洪水撹乱誘発に対する中州掘削と河床材料の効果

摘要

Recently, riparian trees in the course of gravel-bed rivers have been very much increasing, while gravel beach without vegetation has been very much decreasing. This study aims to propose effective measures for reproducing gravel bars by leading flood flow over vegetated bars. The bed excavation over the vegetated gravel bar in the segment-1 zone of Watarase River was conducted for the management of riverine trees and the recovery of gravel bars with geomorphic changes caused by flood disturbance. After a flood on September 2007, an significant bed variation was caused in the excavated area which made a secondary channel due to active sediment transport by flood flow. As results of the field survey and the numerical study, it was confirmed that the bed excavation was effective in the riverbed deformation and the management of gravel-bed river. In addition, the importance of riverbed materials in the riverbed deformation was shown.