Savannah Harbor Expansion Project—Simulating Future Conditions in the Harbor

Tetra Tech has been supporting the USACE Savannah District and the Georgia Ports Authority since 2004 to simulate the effects of harbor deepening for the Savannah Harbor Expansion Project (SHEP). The importance of the model was to evaluate the effects on resources including water quality (salinity and dissolved oxygen), fisheries, and wetlands. With the complex dynamics and various project elements spread geographically in the harbor, a model was necessary to show a holistic picture. Hydrodynamic and water quality models were developed for baseline, also called without-project conditions (years 1999 and 2014), and with-project conditions (meeting/bend wideners, channel deepening, and mitigation features). Based on the SHEP models, the proposed deepening of Savannah Harbor will increase salinity concentrations in the upper reaches of the Savannah River Estuary, including the Middle, Back, and Little Back Rivers, and decrease dissolved oxygen in the Front River. The models determined the need for mitigation projects to compensate for the impacts of deepening and included the following: (1) flow alteration, (2) dissolved oxygen injection, (3) fish passage, (4) wildlife refuge land expansion, and (5) raw water storage for water supply. For example, the flow alteration is a “re-plumbing” of the river and includes removal of the tide gates and abutments, opening of New Cut, closing of Rifle, Houston, and Drakies Cuts, and a flow diversion at McCoy’s Cut. The presentation will describe how the model was able to simulate a combination of mitigation features and will demonstrate the future conditions in Savannah Harbor after the expansion.