USING SEDIMENT CORE ANALYSES TO INFORM RESOURCE MANAGEMENT PLANNING AND RESTORATION OF SWAN COVE POOL, CHINCOTEAGUE NATIONAL WILDLIFE REFUGE (CNWR), ASSATEAGUE ISLAND, VA

Assateague Island (AI), a barrier island along the Delmarva Peninsula, extends 60 km from Ocean City, MD to the Chincoteague Inlet in VA. CNWR has managed the VA portion of the island for >70 years. In the last 8 decades, south AI (SAI) has elongated nearly 6 km at the expense of northern AI. SAI is migrating west at ~8 m/yr in response to erosion, overwash and sea level rise. Dunes do not recover after large overwash events so the AI beach is flattening and widening at ~4m/yr. Located on SAI, Swan Cove Pool (SCP), is an important, managed wetland habitat that prior to the mid-1940s, was tidally-influenced and had a healthy salt marsh. The construction of Beach Road restricted water exchange between the pool and the estuary, leading to reduced tidal range, lowered salinity, more frequent stagnation, and a decline in Spartina marsh health. Hurricane and Nor’easter storm surges overtop the beach ridge between SCP and the Atlantic Ocean and storm outflows breach the ridge to form temporary inlets into the pool.

Here we tie 11 sediment cores from SCP to historical records and aerial photos. Core analyses include LOI, grain size, magnetic susceptibility, sediment composition and texture, and AMS 14C dating (in progress). By investigating recent (<300 yrs) geological history of SCP we can evaluate environmental change in response to barrier island rollover, storm overwash, and refuge management. Four cores from the E edge of SCP record heterogeneous sedimentation along the marsh edge, and indicate that overwash fans are localized. Within the pool, sedimentation is dominated by modern fine-grained, organic muds and sands, underlain by coarser quartz sands and overwash deposits. A core taken from the center of SCP contains a prominent slag deposit within a layer of quartz sand from 80-88cm. The slag may have washed into the pond from a bike path that eroded in the 90s. CNWR is considering management options for restoration of SCP, the salt marsh, and the beach ridge-dune complex. Their goals are to restore tidal flow and re-establish a healthy salt marsh that will be resilient in the face of rising sea levels and increased storm intensity. Our data will inform Refuge management decisions regarding marsh restoration, and ultimately add to the broader understanding of environmental change impacts on this coastal region.