The Atchafalaya River ( french: La Rivière Atchafalaya, es, Río Atchafalaya) is a distributary of the

Mississippi River The Mississippi River is the second-longest river and chief river of the second-largest drainage system in North America, second only to the Hudson Bay drainage system. From its traditional source of Lake Itasca in northern Minnesota, it fl ...

and Red River in south central

Louisiana Louisiana , group=pronunciation (French: ''La Louisiane'') is a state in the Deep South and South Central regions of the United States. It is the 20th-smallest by area and the 25th most populous of the 50 U.S. states. Louisiana is borde ...

in the United States. It flows south, just west of the Mississippi River, and is the fifth largest river in North America, by discharge. The name ''Atchafalaya'' comes from Choctaw for 'long river', from , 'river', and , 'long'.

Atchafalaya Basin

The Atchafalaya River is navigable and provides a significant industrial shipping channel for the state of Louisiana. It is the cultural heart of the

Cajun Country Acadiana (French and Louisiana French: ''L'Acadiane''), also known as the Cajun Country ( Louisiana French: ''Le Pays Cadjin'', es, País Cajún), is the official name given to the French Louisiana region that has historically contained m ...

. The maintenance of the river as a navigable channel of the Mississippi River has been a significant project of the

U.S. Army Corps of Engineers , colors = , anniversaries = 16 June (Organization Day) , battles = , battles_label = Wars , website = , commander1 = ...

for more than a century. Natural development of the river channel, coupled with channel training and maintenance for flood control and navigation, have combined to isolate the river from the swamp. The river valley forms the

Atchafalaya Basin The Atchafalaya Basin, or Atchafalaya Swamp (; Louisiana French: ''L'Atchafalaya'', ), is the largest wetland and swamp in the United States. Located in south central Louisiana, it is a combination of wetlands and river delta area where the At ...

and Atchafalaya Swamp located in southern Louisiana near the

Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United ...

. The Atchafalaya became a main distributary of the Mississippi in 1839 to 1849 when locals removed a huge

log jam A log jam is a naturally occurring phenomenon characterized by a dense accumulation of tree trunks and pieces of large wood across a vast section of a river, stream, or lake. ("Large wood" is commonly defined as pieces of wood more than in diame ...

(the

Great Raft The Great Raft was a gigantic log jam or series of "rafts" that clogged the Red and Atchafalaya rivers and was unique in North America in terms of its scale. Origin The Great Raft probably began forming in the 12th century. It grew from its u ...

) that was obstructing the Atchafalaya River.

Old River Control Structure

The river is formed near Simmesport at the confluence of the Red River with the Mississippi, where the Mississippi connects to the Red River by the canalized Old River (part of the

Old River Control Structure The Old River Control Structure is a floodgate system in a branch of the Mississippi River in central Louisiana. It regulates the flow of water from the Mississippi into the Atchafalaya River, thereby preventing the Mississippi River from chan ...

). It receives 30% of the combined flow of the Red and Mississippi Rivers. (The remaining 70% continues down the Mississippi River.) The volume the Atchafalaya receives from the Mississippi is controlled by the Old River Control Structure, a system of a low-sill structure, an auxiliary structure, an overbank structure, a navigation lock, and a power plant near Red River Landing, Louisiana. In times of extreme flooding, the

Morganza Spillway The Morganza Spillway or Morganza Control Structure is a flood-control structure in the U.S. state of Louisiana. It is located along the western bank of the Lower Mississippi River at river mile 280, near Morganza in Pointe Coupee Parish. The spi ...

further downstream is also used to regulate volume. In 1942 part of the flow of the Atchafalaya River was diverted through

Wax Lake Wax Lake was a lake in St. Mary Parish, Louisiana that was converted into an outlet channel, the Wax Lake outlet, to divert water from the Atchafalaya River to the Gulf of Mexico. History The history of the Wax Lake Outlet, as well as the 20,000 ...

to the Gulf of Mexico further west. During the

2011 Mississippi River floods Major floods along the Mississippi River in April and May 2011 were among the largest and most damaging recorded along the U.S. waterway in the past century, comparable in extent to the Great Mississippi Flood of 1927 and Great Flood of 1993. ...

, the Old River complex was discharging more than into the Atchafalaya River, and the Morganza Floodway was discharging one-fourth of its capacity. If the Mississippi were allowed to flow freely, the shorter and steeper Atchafalaya would capture the main flow of the Mississippi, permitting the river to bypass its current path through the important ports of Baton Rouge and

New Orleans New Orleans ( , ,New Orleans

. Despite control efforts, some researchers believe the likelihood of this event increases each year due to natural forces inherent to river deltas. Atch Egrets-2-LL

The Atchafalaya River

meander A meander is one of a series of regular sinuous curves in the channel of a river or other watercourse. It is produced as a watercourse erodes the sediments of an outer, concave bank ( cut bank) and deposits sediments on an inner, convex ba ...

s south as a channel of the Mississippi, through extensive levees and floodways, past Morgan City, and empties into the Gulf in

Atchafalaya Bay The Atchafalaya Basin, or Atchafalaya Swamp (; Louisiana French: ''L'Atchafalaya'', ), is the largest wetland and swamp in the United States. Located in south central Louisiana, it is a combination of wetlands and river delta area where the At ...

approximately south of Morgan City. Since the late 20th century, the river has been forming a new delta in the bay, the only place on the Louisiana coastline that is gaining ground rather than eroding.

Atchafalaya National Heritage Area

The river's valley was designated

Atchafalaya National Heritage Area Atchafalaya National Heritage Area is a federally designated National Heritage Area encompassing parts of fourteen parishes along the Atchafalaya River in the U.S. State of Louisiana. The heritage area extends the length of the Atchafalaya Basi ...

in 2006.

References

External links

U.S. Army Corps of EngineersJohn McPhee: The Control of Nature - Atchafalaya (''The New Yorker'')
PDF files of publications about and maps of the geology of the Atchafalya River
Louisiana, Morgan City to Port Allen, Including the Atchafalaya River

Coast and Geodetic Survey The United States Coast and Geodetic Survey (abbreviated USC&GS), known from 1807 to 1836 as the Survey of the Coast and from 1836 until 1878 as the United States Coast Survey, was the first scientific agency of the United States Government. It ...

* {{authority control Distributaries Rivers of Louisiana Drainage basins of the Gulf of Mexico Mississippi River watershed Rivers of Avoyelles Parish, Louisiana Rivers of St. Martin Parish, Louisiana Rivers of St. Landry Parish, Louisiana Rivers of St. Mary Parish, Louisiana Atchafalaya National Heritage Area List of place names of Choctaw origin in the United States

Atchafalaya Basin

Old River Control Structure

Atchafalaya National Heritage Area

See also

References

External links