確率的アプローチによる高水敷保護工施工範囲の設定

抄録

Determining the protection area of river floodplain against the erosion during large flood is a major concern in river management works. In general, some threshold values of hydraulic parameters (e.g., water depth, velocity) have been used to identify potential zones of significant floodplain erosion, but, such approach does not perfectly explain the observed floodplain erosion area. Here, we propose a simple probabilistic approach for better decision making of floodplain protection. As a case study, we focuse on the floodplain erosion caused by the record-breaking flood event in the Bebetsu River, Hokkaido, Japan observed in 2016. The probabilistic distribution of several hydraulic parameters, which are estimated by a numerical simulation, are compared with the observed erosion area. We find that the distribution of shear velocity is well linked to the probabilistic distribution of the floodplain erosion. The proposed approach might be more flexible tool to decide the protection area of floodplain.