Atchafalaya Basin

The Atchafalaya Basin forms the western part of the Mississippi Delta. Under the name of the Atchafalaya Swamp is known as the largest swamp in the USA. The Atchafalaya River occupies a special position within the delta plain of the Mississippi, because he date, apart from the main arm, the only tributary to start their own small growing delta.

Geographical features

For the Atchafalaya Basin with the surrounding flat catchment area of the river backwaters, marsh cypress and the march that receives the brackish water, characteristic. It ends in the cordgrass marsh on the coast of the Gulf of Mexico and comprises the Lower Atchafalaya River, Wax Lake Outlet, the Atchafalaya Bay and the Atchafalaya River and the bayous Chene, Boeuf and Black.

The basin, which is always affected by severe flooding is sparsely populated. It is about 32 km wide and 240 km long. With an area of 2,410 km ² it is the largest swamp wilderness in the U.S. and includes nationally significant expanses of deciduous trees on the lower course of the river, as well as swamps, bayous and backwater lakes. The few roads run through dykes. Interstate 10 crosses the basin on the nearly 30 -mile Atchafalaya Swamp Bridge of Maringouin to Henderson. The Atchafalaya National Wildlife Refuge was established in 1984 to protect the plant communities of endangered species and water birds and migratory birds.

Hydrology of the basin

The Atchafalaya Basin extends between the current and a former main branch of the Mississippi, Bayou Teche today. Since around since 1500 directs the Atchafalaya water from the Mississippi to the sea. Since the path through the Atchafalaya to the coast is shorter and more steeply than going through the eastern route, the taking of the main arm, took the water flow into the Atchafalaya steadily since then. This process was reinforced by the removal of driftwood barriers and by dredging in the 19th century. Only with the completion of the Old River Control Structure, a system of dams and weirs, this process is (for now) been stopped. Today must not exceed 30 % of the water of the Mississippi over the Atchafalaya River to flow into the Gulf of Mexico.

The march and the excess river water

As the flood waters are to curb along the Mississippi River, has been a subject of controversy in recent decades. It is now believed that the drains of the river and the decreasing Verschlickungsrate the surrounding salt marshes with the increasing agricultural use of the Bayou Country - area by the growing population related. The U.S. Geological Survey (USGS ) reports that every year lost over 75 km ² land to the sea.

Due to the decrease in Verschlickungsrate and the decreasing water movement, the containment of the backwaters and the construction of locks by the U.S. Army Corps of Engineers was necessary. The construction of a dyke along the Atchafalaya Basin contributed to the separation of the swamp from the river, which made the inclusion of excess water through the adjacent wetlands to a halt. Thus, the oxygen uptake of the river water was reduced, whereby the color of the water changed brown to black.

The littoral salt marshes form a buffer zone that protects the entire coast of Louisiana from the effects of hurricanes in the Gulf of Mexico and scattered the accompanying storm surges. The march created by the recovery with remote silt, which now settles over the sharp edge of the continental shelf in the artificially channelized flow of the Mississippi River. From the 1950s to the 1970s, the oil industry dredged deep channels in the march to move barges as platforms. The sharp edge crumbled further and there arose broad, shallow channels in the salt marshes.