Numerical Modeling of Suspended Sediment Transport Affected by Tidal Bore in Qiantang Estuary

Study of suspended sediment transport in an estuary affected by tidal bore is important for coastal engineering and management because the tidal bore can cause strong sediment resuspension and scour in shallow waters Numerical modeling of suspended sediment transport in a natural estuary affected by tidal bore is such a challenging research topic that there are few articles on the subject available in the literature In this study a two dimensional numerical model was developed to investigate suspended sediment transport induced by a tidal bore The hydrodynamic component of the model employs the Godunov type scheme with second order accuracy in space which effectively describes the rapid supercritical flow and sharp horizontal pressure gradients of the tidal bore To preserve balance between the source terms and the internal forces both the water level bottom topography formulation (WLTF) method and a special technique for triangular mesh have been applied to solve the source term in the model equations to account for the irregular bottom topography The wet/dry boundary issue was solved by using the improved exact Riemann solver on the dry bed The coupled sediment transport model incorporates more reliable equations from recent publications to characterize the rapid increase of sediment resuspension in the water column The model test against an analytical solution of convection transport shows that the sharp gradient of scalar transport is satisfactorily estimated in the model simulations The model in the application has been validated to simulate hydrodynamics and suspended sediment transport affected by a tidal bore in the Qiantang River of China The results compare well with a time series of observations to characterize the rapid increases of surface elevation currents and suspended sediment concentration resulting from the tidal bore Results of spatial distributions of water levels and currents indicate that the model adequately describes the sharp horizontal gradients of the surface elevation and the tidal currents during the passage of the tidal bore and characterizes the suspended concentrations in the estuary