二瀬ダム下流の粗粒化河道におけるダム還元土砂の動態評価

抄録

For improving river environment, artificial sand supply is recently conducted in downstream of dam reservoirs. However, there are many unknowns regarding how the sediment supply affects the bed material size and its dynamics at a flood event. Therefore, the purpose of this study is to clarify quantitatively the dynamics of artificial supplied sand in armored bed by proposing new model for calculating bed shear stress in the cobble layer. Quasi-three dimensional model has been developed considering the sheltering effect by boulders and decrease of bed shear stress. 2D model and the quasi 3D model are compared at flood events in downstream of the Futase Dam. Dynamics of sedimentation height and the deposited mean diameter were analyzed in the simulation. The quasi 3D model can express well the sedimentation at an inner side of meandering part of the river. The size of deposited material in gravel layer is more than 4cm. The model has a possibility to express the dynamics of supplied sediment motion in armored rivers.