IMPACTS OF FUTURE STORMINESS ALONG THE CASTLE NECK BARRIER AND ADJACENT TIDAL INLET SYSTEMS IN THE MERRIMACK EMBAYMENT, MA

Climate change in New England is expected to cause an increase in storm frequency and magnitude (e.g. tropical and extratropical storms), leading to greater precipitation, and stronger wind and wave energy. Coupled with sea-level rise, these events will have significant effects on erosional and depositional patterns along inlet shorelines. In a barrier island setting, intensified storms will increase longshore transport rates and sediment delivery to tidal inlets, which will affect sand bypassing to downdrift shorelines. Greater precipitation will also increase flow in New England estuaries and discharge more sand at the mouths of major New England rivers.

In light of these future changes, we have analyzed historical shoreline changes along Castle Neck, one of the five barrier islands in the Merrimack Embayment. Likewise, we are documenting channel switching and bar migrations at the updrift Plum Island Sound Inlet. These data allow us to assess the impact of storms on the formation/removal of sand deposits and shoals along the beach and within Plum Island Sound Inlet. During the past 25 years, growth of a large protuberance and sequestration of sand along the mid-Castle Neck shoreline have resulted in a 600 m retreat of the southern spit-end of the barrier. More than a million cubic meters of the sand eroded from the spit washed into Essex Bay causing channel migrations and shoaling and building large sand shoals. At the same time, increased wave energy is impacting valuable shellfish beds and wetlands.

We are using remote sensing, hydrodynamic modeling, and grain size trends, to predict the formation and migration of shoals within Essex Bay. Collectively, these studies are aiding in the prediction of how sand will be exchanged among barrier island – tidal inlet reservoirs during a future period of climate change. Our research will help answer questions concerning barrier island shoreline management, inlet channel dredging programs, and beach nourishment practices.