Study on river change and sediment transportation of Tan Chau reach in lower Mekong river

摘要

This study presents field data of topography change, bed material, water surface elevation and hydrograph at Tan Chau reach in Vietnam to understand mechanism of the river change. The results of field survey show that bank shifting tends to occur toward anti-clock wise and sand bars migrate downstream, resulting in a much larger bar, which is influenced by co-presence of non-cohesive and cohesive sediment and artificial works. In addition, bed material loads are originated by bank erosion. A two dimensional numerical model is proposed to simulate flow pattern and associated river change. In this model, erosion rate formula for cohesive material and formula for estimating the thickness of sediment transport layer as a function of bed shear stress are introduced into the standard layer model which was firstly proposed by Hirano (1971). The proposed model can estimate the sediment transport rate on the bed composed of non-cohesive and cohesive material and predict the topography change of study reach.