Practical 2DV Modeling of Deposition and Erosion of Sand and Mud in Dredged Channels due to Currents and Waves

Abstract

This paper presents an easy to operate time-dependent, two-dimensional vertical model for the simulation of sand and mud concentrations, transport, and morphodynamic bed evolution in conditions with combined currents and waves. The basic model equation is the advection–diffusion equation for sediments including flow velocities, sediment mixing coefficients, and the settling velocity. The vertical distribution of the sediment mixing coefficient is described by fairly simple and flexible expressions based on flow and wave parameters with user-specified coefficients for calibration of results. The settling velocity is constant or dependent on the sediment concentration to represent mud flocculation and hindered settling processes based on input parameters. The bed boundary condition is modeled by a bed concentration as a function of the bed-shear stress due to currents and waves. The model is valid for sand concentrations and for low and high mud concentrations including fluid mud concentrations. The numerical SUSTIM2DV model has been used to simulate sand and mud transport and bed level changes in dredged (shipping) channels. The model is valid for perpendicular and oblique flow across a dredged channel. The channel slopes should not be too steep (1V:7H or milder), because logarithmic velocity profiles are used. Results of various validation cases of channel deposition of sand, silt, and (fluid) mud in tidal conditions with and without waves are presented. The effect of channel geometry is specifically addressed. The numerical model has also been used to derive sediment trapping factors, which can be used in simpler channel deposition models.