Using a numerical model with moving boundary conditions to study the bed change of a Mekong river segment in Tan Chau, An Giang, Vietnam

Abstract

Numerical models that calculate bed change are becoming increasingly popular because of their longterm forecast projections and their ability to identify causes of bed change. However, the reliability of the simulation results depends on the length of the data series and the algorithms in the model, in which the boundary condition method plays a critical role. The aim of this study is to assess the effectiveness of the HYDIST model to update wet and dry fronts as well as recalculate the wet boundaries of the hydraulic model before its input into the sediment transport model. The moving boundary theories (wet and dry fronts) of Zhao (1994) and Sleigh (1998) were applied. The velocity distribution of the wet boundaries was recalculated after every time step, then the outcomes of the hydraulic model were used as input for the sediment transport model. The results showed good agreement between the simulated and measured data in term of discharge, water level, and sediment concentration. At the same time, the HYDIST model can be successfully used to simulate sediment deposition and riverbank movement.

Keywords

• bed change
• boundary condition
• Mekong
• numerical model
• sediment transport