Floods in the United States: 2001–present floodgates of the Morganza Spillway were opened, marking the first use of the gates since the 1973 flood. 330 of the Bonnet Carré Spillway's gates were opened to save the levees protecting New Orleans. There was concern that if the Old River Control Structure, the Morganza Spillway, or the Bonnet Carré Spillway failed, the Mississippi River could change its course, flowing either into the Atchafalaya Basin or Lake Pontchartrain. In early September, the remnants of Tropical Storm Lee had stalled due to Hurricane Katia. As a result, the main cyclone stalled over the Midwest, and a cold front associated with
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