A numerical model was developed for the Mobile Bay system to investigate the impacts associated with certain system alterations. The Adaptive Hydraulics (AdH) Code was used to validate the numerical model for hydrodynamics and transport. Due to the physics based nature of the AdH numerical model, the validated model could be altered to represent the plan conditions (removal of the Mobile Bay Causeway). Comparisons of the base and plan model results indicate the impacts of removing the causeway are not widespread and are primarily limited to Chocolatta Bay and the areas adjacent to the causeway. The model results suggest an increased exchange of water between Chocolatta Bay (north of the causeway) and Mobile Bay for the removed causeway configuration. Chocolatta Bay also experiences an increased inflow from the river systems which result in increased suspended sediment concentrations and sediment deposition.

River training structures are widely used to create and maintain navigable waterways, to restore rivers and channels in a more stable condition, to promote environmental benefits, and to protect people and infrastructure from damages or floods. Few historical datasets on the changes and impacts in secondary waterbodies resulting from notched river training structures are available for the Lower Mississippi River. Access to the notched training structures on the Lower Mississippi River remains difficult and inhibits data collection for monitoring efforts. This increases the need for alternative methods such as numerical models for assessing the performance of the notched training structures. A quasi-three-dimensional Adaptive Hydraulics model was assembled and used to provide a hydraulic assessment of seven notched river training structures in the Lower Mississippi River. The hydraulic assessment of the notches included assessing the impacts to navigation, the long-term trends, and the potential for aquatic wildlife habitat diversity.