A new approach to model sediment resuspension in tidal estuaries
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A new scheme to model surface erosion of bottom sediment in tidal estuaries is demonstrated in this paper. The erosion or resuspension scheme used accounts for the sediment deposition and erosion history based on an empirical formulation, which relates critical shear stress for erosion (c) to accumulated eroded mass. A point model, which does not consider advection and diffusion, is built to test the scheme and explore the parameters involved. The results show that sediment concentration reaches 10 mg l-1 with an amplitude of tidal current 0.15 m s-1, and 34 mg l-1 with an amplitude of tidal current 0.30 m s-1 in a 2.5 m water depth. Such values are representative in shallow areas of Baltimore Harbor where the empirical equation was obtained. Compared to the traditional way of using a constant c in a sediment transport model, this scheme allows sediment resuspension to occur at places where bed shear stress is low, since as long as there is freshly deposited materials at the bed, erosion starts at low critical shear stress. The scheme is then incorporated into a three-dimensional numerical sediment transport model. The magnitude of simulated sediment concentrations agrees well with the observation data.