Overwash Controls on Barrier Island Morphodynamics during Storms

Overwash, shoreface retreat, and barrier migration are common processes occurring in transgressive barrier island systems, the scale of which is exacerbated by sea level rise, subsidence and the frequency and magnitude of tropical and extratropical storms. Barrier morphology also clearly plays a key role in determining a morphological response to these processes. Using a hydrodynamic and sediment transport model (MIKE21) and selected barrier island and shoreface templates, informed by deltaic and coastal plain systems in the northern Gulf of Mexico, I performed simulations to determine barrier morphology in response to storms. A low dune with a gentle shoreface slope, characteristic of Louisiana deltaic barriers, demonstrates the greatest amount of shoreline erosion, dune overwash and barrier migration in response to a storm. Profile evolutions over time demonstrate the wider dune templates respond mostly via dune aggradation and barrier rollover whereas the narrow or low templates respond via dune overwash and barrier translation. Determining which barrier templates retain the most sediment over time becomes extremely important when planning coastal restoration projects here in Louisiana