DU uses several approaches to restore and enhance coastal wetlands along the Gulf Coast. In southwestern Louisiana, DU and its partners directly restore coastal marsh by building earthen terraces in shallow, open-water areas where marsh once existed. Terraces help restore wetland habitat by reducing wind-driven wave action, which causes coastal erosion, and improving water clarity, which fosters growth of a variety of beneficial aquatic plants. DU also helps restore and enhance managed coastal wetlands on both public and private lands along the Gulf Coast. This includes the installation of water-control structures and pumps and the repair and maintenance of levees used to manage water and salinity at optimum levels for waterfowl and other wildlife.
In addition, a grant from The McKnight Foundation has enabled DU to work in cooperation with the Louisiana Governor's Office of Coastal Affairs and other partners to advocate for controlled diversions of the Mississippi River in southeastern Louisiana that can rebuild and maintain coastal marsh. One example is the Davis Pond Diversion Structure, completed by the U.S. Army Corps of Engineers in 2002. Located on the west bank of the Mississippi River 22 miles upstream from New Orleans, the structure is used to divert up to 10,650 cubic feet (or about 80,000 gallons) of sediment-laden river water per second into Barataria Basin. Over a 50-year span, the project is expected to preserve 33,000 acres of marsh and benefit more than 750,000 wetland acres. In total, eight small- to moderate-scale diversions have been completed, and 12 more have been proposed or are in the design phase. Many additional large-scale diversions will be necessary to sustain Louisiana's coastal wetlands in the face of future sea-level rise.
The Atlantic coast ranks second after the Gulf in both abundance and density of coastal wetlands. Of the estimated 2.2 million acres of tidal wetlands along the U.S. Atlantic coast, among the most important for waterfowl are located in Chesapeake and Delaware bays and along the shores of New Jersey and Long Island. Located in the heart of the Atlantic Flyway, these wetland-rich coastal ecosystems support the majority of the continent's wintering black ducks, Atlantic brant, and greater snow geese, as well as continentally significant numbers of mallards, scaup, green-winged teal, and other migratory birds.
The mid-Atlantic coast is also home to millions of people. In this densely populated region, vast areas of coastal wetlands have already been dredged or filled, and many remaining wetlands have been impacted by shoreline development. In addition, widespread wetland drainage and clearing of forests in coastal watersheds have degraded water quality in estuaries, killing beds of eelgrass and other submersed aquatic plants that are vital to waterfowl and fisheries. In the future, rising sea levels could erode barrier islands and beaches and drown coastal marshes, compounding wetland losses in the region. Under some sea-level rise scenarios, Chesapeake Bay could lose over 80 percent of its remaining coastal wetlands.