Old River

Old River (HM26SZ)

Location: Lettsworth, LA 70753 Pointe Coupee Parish
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Country: United States of America
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N 31° 0.263', W 91° 40.527'

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Lock and Dam

The upper part of Turnbull's Bend filled in and separated from the Mississippi River, but the lower channel grew. It was named Old River and became the point at which the Red, Old and Atchafalaya Rivers meet.The connection between the Mississippi, Red and Atchafalaya rivers began long ago when the Red started flowing toward a large meander of the Mississippi. This meander (later called Turnbull's Bend) intercepted the Red River, turning it into a tributary. The Atchafalaya River also eventually connected with the meander, becoming a distributary. In the mid-1800s, construction of a cut through the narrow neck of Turnbull's Bend made navigation on the Mississippi more efficient. While the upper channel of Turnbull's Bend gradually silted in and separated from the Mississippi, the lower channel—Old River—became an important connection between the three rivers.

After extensive logjams in the Red and Atchafalaya rivers were removed in the 1840s, the Mississippi started showing signs of switching course by sending increasing amounts of water via Old River to the Atchafalaya, which offered a shorter route to the Gulf of Mexico. In the early 1950s it became clear that, without more human intervention, the Mississippi would eventually change course to the Atchafalaya. To prevent this from happening and address

flooding issues, multiple structures and floodways were built over several decades to create the complex controls that define this area today.

From north to south, the entire Old River Control Complex contains the Sidney A. Murray Jr. Hydroelectric Station (completed in 1990), the Overbank Structure and the Low Sill Structure (completed in 1963), the Auxiliary Control Structure (completed in 1986) and the now closed Lower Old River channel.

The Old River Lock, the southernmost part of the Old River Control Complex, is located 11 miles downstream from the main control structures in a canal near the old channel where the Mississippi and Atchafalaya rivers once connected. It was built in 1963 for navigation purposes and provides stable passage for barges and small vessels, connecting the Mississippi to the Red and Atchafalaya rivers. The lock is 75 feet wide, 1,185 feet long and can handle vessel draft depths of 11 feet. A dam constructed north of the lock across Old River prevents the Mississippi River from changing its course.

The lock at Old River is one of four within the Atchafalaya Basin. The others are at Bayou Sorrel, Bayou Boeuf and Berwick. Combined cargo passing through these four locks was 45 million metric tons per year in 2001.

In addition to flood control, the Old River Control Complex provides fresh water to the Atchafalaya Basin—America's

largest river swamp—helping the extensive plant and animal life there thrive and offering a critical corridor connecting the Tensas and Atchafalaya subpopulations of the Louisiana black bear. But with river water comes sediment washed in from upstream farmland. Sediment deposits and changes in water flow caused by floodway construction have stressed the swamp life, requiring even more human participation to maintain remaining habitats.

Visitors to this area can enjoy more than 2,500 acres of land in the area for public recreation, including boating, fishing, birding and camping.
Visit Atchafalaya.org for more information about this site.
This site's geology/geomorphology: Holocene meander-belt (point bar and overbank) deposits of the Mississippi River
HM NumberHM26SZ
Series This marker is part of the series
Placed ByState of Louisiana and National Park Service
Marker ConditionNo reports yet
Date Added Friday, April 13th, 2018 at 1:01pm PDT -07:00
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Locationbig map
UTM (WGS84 Datum)15R E 626449 N 3430840
Decimal Degrees31.00438333, -91.67545000
Degrees and Decimal MinutesN 31° 0.263', W 91° 40.527'
Degrees, Minutes and Seconds31° 0' 15.78" N, 91° 40' 31.62" W
Driving DirectionsGoogle Maps
Area Code(s)225
Closest Postal AddressAt or near LA-15, Lettsworth LA 70753, US
Alternative Maps Google Maps, MapQuest, Bing Maps, Yahoo Maps, MSR Maps, OpenCycleMap, MyTopo Maps, OpenStreetMap

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