Tidal Circulation Modeling of a Georgia Coastal Sound
Gross, Thomas F.
Werner, Francisco E.
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The circulation of a tidally forced Georgia estuary is modeled to provide precise prediction of surface currents. These predictions are useful to determine contaminant plume spread (oil spill potential), the transport routes of (shrimp and crab) larvae into the sounds, etc. In the past, they have been used to assist Savannah's 1996 Olympic yachting events. Using a comprehensive nonlinear finite element model which includes tidal- and wind forcing and generates the three dimensional structure of the circulation of Wassaw Sound, we demonstrate the special boundary conditions needed to correctly account for drainage from extensive marsh systems, typical of the US South Atlantic Bight. Tidal forcing from outside the sound is used to specify the interior response of tidal creeks and channels. By synthesizing the back water areas of the marsh flats, the volume of the tidal prism can be correctly modeled without the artificial specification of interior tidal heights. Model results can be used to predict Lagrangian (tracer) pathways, and identifying the "hot spot" regions of mixing between the sound and coastal ocean. Tracer pathways also demonstrate the large variability of residence time within the marsh and sounds encountered by different water masses.