INVESTIGATING ENVIRONMENTAL CHANGES IN SWAN COVE POOL, CHINCOTEAGUE NATIONAL WILDLIFE REFUGE, ASSATEAGUE ISLAND, VA, IN RESPONSE TO BARRIER ISLAND ROLLOVER, OVERWASH, AND REFUGE MANAGEMENT

Chincoteague National Wildlife Refuge (CNWR) has managed habitats on Assateague Island (AI) for 70+ years. This includes Swan’s Cove Pool (SCP), a restricted, tidal wetland located NE of Tom’s Cove. Prior to the mid-1940s, SCP was tidally-influenced, however the construction of Beach Road cut off most of the water exchange between Little Tom’s Cove and the pool, leading to more stagnant, lower salinity conditions, and a loss of Spartina marsh. Pool sedimentation is dominated by quiet suspension-settling processes interrupted by storm overwash and barrier breach events which deliver coarser sands. Hurricanes and Nor’easters frequently breach this thin strip of island. CNWR is in the planning stages of a full restoration of SCP and salt marsh. The major goals are to restore tidal flow to the pool and re-establish a healthy salt marsh that will be resilient in the face of rising sea levels (3 mm/y) and increased storm intensity.

This study focuses on tieing sediment cores from SCP to historical records and aerial photography to inform the restoration planning process. We have extracted 4 vibracores on the eastern edge of SCP. Core analysis includes loss on ignition for organics, grain size, magnetic susceptibility (MS), sediment composition and texture. Core AIVC 11 was extracted from a modern, subaerially-exposed overwash fan, but aerial photographs show the site was submerged as recently as 2013. In the core, thick deposits of sand overlie fine-grained organic sediments. The organic-rich silts record the pool phase and subsequent sands are fining-upward overwash deposits from ~three major events, each recognized by sedimentologic or MS evidence. Analysis of these cores and aerial photos helps quantify sedimentation rates and shoreline position. The eastern shoreline of SCP is migrating westward by overwash at a rate faster than seaside erosion (11.5m/yr vs 7.2m/yr respectively) all at the expense of beach height. This suggests that the barrier between SCP and the ocean is at risk.

By looking at the recent geological history of SCP we can determine the environmental changes that occurred in response to barrier island rollover, storm overwash, and refuge management. It is our hope that these data will inform the SCP restoration efforts and future management decisions.