How to prevent erosion using living shorelines

Living shorelines are an alternative to walls along the coast. Learn how they work.

"Welcome! My name is Rachel, and today we're going to be working on a living shoreline project," says Rachel Bisesi, coastal education coordinator at the NC Coastal Federation. "We've had a few work days here at the Nehring house. They wanted to do something to protect their shore from erosion and they decided to put in a living shoreline instead of a hard structure such as a bulkhead." 

Rachel is speaking to a group of volunteers, who pull on gloves and begin to pass bags of oyster shells down toward the shore in an assembly line.

"Living shorelines are built with either rock, or oyster shells or granite or concrete and they're placed a little bit offshore and then planted landward with salt marsh grasses," says Lexia Weaver, Ph.D., a coastal scientist with the NC Coastal Federation. "And what living shorelines do is they protect shorelines from erosion while at the same time helping to create habitat for oysters, fish and crabs."

"As you can probably see once we start laying down these bags, there's a lot of mud and a lot of places where the grass can't grow because whenever we get hurricanes the waves just wash it out," said Hank Nehring, the property owner.

Building a living shoreline is not what homeowners usually do to protect against erosion. More often than not, homeowners fortify their property with artifical walls. According to research from UNC Chapel Hill, 14 percent of the U.S. shoreline has been hardened by bulkheads and seawalls. That's a problem, because hard walls cause scouring and destroy marsh ecosystems. 

"So the big idea behind living shorelines is an alternative to the simplest engineered solution," said Michael Piehler, Ph.D., associate professor with the UNC Institute of Marine Sciences. "If you put a wall in a coastal system that has waves and currents moving along it, eventually it's going to scour. And walls are also not good transitions to the uplands in terms of the ecosystem. They are an abrupt cut. And so the idea of a living shoreline is using natural components in concert to do what a wall would do. So stabilize the sediments, limit wave energy but at the same time you're building fish habitat and our research has shown your removing nutirents."

Too many nutrients in the water can choke out oxygen and lead to fish kills. Living shorelines act like a sponge for excess nutrients. 

"And when they're built with oyester shells, they also improve water quality," said Weaver. "Because each oyster can filter 50 gallons of water per day."

"Our research on oysters alone has shown that the value of oysters to people, the ecosystem services, about 40 percent of that is their nutrient removal," said Piehler. "So that nutrient removal component is a non-trivial part and it's a big part of how people finance or justify the construction of living shorelines."

According the NC Coastal Federation, living shorelines held up well against Hurricane Florence compared to the area's hardened structures. The Coastal Federation is trying to make living shorelines more mainstream. But in order to do that, Piehler says there still needs to be research on how effective they are.

"We're really fortunate to have in this state a ton of people working on this subject," said Piehler. "We'll have a full suite of data to understand how they work, how well they work and what value you're getting as opposed to their cost."