中山間地河川の部分拡幅部における被災分析と軽減手法および環境評価に関する事例研究

抄録

"Local River Widening (LRW)" is one of a potential option in small-middle rivers on valley plains and fluvial fans for preventing hazardous sediment and woody debris and creating environment diversity in the same time. However, the effects and proper management have not been sufficiently studied. In the study, we discussed subjects for application of the LRW method by applying 2-dimensional morpho-dynamic simulation model to a pilot site in the steep stream which damaged by flood disaster after construction. The simulation showed water surface significantly destabilized with occurring hydraulic jump in case of under supercritical flow condition. As found in the field, bedload was deposited in the stream part, not in the local widening part. Smoothing of the outlet of is an effective countermeasure to stabilize the water surface and the river bed behavior. The environmental evaluation linked to the morpho-dynamic simulation provides useful results for decision making.