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Engineering a better beach day: Study identifies critical elevation threshold for barrier island recovery after storms

Driving through almost any coastal town, you'll notice staples of being at the beach: ice-cream stands, seafood shacks, bridges leading to the shore. But what if they all washed away?

Barrier islands, which cover a majority of the Atlantic and Gulf coasts, protect coastal infrastructure, beach towns, and ecosystems—such as marshes, mangroves and seagrass meadows—from damaging storms and high-energy waves. In a recent study in Communications Earth & Environment, researchers from Texas A&M University led by Dr. Orencio Duran Vinent gained a better understanding of what makes a barrier island a "barrier."

The study, which used data from a representative set of barrier islands in Virginia, focused on the transition of barrier islands from their "high" state, in which the islands are richly vegetated barriers with mature dunes, to their "barren" state, where the islands become dune-less and barren.

When a barrier island is in a high state, the dunes act as natural dikes, protecting coastal communities from the impacts of storms and waves. In addition to protecting coastal communities, a healthy dune system allows a barrier island to protect itself from frequent flooding. Over time, flooding and beach erosion of islands in the high state can cause them to lose their dunes and vegetation, creating a barren state. When dunes are lost, so is the protection of the mainland.

A barrier island's elevation also impacts its resilience over time. When barrier islands exist at a lower elevation, it makes them more susceptible to flooding, even from weaker storms and waves, putting them at increased risk of becoming barren.

The results of the study show that there is a threshold elevation at which any barrier island below the elevation is unlikely to recover following a storm. These frequently flooded, dune-less barren islands are a natural endpoint of a barrier island's evolution. To potentially restore them to their high state, coastal engineers need to intervene.

"Modern coastal engineering aims to use natural dynamics rather than concrete constructions, promoting sustainable approaches that include and protect natural systems," said Vinent, an assistant professor in the Department of Ocean Engineering at Texas A&M University. "The resilience of coastal ecosystems after disturbances, such as storms, is crucial for the success of nature-based solutions in coastal engineering."

As research efforts continue, collaboration between coastal engineers and scientists from multiple disciplines, including biology, ecology and geology, will allow for a better understanding of how engineers can work to prevent the loss of coastal infrastructure and recover barrier islands that fall below the elevation threshold for recovery.

"A deeper understanding of the connection between the natural environment and coastal engineering is essential," said Vinent. "A better understanding of the natural dynamics of barrier islands will allow a more timely and effective intervention from coastal engineers, mitigating the risks to coastal infrastructure."

Continued research efforts and collaboration between engineers and scientists from multiple disciplines could make barren barrier islands return to a state of resilience, creating protection for coastal infrastructure, ecosystems, and those beloved days at the beach.