Numerical Modeling of Restoration Alternatives in an Erosional Estuary

A hydrodynamic model coupled with an empirical erosion rate relationship is used to evaluate proposed restoration alternatives to mitigate erosion in an estuary. Because of land-use changes over the last 150 years, particularly the creation of a jettied harbor at the estuary's mouth, the estuary is rapidly eroding along its main channel and also losing vegetated marshplain habitat. In addition to the baseline option of taking no action, three restoration alternatives have been proposed to mitigate erosion in the estuary by reducing tidal exchange. To evaluate the impact of these alternatives on tidal flow, the estuary was modeled with a depth-averaged hydrodynamic model to provide water level, velocity, and bed shear stress predictions. The modeled bed shear stress also served as the independent variable for an empirical erosion rate relationship based on bathymetric surveys of the main channel. The hydrodynamic model and erosion rate relationship are combined to predict morphologic change after ten years for each restoration alternative.