Old River Control Structure Structure to prevent the Atchafalaya becoming the main channel of the Mississippi. The project was completed in 1963, and it completely sealed off the Old river. However, a lock, a diversion channel, and flood spillway were installed to allow barges to pass between the Atchafalaya and Mississippi. The U.S. Army Corps of Engineers measured the amount of water flowing through the Mississippi River and compared it to the amount entering the Atchafalaya Basin by monitoring "latitude flow" at the latitude of the Red River Landing, located five miles downstream of Old River. In this case, latitude flow is a combination
Morganza Spillway 2011 event) had been opened by the Corps of Engineers. The Corps estimated the flow rate at . However, on May 25, new estimates from the U.S. Geologic Survey (USGS) described a much higher rate of , resulting in the closure of 3 bays by May 26, and additional closures by May 29, bringing the total to 11 bays with an estimated diversion rate of . The Corps continued to evaluate the flow and close additional bays as appropriate. By June 6, the number of open gates had been reduced to seven, and by June 8, only two gates were