Castles are the Marine Corps Air Station’s latest defense tactic. It’s not what you think

Embattled by threatening sea level rise and erosion, nature-based protections for areas near the Marine Corps Air Station Beaufort are forming as part of a $6.8 million push to protect South Carolina’s coast.

The armor comes in the form of interlocking concrete squares with open tops and bottoms that, when puzzled and stacked atop one another, create lines parallel to the shore that become living shoreline reefs. They’re called oyster-castle living shorelines.

The environmentally conscious cobbled reef is what the Department of Defense, The Nature Conservancy and the National Oceanic and Atmospheric Administration say will protect parts of the air base that are already experiencing rapid erosion and flooding issues, which are only expected to worsen.

For part of the air base, at Laurel Bay on the Broad River, the planned 2,000-foot oyster-castle living shoreline will be the first line of defense against storm surge, erosion and flooding. Since the spring, volunteers have built about 20% of the structure.

Living shorelines are “a win-win for everybody,” said Gary Herndon, the air station’s natural and cultural resources manager. “For people, the shoreline, and nature in general. It’s better than hardening the shoreline.”

And it’s due time for this type of long-term solution.

Why oyster castles?

Scientists’ flooding and sea level rise predictions paint a grim future for MCAS Beaufort if it doesn’t intervene.

The Union of Concerned Scientists says in a high-scenario, flood-prone areas within the base’s 6,900 acres could experience tidal flooding more than 300 times a year by 2050. In the worst-case scenario, a Category 4 hurricane would bring 6 feet of sea level rise and maybe double the area exposed to flood depths of 20 feet or more by 2100, the nonprofit organization reported.

Herndon previously told The Island Packet and Beaufort Gazette that being responsible stewards of the land meant addressing current erosion and future projections by working with Mother Nature.

When Herndon and Joy Brown, then-resilient communities program director for The Nature Conservancy, connected in 2022, Brown was working to nab a NOAA grant for living shorelines. Herndon said he knew just the place for it.

Along the Broad River at Laurel Bay, erosion had exposed tree roots, causing the trunks to topple over and die. The particular stretch is near the military housing units. If no action were taken, erosion would eat away at the shoreline and eventually affect properties and community spaces behind it over time, said Nicole Pehl, the Conservancy’s marine conservation coordinator.

In July 2023, NOAA awarded the Conservancy $6.8 million for South Carolina coastal resilience and habitat restoration projects, and a chunk of the funding was funneled into the oyster-castle living shoreline at MCAS Beaufort. The other money is intended to help low-income landowners implement living shorelines on their South Carolina properties.

Nearly a year since getting the grant, the Conservancy has spent $168,895 on 20,930 castles, Pehl said. It’s half of what’s needed to complete the project. They initially budgeted $250,695 for the concrete castles, but because of rising shipping costs, the price of the four-walled blocks has increased significantly.

The Conservancy plans to complete the entire 2,000-foot reef despite likely needing to increase its budget to purchase the remaining castles.

The structure is ideal for the stretch’s conditions, with its gently sloping shoreline, firm sediment and higher salinity, Pehl said. Oyster castles are an environmentally conscious and largely advantageous solution as compared to contentious erosion control structures like sea walls.

When the sandy gray oyster castles are deployed along shorelines, oyster larvae attach to them and grow all while helping reduce wave energy and erosion along the shoreline. Building and placing living shorelines keep the water clean, build up salt marshes, promote vegetation growth, create wildlife habitats and support important local resources, such as the commercial fishing industry.

“We’ve had a lot of success with them in the past,” Pehl said. “They’re good for a variety of energy levels, and there’s a big amount of energy out there, so they shouldn’t move around because they are heavy.”

Two weeks after laying part of the living shoreline, visible sediment had already piled up behind the structure.

“It’s been cool to be able to see so fast that there’s a difference,” Pehl said.

What’s next?

Projected to complete 1,000 feet of the project in 2024, there’s still about 575 feet of heavy lifting to reach that goal.

On Tuesday, an active duty-only team of 80 people built about 75 feet of project in 2.5 hours, while dodging rising tides. The previous volunteer builds were open to the entire community.

MCAS Beaufort isn’t the only military base embracing natural solutions in low-lying areas and needing a helping hand.

In December 2022, the National Fish and Wildlife Foundation awarded nearly $1.2 million from its National Coastal Resilience Fund to Parris Island Marine Corps Recruit Depot and partner organizations to install more than 4,500 wire oyster reefs to cover nearly two acres in Beaufort. Currently, there are two volunteer opportunities to help build those reefs , on July 18 and Aug. 2.

Once the blistering summer heat dissipates, Herndon said they plan to get volunteers back out to the site, battling the tides to lay more oyster castles.