Multi-layer modeling of three-dimensional hydrodynamic transport processes

A multi-layer water-sediment predictive model has been developed to study the effects of coastline reconfigurations on the three-dimensional (3-D) flow and sediment fields in coastal waters. The model is gridded with finite elements in the horizontal domain for easy adaptation to complex boundary configurations. The non-uniformity of flow and sediment distributions in the water column are represented by multiple vertically averaged layers. The Lax-Wendroff two-step scheme is used for time marching. This allows the flow field and sediment field to be explicitly coupled so that the density of the water-sediment mixture and the flow depth are updated without matrix inversion for the advanced time level. Because of the adoption of the explicit time-marching scheme, the allowed time increment of the present numerical scheme is relatively small. However, this is beneficial to studying short life activities such as sediment entrainment and deposition. The model predicted results were tested against field measurements in two case studies and good agreement was found in each case.