The Nature Conservancy - LMR Atchafalya River

Atchafalya River

The Atchafalaya River is a distributary of the Mississippi and Red rivers; that is, it receives water from the two larger streams rather than emptying into them. From its confluence with the Mississippi, the Atchafalaya runs southward through Louisiana approximately 140 miles to the Gulf of Mexico.

Agricultural and forested lands occupy the northern end of the Atchafalaya’s basin. On the southern end are marshlands and the river’s forming delta at the Gulf. Between those ends lies the largest expanse of swamp wilderness on the North American continent, an area teeming with globally significant diversity of life.

Without the U.S. Army Corps of Engineers’ Old River Control Structure northwest of Baton Rouge, the Mississippi would likely change course and the Atchafalaya would become its main channel. As it is, the Corps, in response to the Great Flood of 1927 on the Mississippi, built a floodway through the heart of the Atchafalaya basin. Enclosed east and west by levees averaging about 15 miles apart, the floodway provides a diversionary route for high Mississippi waters to reach the Gulf, thereby reducing potential flood damages in the downstream urban areas of Baton Rouge and New Orleans.

Within the basin, the Louisiana Department of Wildlife and Fisheries manages as one unit a 43,618-acre tract that includes the U.S. Fish and Wildlife Service’s 15,220-acre Atchafalaya National Wildlife Refuge, the state’s 11,780-acre Sherburne Wildlife Management Area and 16,618 acres owned by the U.S. Army Corps of Engineers.

The Corps has acquired 47,323 acres within the basin and has obtained land preservation and flood passage agreements with owners covering an additional 108,440 acres.

Strategies and Progress

The Conservancy is currently studying ways in which it can contribute to conservation efforts within the Atchafalaya basin and has identified a number of ecological stresses. Forestry practices have altered the basin’s species composition and extent of its woodlands. Alterations to its streams, including levees, have affected natural water flow patterns, allowing some saltwater intrusion and changing some wetlands into dry lands through increased siltation. Development pressures are increasing in the basin south of Interstate 10.

What's to Gain?

The Atchafalaya basin supports more than 200 species of birds, serving as key nesting territory for some and as a critical staging area for migrants crossing the Gulf of Mexico each spring and fall. It is also home to endangered species such as the Louisiana black bear, peregrine falcon and Bachman’s warbler. Economically important harvests of crawfish and fish are produced from the basin, which shelters more than 85 fish species.

Great Rgret, Ardea alba, Atchafalaya National Wildlife Refuge, Louisiana

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The Nature Conservancy and its partners work at sites along the entire length of the Mississippi River, from its headwaters in Minnesota to the Gulf of Mexico.