Scientists at the Coastal Studies Institute (CSI), in collaboration with The Nature Conservancy (TNC), are preparing to construct and study a multiple oyster reef breakwater system. This shore protection design is a type of grey-green living shoreline, meaning that non-living, or “grey,” materials are used to encourage the development of a living, or “green,” system. Once installed, the structure will reduce erosion, provide shallow water habitat, and foster establishment of native oyster populations along a high-energy section of estuarine shoreline on Roanoke Island. The study will provide new insight on the viability and effectiveness of oyster sills as a shoreline stabilization method, while serving as an educational tool and future research demonstration site. The project is currently underway and located on a TNC easement on the CSI property in Wanchese, North Carolina. Installation of reef materials is slated for late this Spring and monitoring of the site will be ongoing.
The importance of estuarine erosion control is twofold, as loss of the shorezone threatens both human infrastructure and essential habitat. CSI Coastal Processes Program Head, Dr. Reide Corbett, explains how development in coastal areas alters the natural progression of shoreline change:
“One problem is there just isn’t space for our wetlands to naturally transition up to higher ground along much of our State’s shoreline. When you lose the edge [of the wetland] with no inland area for habitat transition or migration, well, you’re just losing [wetland habitat]. If we want to keep that critical habitat, we have to work out ways to reduce that erosion.”
North Carolina has 12,000 miles of estuarine coast, compared to about 300 miles of beach frontage. While beachfront erosion is a regular fixture in the public consciousness along most coastal communities, Corbett emphasizes the importance of understanding erosion along our estuarine system, too.
“People need to understand how important the estuarine shoreline is and how much we have relative to the beachfront. It is as dynamic as the beach; more importantly, we are losing estuarine shore as quickly as we are on the front side. And, there are better methods out there than just vertical structures along the shoreline to protect it”
Aerial imagery, landscape surveys, and other geospatial records allow scientists to accurately map and analyze local shoreline changes since the 1860’s. The erosion rate along the shores of CSI range from 1-10 feet per year depending on exact location and timescale. By placing a
network of oyster reef breakwaters at approximately 4-ft depth and 130 ft offshore, this project is designed to reduce the wave energy causing that erosion, thus keeping the shoreline and wetland intact for a longer period of time. Additionally, the limestone riprap material of the reef will provide structural habitat for underwater creatures, including oysters, which remove nitrogen and improve water quality. Monitoring of the project will address benthic, ecological, and shoreline changes with a variety of sustained data collection methods.
This project will also play an important role in considering challenges associated with implementing living shorelines as an erosion control method more widely. In addition to variable maintenance and installation costs, a big challenge that Corbett identifies is the cost, duration, and complexity of the permitting process, which varies state-by-state.
“I really see that as a big challenge, and that’s where I think collecting data here, locally, providing that information to our community and the State, and demonstrating that this is a good way to go as far as protecting
and benefiting the ecosystem may lead to a more straight-forward permitting process in the future.”
The breakwater installation along CSI’s campus is a cooperative effort to reduce the rate of shoreline erosion, protect and establish critical habitat, and improve scientific understanding of these types of green-grey systems. Ultimately, CSI sees this project as the first step in creating a test bed for methods of reducing shoreline erosion with various material and designs. The establishment of this research will contribute significantly to public knowledge and the policy-making process surrounding erosion control and shoreline stabilization along our vast estuarine system.