Woodneck Beach and Little Sippewissett Marsh Sand Budget and Flushing Study

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This project was aimed at understanding the variety of coastal and estuarine processes that govern the behavior of a salt marsh inlet and barrier beach complex in Buzzards Bay, and to offer potential options available to the Town of Falmouth to enhance the natural and recreational resources associated with the salt marsh and barrier beach system. 

The long-term management goals for the Town included sustaining the beach and dune as an attractive public resource, maintaining parking and access to the beach, enhancing the dune system, and optimizing tidal exchange through the inlet to potentially improve wetland water quality. 

Tthorough analyses of historical shoreline change, beach cross-shore profile monitoring, wave modeling, sediment transport modeling, and estuarine hydrodynamics were performed to provide the information necessary to propose a plan for the Town to achieve its management goals. An evaluation of recent geological history of the Woodneck Beach Coastal Complex was developed utilizing standard reference materials (maps, aerial photographs, and regional geologic data), as well as knowledge regarding glacial geology and its role in shaping the Massachusetts Coast. Comparison of a 2007 GPS surveyed shoreline position with historical shorelines developed as part of this project provided needed information for the evaluation of sediment movement in this region.

A quantitative analysis of coastal processes was required to develop a defensible sand budget for the Woodneck Beach system.  The computer wave model SWAN and shoreline mode GENESIS were used in this portion of the study.  Numerical analysis techniques alone cannot provide the needed information for a sand budget that also is dependent upon storm-induced changes (overwash) and seasonal cross-shore changes.  Therefore, an analysis of barrier beach overtopping frequency and seasonal changes to the beach shape also was performed.

The technical approach for evaluating salt marsh hydrodynamics included model development and calibration using a two-dimensional, depth-averaged model, capable of simulating hydrodynamics in complex salt marsh and estuary systems.  Water elevations were recorded continuously at two locations: one within Little Sippewissett Marsh and one in Buzzards Bay.  The tide data were then utilized to drive and calibrate the numerical hydrodynamic model.  In addition, salt marsh bathymetry at critical channel cross-sections was measured to ensure accurate representation of the marsh topography/bathymetry within the model.

The suggested management options included two beach nourishment designs, based on the coastal processes modeling, and also the restoration of tidal exchange with an isolated portion of Little Sippewissett Marsh with the placement of a culvert.  The additional tidal flow to the restored area was also shown to help stabilize the inlet to the whole system.

Buzzards Bay, Massachusetts, Shoreline Change, Numerical Modeling, Sediment Transport, Hydrodynamic model, Wave model