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
2011 Mississippi River floods to open more gates on the spillway, the Corps studied four flooding scenarios, all of which assumed the Bonnet Carré Spillway near New Orleans would be concurrently operating at full capacity (100%). Following this analysis, which showed that extensive flooding was expected in the Atchafalaya Basin regardless of the choice made regarding the Morganza Spillway, the Corps decided to start the 2011 diversion by opening the spillway a bit less than described in scenario 1a (21%, not 25%) The Corps of Engineers subsequently released a map showing the estimated times it would take the flood waters to reach the various