Modeling the effect of wind-waves on the evolution of marshplains and mudflats

A one-dimensional sediment and bed model was constructed to assess the long-term evolution of shallow intertidal zones. Observations indicate that shallow intertidal basins tend to be characterized by a bimodal distribution of water depths into higher marshplain and lower mudflats. The model is used to investigate the mechanisms and factors affecting the transition of a shallow coastal region into either a marshplain accreting to mean high-high water level, or eroding into mudflat. Wind waves and tidal currents both affect the deposition and erosion of sediments. For two weeks, field data was collected at a tidal wetlands restoration site in San Francisco Bay, California to provide a comparison with model results. Two locations within the field site with different wind climates are compared to show the impact of wind on the accretion rate. Model sensitivity is tested for parameters, such as the fetch length, initial marsh elevation, and mass flux of sediment, to study their relative importance to accretion. The model provides a tool in engineering and design applications in developing strategies for restoring or protecting existing tidal marshes.