Contribution of longshore sand exchanges to mesoscale barrier-island behavior: Insights from the Virginia Barrier Islands, U.S. East Coast

The development of coastal adaptation pathways along sandy barrier-island coasts requires an understanding multi-decadal barrier morphodynamics in response to forcings such as sea-level rise, sediment fluxes, and storminess. Long- cross-shore sand exchanges among barrier-system compartments (shorefaces, beaches, dunes, tidal inlets, backbarrier lagoons) between adjacent islands can play a fundamental role morphology resilience rise. We explore these dynamics through investigation historical areal changes within the 13 largely undeveloped Virginia Barrier Islands United States Mid-Atlantic Coast. pair subaerial island areas mapped from surveys modern aerial satellite imagery with representative thicknesses determined stratigraphic lidar-derived elevation data estimate volumetric time. Overall, lost ~3.4% (16 × 106 m3) their 1887 C.E. volume 2017 loss three central (Parramore, Hog, Cobb)—historically characterized by rotational behavior—was 43% (79 m3). In particular, Parramore Island continuously decreased over 20th 21st centuries. contrast, growth Assateague northern Wallops (located at northern, updrift end chain) resulted increase ~59 m3. Whereas whole modestly size (and thus volume) directly storm impacts accelerating relative rise since mid-1800s, differential behavior south suggests more regional controls on geomorphic behavior. Specifically, we identify roles antecedent substrate, trapping changing wave-refraction patterns associated Island, inter-island barrier-scale behaviors. These findings help better understand underlying mechanisms behind state islands; which change one influences those located several tens kilometers downdrift. This highlights need consider beach management long reaches, even systems are unaffected development, nourishment, shoreline hardening.