Oyster reef breakwaters are a form of natural infrastructure that is gaining popularity in coastal regions, but there is still a shortage of data and literature on what environmental conditions best suit these structures. A team of IRIS researchers from the College of Engineering and the Odum School of Ecology are working to fill this gap.

Because the reefs are a “living” shoreline, this form of infrastructure requires a consistent food supply and adequate water quality to maintain oyster growth rates. Generally, oyster reefs prefer higher flow speeds and should be inundated with seawater at least 50% of the time to thrive. But how do we find where those ideal conditions are? COAST Lab PhD Student Rebecca Stanley, along with University of Georgia professors Matt Bilskie, Brock Woodson and Jeb Byers, used a combination of environmental models to see where oyster reef breakwaters may be most successful. 

“Ensuring the suitability of the environment is crucial when incorporating oyster reefs as a nature-based solution in coastal infrastructure design.” – Becca Stanley

These researchers set out to explore three main questions: How the height of oyster reef respond to their local hydrodynamic conditions, what flow and depth conditions produce the tallest reefs and best oyster survival and what design frameworks can be created for using living shorelines as nature-based infrastructure.

The study modeled the entire span of an area known as the South Atlantic Bight, a coastal region that runs from near West Palm Beach, Florida to just off of Cape Lookout, North Carolina. The area is characterized by incredibly complex shoreline geometry, with dozens of inlets, estuarine rivers, tidal flats and salt marshes. 

“The model that I developed predicts the height of oyster reefs based on the spatially and temporally varying hydrodynamic conditions of the South Atlantic Bight coast,” Stanley said, “and forecasts how these reefs will reduce wave energy.” The result was a map of estimated reef heights across the entire coast of the state of Georgia.

Height of the reefs directly impacts wave energy: Taller reefs are able to break waves more effectively than short reefs, thereby dissipating wave energy before it reaches the shore. To test this conclusion, the group also ran simulated storm scenarios using a suite of synthetic tropical storms developed by the USACE Coastal Hazards System. The reefs at their predicted heights were observed to reduce maximum significant wave heights across all 8 storms tested.

“It’s incredibly rewarding developing a model that can aid infrastructure design that not only will protect our shorelines, but also provide a variety of ecological benefits,” reflected Stanley.

The team was able to use these results to make suggestions about how best to implement oyster reef breakwaters as a nature-based solution.

Check out the full paper here: A model for understanding the effects of flow conditions on oyster reef development and impacts to wave attenuation