[A-HW31] Water Environment and Geology in Urban Areas

[AHW31-P06] Exploring comprehensive watershed planning and management utilizing the natural topography in depopulated areas

*Ryuto Ugajin¹, Yoshiyuki Yokoo¹ (1.Fukushima University)

Keywords:Flood control, Adaptation strategy, Flood plain

We explore how to protect assets in depopulation areas with reduced investment for watershed flood controls. In such areas, it becomes harder to maintain rivers, making it difficult to safely handle extreme runoff. Climate change is making floods more severe and it is increasing the risk of flood disasters. To address this, we examine the benefits of combining two strategies: (1) relocating flood-prone areas, and (2) using natural topography to buffer runoff by reducing the river levees. As the result, we found we should relocate areas that are at risk of flooding under present conditions if we can continuously take the current river maintenance strategy. We also found that we should relocate areas under the risk of higher inundation damages, if we can use the natural topography to buffer runoff instead of the river levees. In addition, we found that this approach helps to lower and delay peak flows while reducing the risk of sudden levee failures. These results suggest that we should adopt a comprehensive watershed planning that combines relocation of our assets and buffering effects of natural topography, if we cannot continue our current infrastructure investments.