Environmental Review Toolkit
Water, Wetlands, and Wildlife

pic of terrace in salt marsh
Michele Deshotels Planted Terrace. (LaDOTD)
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Planting contractors install smooth cordgrass plugs on the terraces. (Ducks Unlimited)
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Aerial photo of duck-wing terraces. (Greg Linscombe)

Louisiana Department of Transportation and Development

Louisiana's Cameron Creole Watershed - Marsh Terracing Project

It's no wonder a salt marsh terracing project in Cameron Parish, Louisiana, won the 2003 Coastal America Partnership Award. The successful effort to offset transportation impacts by saving an eroding coastal marsh area involved a host of public and private organizations at federal, state, regional, and local levels.

The Louisiana Department of Transportation and Development (LaDOTD) joined forces with the U.S. Fish and Wildlife Service, FHWA, Cameron Parish Police Jury (local government), and Ducks Unlimited to work together on this project. Other partners included the Cameron Parish National Wildlife Refuge (NWR); Gulf Coast Soil and Water Conservation District; Miami Corporation; National Fish & Wildlife Foundation; Shell Oil Company Foundation; North American Land Company; U.S. Army Corps of Engineers; USDA's Natural Resources Conservation Service; USGS's Wetlands Research Center; and Louisiana Departments of Natural Resources, Agriculture and Forestry, and Wildlife and Fisheries.

The partnership grew out of an LaDOTD construction project to improve LA 27, a hurricane evacuation route in the southern part of the state. The improvements called for new paved shoulders which would displace wetlands in existing ditches and need compensatory mitigation. LaDOTD and its partners came up with an innovative mitigation solution which would provide the greatest value for the public's transportation investmen--a solution focused on the marshes of the nearby Cameron Parish NWR. The refuge supports over 45,000 ducks and 10,000 geese during the winter and is home to many other species indigenous to Louisiana.

Unfortunately, the marshes on the refuge were eroding, because high winds and rough waves were allowing salt water to enter lower-salinity areas, killing the vegetation that stabilizes marshes. The remedy? The partnership agreed to create energy-absorbing "plowed" terraces of heavy, dredged clay. The 1,000-foot-long terraces were constructed about 2 feet above the water surface and arranged in an alternating pattern at 30-degree angles. Then smooth cordgrass was planted along the water line. Once established, the plantings quickly filled in the remaining space.

Ducks Unlimited recommended using a 'V'-shape design for the terraces so whatever the wind direction, water would always be calmer on the downwind open-water side of the terraces. From the air, the 'V' terraces look like duck wings.

The accomplishment of the marsh terraces installed on the refuge's East Cove to mitigate the LA 27 wetland impacts was just the beginning. As part of a larger terracing project in Cameron Parish on both publicly and privately owned lands, approximately 28 miles of marsh terracing were constructed, protecting over 3,226 acres of open water and 20 miles of brackish marsh shoreline.

Thanks to the exceptional cooperation among partners, everyone shared in providing either the funds or the expertise. For example, the Cameron Parish Police Jury sponsored the permitting process, enabling the project to be completed faster and Ducks Unlimited supervised the construction work on the terraces.

In October 2002, all but one of the terraces were undamaged by Hurricanes Isidore and Lili. When Hurricane Rita hit Louisiana's southern coast in 2005, causing extensive damage to area marshes, the terraces caught some of the torn marsh.

The pioneering marsh-terracing project does more than promote an emerging technique for restoring and preserving ecosystems. It demonstrates the benefits of mitigating highway impacts with flexible, regional approaches--a model for future cooperative endeavors in Louisiana.

For more information, contact Michele Deshotels at MicheleDeshotels@la.gov

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