Numerical modeling of cohesive sediment transport in a tidal bay with current velocity assimilation

Tidal currents play an important role in sediment dynamics in coastal and estuarine regions. The goal of this study is to investigate the effects of current velocity assimilation (CVA) on sediment transport modeling in tide-dominated waters. A hydrodynamic and sediment transport model for Deep Bay, Hong Kong, was established based on a three-dimensional primitive equation Finite Volume Coastal Ocean Model. An additional numerical simulation was conducted with in situ current velocity measurements sequentially assimilated into the model using a three-dimensional optimal interpolation scheme. The performance of CVA shows improvements in the root-mean-square errors and average cosine correlations of simulated current velocity by at least 9.1 % and 10.3 %, respectively. Moreover, the root-mean-square error of the simulated sediment concentration from the model with CVA was decreased by at least 7 %. A reasonable enhancement in the vertical and spatial distributions of sediment concentrations was demonstrated from the simulation results from the model with CVA. It was found that the bottom shear stress changed significantly when the simulated velocities were corrected with CVA. The results suggest that CVA has the potential to improve sediment transport prediction because tidal currents dominate sediment dynamics in the studied areas.