四万十川と後川合流部における土砂堆積軽減策に関する研究

抄録

Recently, the lack of discharge capacity due to sediment deposition and reduction of crop yields of natural Enteromorpha prolifera become problems in from 5.0km to 6.0km from the Shimanto River estuary, confluence of the Ushiro River. In this study, to mitigate the sediment deposition around the confluence point, we proposed the river improvement method that can control the sediment deposition and maintain by experiments using the movable bed and two-dimensional riverbed variation analysis. Authors clarified that the cause of sediment deposition is the longitudinal and cross-sectional change of tractive force occurring under the condition of 3,500 m³/s by two-dimensional riverbed variation analysis. And it was confirmed that improving the shape of the guide wall at the confluence point can reduce the deposit accumulation.