Prediction of Wind Waves in a Shallow Estuary

Abstract

In comparison with wave modeling on an open coast, the complex geometry and bathymetry of estuaries, the unsteady conditions associated with estuarine circulation generated by tides and winds, and the relatively inadequate field data present a unique challenge. This study utilizes an unsteady, curvilinear spectral wave model that has the flexibility to resolve large geometric and bathymetric gradients and allows for consideration of unsteady forcing and currents to predict wind waves in Mobile Bay, Alabama. First, a laboratory data set on wave transformation over a circular shoal is chosen to test the curvilinear wave model. Excellent agreement is found between the numerical results and the laboratory measurements with a directional wave input and fine spatial resolution. Second, a three-dimensional circulation model is used to predict the varying current field and water levels that serve as the input to the wave model. The predictions of the wave model under unsteady forcing and ambient currents are then compared with the existing field measurement of wind waves in Mobile Bay. Numerical experiments are carried out to examine the effects of estuarine circulation and grid resolution on the model result. The study shows that the technique of linking a spectral wave model to a hydrodynamic model on curvilinear grids is an effective tool for wave prediction in estuaries.