4 minute read
Sabine National Wildlife Refuge
Cameron, Louisiana, United States
Constructing a permanent dredged sediment pipeline for marsh creation. Located in the Chenier Plain ecosystem, the Sabine National Wildlife Refuge (NWR) is the largest coastal marsh refuge on the Gulf. However, saltwater intrusion during tropical storms and from the Calcasieu River Ship Channel has converted significant areas within the Sabine NWR from vegetated intermediate marsh into large areas of shallow brackish water. Wind-driven waves further erode the surrounding marshes. Therefore, through the beneficial placement of material from maintenance dredging of the Calcasieu River Ship Channel, the Sabine NWR Marsh Creation Project strategically re-creates brackish marsh habitat in large, open-water areas of the interior marsh to prevent wind-induced saltwater introduction and freshwater loss. In addition, the placement of dredged sediment nourishes adjacent marshes while reducing open-water fetch (the distance a wave can travel) and further erosion. This multiyear, multiphased project is a partnership between the U.S. Army Corps of Engineers (USACE), the Coastal Protection and Restoration Authority of Louisiana, and the U.S. Fish and Wildlife Service through the Coastal Wetlands Planning, Protection, and Restoration Act of 1990 (CWPPRA). The many cycles of the project allowed land to be built quickly, creating critical wetland habitat in degraded areas.
Article cover: Distichlis spicata (L.) Greene (saltgrass) is the dominant plant species in the area providing nesting grounds for birds and protection from natural erosion along open water areas. (Photo by USACE New Orleans District)
Producing Efficiencies
The team determined that a permanent pipeline from the river to the northeastern corner of the reserve would eliminate the costs and impacts associated with installing a temporary pipeline for each dredge cycle, saving approximately $2 million for each. To give estuarine organisms access to the marsh, the team built some small artificial bayous, known as trenasses. They revised this method after subsequent experience showed that driving a track hoe or marsh buggy over the marsh-creation site one year after construction allowed tidal ingress and egress more effectively and economically than constructing the trenasses.
Using Natural Processes
The project reduces the environmental footprint of the Calcasieu River navigation channel by using dredged sediment to re-create marsh instead of placing the material in limited-capacity upland disposal sites. This dredged sediment nourishes adjacent marsh habitat and improves water quality by filtering pollutants and sediment naturally. It also absorbs water during periods of heavy rainfall. The marsh then releases the excess water more slowly into waterways, reducing the magnitude of any flooding. Smooth cordgrass (Spartina alterniflora) at the marsh perimeter naturally encouraged revegetation throughout the interior of the newly created site.
Broadening Benefits
The channel requires dredging every two years, and by piping it to the refuge, this project re-created approximately 453 hectares of marsh over 5 dredging cycles. It will prevent the loss of existing adjacent marshes and help restore the area’s hydrology. This intertidal marsh habitat, located in a designated Internationally Important Bird Area, benefits a number of rare species, species of concern, and threatened and endangered species, such as least bittern (Ixobrychus exilis), Black Rail (Laterallus jamaicensis), king rail (Rallus elegans), Louisiana Eyed Silkmoth (Automeris Louisiana), and saltwater topminnow (Fundulus notti).
Promoting Collaboration
The collaboration between USACE’s navigation program and the CWPPRA’s ecosystem restoration program was highly beneficial. As USACE already funds the dredging of the Calcasieu River, CWPPRA had to fund only the incremental cost of transporting and placing the dredged sediment in the marsh creation site. By working with the Louisiana Department of Natural Resources, the Coastal Protection and Restoration Authority of Louisiana, the U.S. Fish and Wildlife Service, the Environmental Protection Agency, the Department of Agriculture, and the National Oceanic and Atmospheric Administration, the team received support to construct the permanent pipeline to be used for future marsh creation projects.
