of consideration for levee erosion risks in steep rivers. In Toyama Prefecture, there are world-famous steep rivers, including the Kurobe River and Joganji River, which have a risk of levee breach due to erosions. To promote resident evacuation, it is necessary to provide hazard information that considers the erosion risk of levees. The purpose of this study is to evaluate the climate change impact on the flood risk considering the levee breach potential and several counter measures at the several river basins in Japan.
The rainfall runoff and flood inundation simulations considering the climate change impacts were conducted at the Kurobe and Joganji Rivers in Toyama Prefecture, Japan. For the climate change analysis, d4PDF (database for Policy Decision making for Future climate change) were utilized in this study. Especially in this study, the flood inundation probability at each grid was calculated based on the risk of levees erosion potential. This flood inundation probability will be used to support local residents to recognize the risk of their own residential areas and to promote evacuations for the flood disaster mitigation.
The results of the analysis show that the probability of inundation in the inner area of the levee, the probability of inundation above floor level, and the probability that horizontal evacuation was affected by the erosion potential of the levees and climate change impacts. In addition, we evaluated the several counter measures such as vegetation management of rivers to mitigate these flood risks associated with the levee breach potentials.

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