A two-dimensional, time-dependent model of suspended sediment transport and bed reworking for continental shelves

A two-dimensional, time-dependent solution to the transport equation is for mulated to account for advection and diffusion of sediment suspended in the bottom boundary layer of continental shelves. This model utilizes a semiim plicit, upwind-differencing scheme to solve the advection-diffusion equatio n across a two-dimensional transect that is configured so that one dimensio n is the vertical, and the other is a horizontal dimension usually aligned perpendicular to shelf bathymetry. The model calculates suspended sediment concentration and flux; and requires as input wave properties, current velo cities, sediment size distributions, and hydrodynamic sediment properties. From the: calculated two-dimensional suspended sediment fluxes, we quantify the redistribution of shelf sediment, bed erosion, and deposition for seve ral sediment sizes during resuspension events. The two-dimensional, time-de pendent approach directly accounts fur cross-shelf gradients in bed shear s tress and sediment properties, as well as transport that occurs before stea dy-state suspended sediment concentrations have been attained. By including the vertical dimension in the calculations, we avoid depth-averaging suspe nded sediment concentrations and fluxes, and directly account for differenc es in transport rates and directions for fine and coarse sediment in the bo ttom boundary layer. A flux condition is used as the bottom boundary condit ion for the transport equation in order to capture time-dependence of the s uspended sediment field. Model calculations demonstrate the significance of both time-dependent and spatial terms on transport and depositional patter ns on continental shelves. (C) 2001 Elsevier Science Ltd. All rights reserv ed.