Bonnet Carré Spillway flood of 1937, and ten times thereafter through 2016 to lower river stages at New Orleans. The most recent opening began March 8, 2018, when river levels in New Orleans were predicted to approach the flood stage of at the Carrollton Gauge which is located just upriver from Downtown New Orleans. The floodgate inlet is offset into the Mississippi River bank, at a location that had seen natural flooding for at least two centuries. The concrete structure has been designed to reduce settling into the riverbank. The opening and closing of the spillway is done by lifting out up to
Morganza Spillway 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 Governor of Louisiana, Bobby Jindal, had meanwhile sent a letter on May 4, 2011, to Robert Gates, the United States Secretary of Defense, requesting that the National Guard be deployed under Title 32 of the United States Code status to respond to record water levels in Louisiana, where there was "a significant probability that the U.S. Army Corps of Engineers [would]