A numerical model for fine suspended sediment transport in the southwest lagoon of New Caledonia

A hydrodynamic-transport coupled model is used to understand the transport of fine suspended sediments in the southwest lagoon of New Caledonia. The hydrodynamic model is briefly presented and the circulation due to the tide and to averaged trade wind forcings is analyzed. The transport model for fine suspended sediment is described. Parameters involved in this model (settling velocity, critical shear stresses, erosion rate coefficient, Schmidt number) are discussed and a calibration procedure is proposed. Using the resultant parameters, the erosion and deposition areas predicted by the sediment-transport model are in very good agreement with the distribution of the percentage of mud at the seabed. The sensitivity of the model to the different sedimentary parameters is studied, and the influences of the tide and wind on deposition and erosion are discussed. The influence of the wind is dominant in seabed exchange processes in shallow areas and produces large erosion rates where the water depth is less than 20 m. The tide controls the particulate transport, vertical mixing, and deposition rates in the areas where the influence of the wind is weak.