After logjams in the Red and Atchafalaya Rivers were removed, the Mississippi threatened to change course by sending increasing amounts of water to the Atchafalaya via Old River. The connection between the Mississippi, Red, and Atchafalaya rivers began when the Red started flowing toward a large meander of the Mississippi later called Turnbull’s Bend, which intercepted the Red River and turned it into a tributary, while the Atchafalaya also eventually connected with the meander and became a distributary. In the mid-1800s, a cut through the narrow neck of Turnbull’s Bend made navigation on the Mississippi more efficient, and as the upper channel 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 were removed in the 1840s, the Mississippi showed signs of switching course by sending more water through Old River to the Atchafalaya, which offered a shorter route to the Gulf of Mexico. By the early 1950s, it had become clear that without further human intervention the Mississippi would eventually change course to the Atchafalaya, leaving the old Mississippi channel a saltwater estuary that would disrupt cities and industries dependent on fresh water and transportation, while the river’s new path would flood the Atchafalaya area and cause further social and economic upheaval. To prevent that course change and address flooding, multiple structures and floodways were built over several decades, including the U.S. Army Corps of Engineers’ Old River Control Complex, which regulates the Atchafalaya so that it takes all of the Red River’s outflow and some of the Mississippi’s, with a 70-30 split in the combined flow of the Red and Mississippi rivers at the latitude of Old River: 70 percent continues down the Mississippi and 30 percent passes down the Atchafalaya. Completed in 1963, the complex included a Low Sill Structure for normal flow and an Overbank Structure for times when the Mississippi exceeded its banks. During the Mississippi River flood of 1973, the Low Sill Structure was nearly destroyed and the Morganza Floodway was operated to relieve pressure. The Auxiliary Structure was completed in 1986 to add emergency capacity during excessive spring floods, and the other elements of the complex are the privately funded Sidney Murray Jr. Hydroelectric Plant at the north end and the Old River Lock and Dam at the south end. By 1990, all five structures were completed and operational. During the peak of the Mississippi River Flood of 2011, when the complex discharged 706,000 cubic feet per second of water, the structure at Morganza was opened for only the second time in history; the floodway system functioned as intended, though the power of nature remained formidable.
