Morphological response of a sandy barrier island with a buried seawall during Hurricane Sandy

• Buried seawall preserved dune heights along barrier island during a hurricane.
• Bay flooding caused catastrophic erosion on barrier island in absence of seawall.
• Buried seawall prevented severe barrier island overwash and inundation.
• Wave force reduced a maximum factor of 1.7 by buried seawall during a hurricane.
• Seawall prevented an additional 5 m of erosion at dune peak during a hurricane.

Coastal populations continue to increase globally, causing potential damage costs of coastal hazards to rise and community resiliency to become a worldwide priority. Recently, Hurricane Sandy (2012) devastated areas of New York and New Jersey and caused overwash and breaching of several urbanized barrier islands along the U.S. eastern seaboard. This study focuses on the morphological response of Bay Head, NJ, a township on a barrier island fronted with a buried seawall. The hydrodynamics and morphology of Bay Head during Hurricane Sandy are simulated with XBeach, a numerical model designed to study these processes during storm events. From the simulations, the seawall protected Bay Head by effectively dissipating wave energy during the peak of the storm and from rapidly increasing bay water levels that flood the backbarrier region of the island. When the seawall is removed from the simulation, dune heights are lowered, allowing bay side flooding to cause a devastating erosive event that completely destroys the remaining dune system. XBeach indicates severe erosion seaward of oceanfront buildings in the absence of a seawall (vertical erosion under the dune peak about 15 m more than in the presence of the seawall), and wave energy propagates further inland even after the storm has passed. However, with the seawall present, wave attack is reduced on the island by a factor of 1.7 and prevents bay side flooding from causing significant morphological change on the island. Therefore, the seawall increased resiliency of the Bay Head community during and after peak Hurricane Sandy forcing by preserving the dune system.