HIGH RESOLUTION GIS MAPPING OF SHORELINE CHANGE AT WALLOPS ISLAND, VIRGINIA: A PRELININARY INVESTIGATION OF THE IMPACT OF HURRICANE IRENE

Beaches are highly unstable environments. They are continually altered by wind and waves. Substantial shoreline change is common on seasonal and interannual time scales. Unfortunately, progressive shoreline change has become problematic in vulnerable coastlines. Hurricane Irene demonstrated that coastal management practices need be informed by shoreline change science. This study represents a segment of a broader project initiated in coordination with NASA Wallops Flight Facility and the Chincoteague National Wildlife Refuge to evaluate shoreline change in Wallops Island, Virginia.

Irene occurred August, 25-26, 2011 and resulted in noticeable shoreline change. Although not as large as predicted, this category 1 hurricane still had significant impacts on shorelines along Wallops and Assateague Islands. This study uses GIS to: 1) evaluate longer-term rates of shoreline change at Wallops Island as recorded by aerial photographs over 74 years, and 2) measure more precisely shoreline change attributable to Irene from pre- and post-storm surveys. Our preliminary results show sedimentation patterns on the north end of Wallops have been nonuniform. The far north (aka Cow Gut region) has shown substantial erosion and retrogradation of 10’s of meters with erosion of the beach-dune complex through areas that were previously salt marsh. To the south, the beach area has been prograding oceanward. Sedimentation here is the result of erosion even further south, in the area of launch infrastructure and hard stabilization areas. Based on these assessments, a compartmentalized beach sediment budget is being constructed to evaluate sediment re-distribution patterns through time.