The Computational Analysis of Flow and Sediment Transport in Lower Reach of Chikugo River, Japan for a Quantitative Evaluation of Wakatsu Port Training Levee

Yuki Koga, K. Ohgushi

Tuesday 30 june 2015

12:54 - 12:57h at Mississippi (level 1)

Themes: (T) Sediment management and morphodynamics, (ST) Sediment transport mechanisms and modelling, Poster pitches

Parallel session: Poster pitches: 5A. Sediment - Erosion

The lower reach of Chikugo River, Japan is greatly influenced by tide because this river flowing into the Ariake Sea which has the largest tidal range in Japan. Tidal currents transport a large amount of mud and muck sediment tends to deposit on the middle stream and the lower reach of the Chikugo River. In 1890, Wakatsu Port Training levee has been constructed for the purpose of preventing the deposition of sediment and securing the route. More than 120 years has elapsed but an initial purpose of this training levee has been maintained. In 2008, this training levee was selected as the recommended civil engineering heritage. However, there is few study about evaluation of this training levee. This study has a quantitative evaluation of the functions of Wakatsu Port training levee in the lower reach of Chikugo River. Numerical simulations of flow and sediment transport in the lower reach of Chikugo River are implemented. 1-D 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 the 3-D diffusion equation for the sediment. As a result of 3D flow simulation, it becomes apparent that the existence of training levee causes to accelerate the flow of left bank side of the river. The sediment transport analysis gave understanding of the deposition conditions of the deposition by comparing the river bed variation distribution map or the transition.