Great South Bay After Sandy: Changes in Circulation and Flushing due to New Inlet
The coastal ocean model FVCOM is applied to quantify the changes in circulation, flushing, and exposure time in Great South Bay, New York, after Superstorm Sandy breached the barrier island in 2012. Since then, the lagoon system is connected to the Atlantic via five instead of four inlets. The model simulations are run on two high-resolution unstructured grids, one for the pre-breach configuration, one including the new inlet, with tidal-only forcing, and summer and winter forcing conditions. Despite its small cross-sectional size, the breach has a relatively large net inflow that leads to a strengthening of the along-bay through-flow in Great South Bay (GSB); the tidally driven volume transport in central GSB quadrupled. The seasonal forcing scenarios show that the southwesterly sea breeze in summer slows down the tidally driven flow, while the forcing conditions in winter are highly variable, and the circulation is dependent on wind direction and offshore sea level. Changes in flushing and exposure time associated with the modified transport patterns are evaluated using a Eulerian passive tracer technique. Results show that the new inlet produced a significant decrease in flushing time (approximately 35% reduction under summer wind conditions and 20% reduction under winter wind conditions). Maps of exposure time reflect the local changes in circulation and flushing.
KeywordsMulti-inlet lagoon Breach Circulation Flushing time FVCOM
The authors wish to acknowledge the support of the New York State Department of Environmental Conservation (AM08782 OGL MOU). The findings and interpretations of the data contained in this paper are the responsibility of Stony Brook University and do not necessarily represent the opinions, interpretations, or policy of the Department. Funding for this effort was also supplied by the U.S. National Park Service (P13AC00681). The model simulations were performed on the Extreme Science and Engineering Discovery Environment (XSEDE) platform, which is supported by National Science Foundation grant number ACI-1548562. We are also very thankful for the advice from Lianyuan Zheng from the University of South Florida on how to implement the model dye module. The bathymetric representation of the breach in the model grid is based on surveys conducted by Roger D. Flood and Charles N. Flagg from Stony Brook University and Lidar data was obtained from USGS. Water quality data was obtained from the Suffolk County Department of Health Services.
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