Old River Control Structure of 1973 almost caused the control structure to fail. Integrity of the Old River Control Structure, the nearby Morganza Spillway, and other levees in the area is essential to prevent such a diversion. Jeff Masters of "Weather Underground" noted that failure of that complex "would be a serious blow to the U.S. economy." The present Old River Control Structure was completed in 1964 and expanded in 1990. The first two floodgates are the Low Sill Control Structure, which regulates routine flow in the waterway, and the Overbank Control Structure, in use only when the Mississippi exceeds its banks. A navigation
Mississippi River Basin Model 1937, 1943, 1945 and 1952 were reproduced, as well as hypothetical floods at different periods of the year. Tests on individual problems were conducted until 1971 but high costs and growth of computer modelling meant that the facility was put on standby. The last use was in 1973, when a potentially catastrophic failure arose at the Old River Control Structure. The model was used to show that the untested Morganza Spillway could be opened effectively, without diverting polluted water through New Orleans and Baton Rouge, as well as identifying levees that required topping up. In 1993 the site was taken