66 D11. Marine/Coastal Science (Posters)

Sunday, 22 March 2020
1:30 PM - 5:30 PM
Grand Ballroom E–G

USING SEDIMENT CORES TO TRACK ENVIRONMENTAL CHANGE IN SWAN COVE POOL, CHINCOTEAGUE NATIONAL WILDLIFE REFUGE, ASSATEAGUE ISLAND, VA, IN RESPONSE TO BARRIER ISLAND ROLLOVER, OVERWASH, AND REFUGE MANAGEMENT

Paper number: 66-3
Program: Technical Sessions
Time: 1:30 PM – 5:30 PM

Authors

Abstract

Assateague Island (AI), a barrier island along the Delmarva Peninsula, extends 60 km from Ocean City, MD to the Chincoteague Inlet in VA. Chincoteague National Wildlife Refuge (CNWR), has managed the VA portion of the island for >70 years. This includes Swan Cove Pool (SCP), an important wetland habitat. Prior to the mid-1940s, SCP 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. 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.

Here we tie 11 sediment cores from SCP to historical records and aerial photography. 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.

In the last 8 decades, south AI has elongated nearly 6 km at the expense of northern AI. AI is migrating westward at ~8 m/yr in response to erosion, overwash and SLR. Dunes do not recover after large overwash events and AI beach is flattening and widening at ~4m/yr as SCP fills in. Four cores from the E edge of SCP record heterogeneous sedimentation along the marsh edge, and indicate 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.

Our data will inform management decisions regarding marsh restoration, and ultimately add to the broader understanding of environmental change impacts on this coastal region.

Geological Society of America Abstracts with Programs. Vol. 52, No. 2

doi: 10.1130/abs/2020SE-344431

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