During both moderate and severe floods of the Mississippi , the Bonnet Carré Spillway can also be opened to help protect New Orleans , many parts of which are below sea level . The Bonnet Carré Spillway , built after the Great Mississippi Flood of 1927 , is located well downstream of Morganza , where the Mississippi River approaches Lake Pontchartrain near New Orleans . The Corps uses Bonnet Carré to divert floodwaters into the lake in order to protect the levees near New Orleans
Great Mississippi Flood of 1927
Great Mississippi Flood of 1927
Morganza Spillway