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Louisiana Coastal Wetlands Marsh Terracing Project

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Problems: Louisiana has the highest coastal wetlands loss rate of any state in the nation comprising more than 1,500 square miles of marsh over the past seven decades. Coastal marshes have been deteriorating since man-made navigation channels changed the natural water-flow patterns on the landscape, allowing saltwater to intrude into areas of the marsh where vegetation is less tolerant of high salinity. When this happens, the stressed vegetation dies, which creates large areas of shallow open water and broken marsh. These open-water areas are characterized by relatively unproductive turbid water void of any submersed aquatic vegetation. Marshes adjacent to these large open-water areas are currently experiencing severe erosion caused by wind-generated waves. Twenty-five to thirty-five square miles of the coast’s emergent wetlands are being replaced every year by open-water habitats.

Restoration Strategy: Terraces will be constructed in water depths ranging from one to two feet. Each terrace, arranged in an alternating pattern at 30-degree angles (which makes them look like duck wings from the air), will be 1,000 feet long, 40 feet wide at its base and about 10 feet wide at its top. The surface of each terrace will be approximately two feet above water level and will be planted with vegetation to reduce erosion. They will be designed in a “V” shape so that regardless of the wind direction, calm water will exist on the downwind side of the terrace.

Purpose: The project calls for the construction of approximately 27 linear miles of terraces that will have several functions. The resulting calm water will provide conditions suitable for submersed aquatic vegetation production while the actual terrace crown will provide nesting sites for resident wildlife like the American alligator and mottled duck. Submersed aquatic vegetation and seeds of annual marsh plants are the staples provided by healthy Louisiana coastal marshes that have historically sustained millions of ducks through the fall and winter. The reduction in wave energy will result in reduced shoreline erosion surrounding the project areas. To ensure longevity of each terrace, plugs of smooth cordgrass ( Spartina alterniflora ) were planted at the water’s edge. The project will increase the carrying capacity of wintering, migration, and breeding habitat for wetland-dependent migratory birds, improve and increase fisheries habitat, and will contribute directly to the objectives of the Gulf Coast Joint Venture.

Location: Approximately 24 miles southeast of Lake Charles, LA (Cameron Parish)

Acres Impacted: 6,000 acres

Habitat Type: Coastal Marsh
Submerged Aquatic Vegetation

Partners: Ducks Unlimited, Inc
North American Wetlands Conservation Council
Louisiana Department of Wildlife and Fisheries
Louisiana Department of Natural Resources
U.S. Fish and Wildlife Service
USDA Natural Resources Conservation Service
U.S. Geological Survey
Louisiana Department of Agriculture and Forestry
Cameron Parish Police Jury
Miami Corporation
Sweetlake Land and Oil

Timeline: Construction was completed in spring 2003

DU Contact:

Bob Dew

Regional Biologist
646 Cajundome Blvd., Ste. 180
Lafayette, LA 70506
(337) 291-3065
bdew@ducks.org

 

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