Morganza Spillway to add height to the permanent levee by building a supplemental sandbag levee on top of it. However, additional rainfall raised the flood crest higher than even the supplemental sandbags, sending floodwaters over these levees into of cropland located within the floodway. The 2011 Mississippi River floods began to become serious in April. In response, the Corps first analyzed the flooding, and then opened the spillway in a controlled manner. The Corps studied four flooding scenarios, all of which assumed the Bonnet Carré Spillway would be concurrently operating at full capacity (100%). Following this analysis, which showed that extensive flooding
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