Adaptation of a state-of-the-art three-dimensional hydrodynamic model to Mobile Bay and surrounding coastal areas

This research deals with the adaptation and application of a three-dimensional hydrodynamic model to Mobile Bay and its surrounding coastal areas. The goal is to identify those variables controlling the currents within the bay and how they may influence the transport of sediments suspended in the water column. The selection of the model is made taking into consideration typical characteristics of the bay area. The main forces controlling the hydrodynamics of this system are tide, total river input into the bay, and direction and speed of wind. A historical literature search is performed to determine typical input ranges for each of these variables.;Test runs of the numerical model are performed to determine its sensitivity to tide, combined river flow and wind. From the results, three levels of tide and three levels of total river input are defined to perform a total of nine simulations of the bay. The three-dimensional hydrodynamic output data is processed for each of the nine simulation cases to create animations that display the conditions of the bay throughout full tidal cycles. This information graphically shows that tidal-driven currents flowing around Dauphin Island are affected by the high-energy pass exchange created by the presence of Main Pass. Thus, it is believed that the transport of suspended sediment along the coast of Dauphin Island can be statistically correlated to the energy of the currents flowing in the area.;To proceed with the analysis, the hydrodynamic data was processed to obtain the magnitudes of the average stresses along the coast of Dauphin Island that are produced by the nine events studied. The input variables (tide and combined river flow) were statistically analyzed to assign probabilities of occurrence to each of the nine events studied. The beachfront advance/recess at Dauphin Island was measured using topographical data from 1958 and 1982. Finally, a model was proposed to correlate beachfront advance/recess to the stress magnitude in each cell and the probability of occurrence of each simulated event.