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Protecting Shorelines and Habitat on Craney Island

By David O’Brien, Virginia Field Office, Habitat Conservation Division

If you’ve ever built a sand castle, you know that in the end, the ocean wins. Every time.

This story is about protecting a sand castle on a much grander scale – the sediment depository at the U.S. Army Corps of Engineers’ Craney Island Dredge Material Management Area. To keep the navigation channels in our harbors, rivers, and coastal areas deep enough, The Army Corps uses large dredges to remove the build-up of sediment that naturally occurs over time. That material has to go somewhere, so it goes to designated sites, like Craney Island.

Craney Island is a long artificial spit of sand that extends two miles into the Elizabeth River in Portsmouth, Virginia. It’s surrounded on three sides by winds, waves, and current, and has a perimeter that is 35 feet above mean high tide.

Bird's eye view of Craney Island Dredge Material Management Area,  Credit: Google Earth

Two Problems

The first problem is keeping all that dredged material in place. With  waves constantly battering the site, the perimeter had to be continually shored up and protected. The Army Corps of Engineers has placed concrete rubble, stone sills, and other hardened structures to stabilize the shoreline.

The second problem is making sure that protecting the shoreline doesn’t harm or disrupt the existing habitat for the fish and other marine species that live there. That’s where NOAA’s Habitat Conservation Division comes in.

Keeping the Food Web Intact

Nearshore shallow water habitat is surprisingly important—among the most productive ecosystems in the world. When adjacent to structured habitat, they provide fish with shelter, nursery areas, and food. Some fish eat the plants and many small animals that live here. Many species like blue crabs, bluefish, summer flounder, menhaden, herring, shad, spot, croaker, weakfish, red drum, striped bass, and yellow perch rely on these nearshore areas.

Removing these areas can have devastating effects on these fish species, as well as larger fish and marine animal populations that feed on them. This affects the economic chain, too. Without these fish, our recreational and commercial fisheries suffer, as do the many businesses that support them.

Series of stone breakwaters constructed along the western shoreline of Craney Island to protect perimeter berm from erosion. Photo Credit: David L. O’Brien, NOAA

Tombolos

One shoreline protection strategy is to place clean sand between an offshore stone breakwater and the shoreline to create a “tombolo,” a crescent-shaped intertidal area. This increases protection, but often at the loss of the aquatic habitat, since it’s now covered with sand. The  sand can provide bird nesting habitat, however.

We recently worked with the Corps to construct a different type of shoreline stabilization project. Instead of just placing sand in the tombolos, we worked with the Corps to create nearly 12 acres of “living shoreline.” They planted marsh grasses so that the new tombolo has low marsh, high marsh, tidal channels, as well as the sand beach. Both birds and fish will take advantage of the new habitat.

18 Months Later

Today, the stone breakwaters and living shoreline elements are working together to stabilize the shoreline and provide important shallow water habitat. This project is a good illustration of how even large-scale shoreline stabilization projects can provide healthy fish habitats that support healthy fisheries.