AN ASSESSMENT OF BARRIER ISLAND SHORELINE CHANGE AND GRAIN SIZE VARIATIONS 2011-2022 PRE- AND POST- BEACH NOURISHMENTS: WALLOPS ISLAND, EASTERN SHORE, VIRGINIA

Wallops Island (WI), a barrier island along the coast of Virginia, has experienced century-long shoreline erosion to within meters of NASA’s Wallops Flight Facility (WFF). A localized S-N reversal of longshore transport (LST) and overwash have caused erosion averaging 3.7 m/yr since 1857 on south WI (SWI). Decades of shoreline engineering, dredging, and changes in LST have resulted in seaward progradation of north WI (NWI) by ~1 km since 1930 (~11 m/yr). WI has rotated clockwise at a hinge-point near the N end of a seawall.

Here we present data from a decade of beach morphology and sediment grain size analyses on WI. NASA has performed several major shoreline stabilization projects since 2012 to protect WFF infrastructure. Baseline conditions were established in 2011 in order to track changes in grain size (GS) distribution and shoreline morphology along WI post-nourishment. Beach profiling and sediment sampling (beach face and dune) were conducted monthly (March 2011-Nov. 2012) at 31 sites. We conducted seasonal and post-event sampling from Nov. 2012-Oct. 2022. A major beach nourishment in 2012 created a 6 km long, 70 m wide beach seaward of the seawall. In Oct. 2012, Hurricane Sandy removed ~50% of the new sand. Nourishment reduced the impact of Hurricane Sandy on WI infrastructure and accentuated the rotation of the island as sand moved both N and S of the hinge. A post-Sandy follow-up nourishment occurred in 2014 along eroded sections of SWI. NWI continues to prograde but is stabilizing, while SWI continues to erode. The most recent nourishment of central and SWI was completed Spring 2021 using sediment dredged from the beachface on NWI. Three breakwaters were constructed on central and SWI to retain replenished sand. Our dataset allows us to track placed sand as it redistributes naturally after each stabilization project. Using the USGS Digital Shoreline Analysis System (DSAS), we will calculate shoreline change rates and uncertainties for shorelines between 2012 & 2021. DSAS will also be used to project historic trends into 10- & 20-year future shorelines, predicting future erosion potential. Recent studies put local sea level rise along this shoreline at 3-4 times the global average. Our study highlights the ephemeral nature of beach nourishment and a few of the unintended consequences of this short-term management solution.