Going Green: Sustainable coastal North Carolina tidal marsh still thriving after 16 years
April 25, 2013
In 1996 Wilmington District biologists and engineers, with help from other North Carolina resource agencies, designed and constructed a former dredged material disposal island to offset impacts from construction of the Army Reserve Center in Morehead City, and turned it into a thriving coastal tidal marsh.
Sixteen years later the marsh is a sustainable ecosystem that has exceeded the Corps' goals and expectations. It has weathered numerous tropical storms and hurricanes, and it continues to support a wide variety of flora and fauna. By combining outside-the-box thinking, intuition and scientific studies the site has become a sustainable ecosystem.
"Sometimes it's hard to believe the site is a man-made environment and not a naturally occurring one," said Wilmington District Marine Biologist Chuck Wilson. "Basically we provided the building blocks and then we allowed those natural processes to occur in this site and for the site to mature in a way that Mother Nature intended."
Wilson said there are various attributes scientists look for to determine sustainability. A site needs to be resistant to impacts and stressors such as extreme tides and storms, and it needs to be able to withstand erosion.
"The tide rises and falls twice a day and the site can stand up to that," he said. "But you also want it to be resilient. That means if hit with a hurricane the site can repair itself. In this particular site a hurricane hit right after construction and it overwashed and poured sand into the areas where it had been recently planted with aquatic vegetation. But the site came back. You want the ecosystem to be stable, and it will change over time as new plant species colonize the area and put it on a path for ecological maturity."
Wilson said a good indicator measuring the health of the system is the abundance of colonizing plant species that are still alive after 16 years. He said marsh grasses are seeding and reseeding themselves, and after surveying the marsh-line over the years he's found it has spread down-slope. This indicates the plants are growing and expanding and the ecosystem is still maintaining the basic function for which it was designed.
"We know now that organic material builds up over time and you would not expect to find high organic material in newly constructed marsh," said Wilson. "At this site that organic material began accumulating when plants began to grow and decay much like peat over the seasons."
The area continues to be a living laboratory where scientists like Wilson and those in academia can study its effects. Restoration doesn't happen overnight, and year-to-year analysis shows that once a system gets a good start it can slowly blossom into a thriving ecosystem.
"This is long-term development because marshes will take anywhere from 15 to 30 years to fully develop when they're restored correctly," said Dr. Martin Posey, a University of North Carolina at Wilmington marine biology professor. "If they're not restored correctly then they never really stabilize. We're monitoring this site to see how all the pieces gradually reach the final levels in recent comparison to adjacent areas. The mud flat systems usually equilibrate first, and then your oyster reefs, then marsh edge, and then the final pieces are the upper marshes. We're following that over time for the next decade or two to show how the various pieces begin to develop like a full, stable marsh."
Wilson said building the marsh correctly the first time gave the scientific community confidence to begin constructing other sites along coastal North Carolina. He said the Morehead City site is a good template to observe how science and engineering can recreate a natural, well-functioning ecosystem.
"There are few examples of an ecosystem design that are 16 years old. This is a great place to be able look back and see how these sites develop over time."
The U.S. Army Corps of Engineers strives to protect, sustain, and improve the natural and man-made environment of our nation, and is committed to compliance with applicable environmental and energy statutes, regulations, and Executive Orders. Sustainability is not only part of the Corps' decision processes, but is also part of its culture.