2011 Mississippi River floods and this connection implies persistence of dry conditions for the next 2 to 3 years. During the 2011 floods, concerns were raised that the Mississippi might divert its main channel into the Atchafalaya Basin if the Old River Control Structure, the Morganza Spillway, or nearby levees failed, or into Lake Pontchartrain if the Bonnet Carré Spillway or adjacent levees failed. Jeff Masters of the "Weather Underground" noted that failure of the Old River Control Structure "would be a serious blow to the U.S. economy, and the great Mississippi flood of 2011 will give [this structure] its most severe test ever."
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