A sediment transport model is being developed for the dispersion and transport of suspended sediment in the benthic boundary layer on the continental shelf. The model is one component of an impacts zone assessment model for drilling discharges on benthic organisms such as the sea scallop on Georges Bank. A key feature of the model is the simplified representation of vertical mixing through the random shuffling of packets of material and the use of observational suspended sediment profiles as probability density functions for the overall vertical distribution. Horizontal transport is then represented through advection of the packets in vertically- and time-varying flow fields.
The dominant dispersion process acting in the model is horizontal shear dispersion -- due to the interaction of vertical mixing and vertical shear in the horizontal currents. The effective horizontal dispersion rates in the model are consistent with the fundamental idea that shear dispersion is linearly proportional to the product of the vertical mixing time scale and the mean square velocity deviations experienced by the suspended sediment.
This talk will concentrate on the model's representation of shear dispersion and comparison with analytical solutions. Applications to a drilling site on Sable Island Bank and to the scallop grounds on Georges Bank will also be discussed.