Atchafalaya River

Atchafalaya River
River
Atchafalaya River delta on the Gulf of Mexico; view upriver to the northwest.
Name origin: Choctaw for "long river"
Country	United States
State	Louisiana
Primary source	Mississippi River
Secondary source	Red River of the South
Source confluence	Old River Control Structure
Mouth	Morgan City, Louisiana

The Atchafalaya River /ətʃæfəˈlaɪ.ə/ is a 137-mile-long (220 km)distributary of the Mississippi River and Red River in south central Louisiana 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 hachcha, "river", and falaya, "long".

The Atchafalaya River is navigable and provides a significant industrial shipping channel for the state of Louisiana, as well as the cultural heart of the Cajun Country. 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 for over 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 and Atchafalaya Swamp located in southern Louisiana near the Gulf of Mexico.

The Atchafalaya became a main distributary of the Mississippi in 1839 to 1849 when locals removed a huge log jam (the Great Raft) that was obstructing the Atchafalaya River.

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 7-mile-long (11 km) canalized Old River (part of the Old River Control Structure). It receives the water of the Red as well as roughly 30% of the water of the lower Mississippi (the other 70% continues in its main channel to the southeast). 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, and in times of extreme flooding the Morganza Spillway further downstream.