A comprehensive model of Coastall currents and sediment dispersion has been formulated and applied to the Mississippi Sound and adjacent continental shelf waters. The study combines mathematical modeling of various hydrodynamic and sedimentary processes with laboratory and field experiments. Of primary importance is the development of an efficient and comprehensive three-dimensional, finite-difference model of Coastal, Estuarine, and Lake Currents (CELC3D). The model resolves currents driven by tide, wind, and density gradient. It has been applied to the Mississippi Sound, and results agree well with measured surface displacements and currents during two episodes. Rates of entrainment and deposition of the Mississippi Sound sediments have been studied in a laboratory flume. Effects of (1) bottom shear stress, (2) bed properties, (3) salinity of water, and (4) sediment type on the erodability of sediments have been examined. Results of the laboratory study have been incorporated into the bottom boundary conditions for a three-dimensional sediment dispersion model. Gravitational settling and particle size distribution of the Mississippi Sound sediments were also studied in laboratories. Bottom boundary layer dynamics and wave effect on sediment dispersion have been studied by means of a turbulent transport model and a wave model. Model simulations of sediment dispersion in the Mississippi Sound agree well available data from ship surveys. (Author).

This report documents the use of the CELC3D computer code for the computation of two- or three-dimensional unsteady currents in coastal, estuarine, or lake waters based on the free-surface model described in detail by Sheng. The present version of the code is implemented on a VAX 11/780, a virtual machine. It therefore contains no buffering scheme and is programmed to run entirely in the central memory. Since it has no buffering scheme, it contains no machine dependent input/output and, except for minor program changes, should run on any other virtual machine, e.g., the CDC cyber 203, or other non-virtual machine with sufficient memory. The CELC3D program solves the mean equations of fluid motion within a water body with respect to a right-handed Cartesian coordinate system located at the nominal water surface. These equations consist of the partial differential equations for surface displacement, vertically integrated velocities, three-dimensional velocities, temperature, salinity, density, and sediment concentration. The equations of motion are solved in dimensionless forms and are given in Appendix A in detail. The major variables and their corresponding FORTRAN names are given in Appendix B. Sheng presented numerous example calculations of the CELC3D model, including: tidal currents in an open bight, wind-driven currents in a shallow lake, wind-driven currents in an open channel, formation and deepening of a thermocline, and tide- and wind-driven currents in the Mississippi coastal waters, etc. This report, for simplicity, only briefly presents the application to Mississippi coastal waters.