ASSESSING BARRIER ISLAND CHANGE ON ASSATEAGUE AND WALLOPS ISLANDS (MID-ATLANTIC VIRGINIA, USA) AND MODELING IMPACTS OF SEA LEVEL RISE

Barrier islands (BIs) along the Delmarva are dynamic landforms controlled by sea level change, sediment supply, and coastal processes. They protect economically important estuaries and salt marsh nurseries as well as mainland communities from short- and longer-term impacts due to storms and sea level rise (SLR). Within the region these BIs are responding in myriad ways to the effects of global warming. Over the last decade studies have focused on Wallops (WI) and Assateague islands (AI) and BIs further south and document how these BIs are responding to storms and some of the highest rates of SLR in the U.S.. Work has included mapping shoreline change, sediment transport studies, coastal aquifer mapping, and studies of maritime forest soil chemistry and tree health. In addition to these field-based studies, SLOSH and SLAMM models have been built to forecast changes to WI, home of NASA’s Wallops Flight Facility.

Work has revealed historic BI beach retreat rates of 2.9 to 5.5 m/year and are attributed to wash over and longshore transport. Each year the back barrier width decreases and results in a decline of habitat necessary to support valuable fisheries. Shoreline replenishment on both AI and WI has been completed to slow retreat. Yet shoreline change for these and other islands is projected to continue. On AI, plans are being developed to relocate the recreational beach where 1.4 million tourists visit annually to reduce costs and ensure sustainable access to AI National Seashore. Likewise as BIs retreat and geomorphically evolve, aquifers change as fresh water systems respond to salt water intrusion and changes in precipitation. Analysis of maritime forest soils on AI has revealed increases in pH and conductivity, and ultimately a reduction in the acreage of Loblolly Pine (Pinus taeda) forests as dead “ghost forests” expand. Impairment of tree health is exacerbated by Southern Pine Bark Beetle infestations that are changing maritime forest composition, especially on AI. If this pattern continues unabated, the rate of rollover is predicted to increase and this includes the historically stable reaches of BIs. SLR projections show that there may be a tipping point within the next few decades wherein the rate of SLR may outstrip the ability of BIs to keep up and the direct costs to VA’s fisheries/tourism economies will be extreme.