Morphodynamics of Sandbar in a Macro-tidal Estuary: A Model Approach

This paper studied the development and the underlying physical mechanisms of the large sandbar in Qiantang estuary, China, using an idealized morphodynamic model. The model coupled shallow water equations, cohesive sediment transport and bed level update equations. The model was given a fixed geometry and impermeable boundaries, and forced by M2 tide at mouth and river discharge at the upstream. The sandbar was reproduced on a timescale of 30 years, and the spatial scales of the sandbar were comparable to the real situation. The formation of the sandbar was controlled by the flood dominance due to tide wave deformation and sufficient sediment supply. The morphological development was driven by the nonlinear interaction between hydrodynamics, sediment transport and bed evolution. This morphodynamic model provides a new tool for the analysis of the large-scale morphological behaviour of tidal sandbar.