Author(s): Y. Koga; K. Ohgushi; T. Jansen
Linked Author(s): Koichiro Ohgushi
Keywords: The lower reach of Chikugo River; Wakatsu Port training levee; Quasi 3D numerical simulation; Suspended load; Sediment transport
Abstract: This study has a quantitative evaluation on the functions of Wakatsu Port training levee in the lower reach of Chikugo River, Japan. Numerical simulations of flow and sediment transport in this lower reach of Chikugo River are implemented. A 1D unsteady flow numerical simulation is executed to obtain the boundary conditions for a quasi-3D unsteady flow model which is used to simulate the detailed flow features around the training levee. The movement of sediment in the water is simulated by solving a 3D diffusion equation for the sediment. As a result of the 3D flow simulation, it becomes apparent that the existence of training levee causes to accelerate the flow of left bank side of the river against maximum flow velocity during the flood. From the results of sediment transport analysis, it found that the both cases of river beds show tendency of erosion regardless of the existence of the training levee by comparing the river bed variation distribution. Large river bed variations in the upstream and midstream can be seen, especially, in the left bank side for the case with the training levee. By comparing the river bed variations between the case with the training levee and the one without it, the transported sediment eroded in the upstream reach is considered to be transported downstream and have been deposited at the midstr eam reach where the flow velocity has decreased after the training levee’s construction.
Year: 2015