page_title: Bonnet Carré Spillway
section_title: Overview
hierarchical_section_title: Bonnet Carré Spillway / Overview
caption_attribution_description: Construction of Bonnet Carré Spillway, Louisiana, 1929. One of the Corps numerous archived photographs that show navigations, flood fighting, and life along the Mississippi River (Courtesy of the U.S. Army Corps of Engineers)
context_page_description: The Bonnet Carré Spillway is a flood control operation in the Lower Mississippi Valley. Located in St. Charles Parish, Louisiana – about 12 miles west of New Orleans – it allows floodwaters from the Mississippi River to flow into Lake Pontchartrain and thence into the Gulf of Mexico. The construction of the spillway was completed in 1931.
context_section_description: The Bonnet Carré Spillway consists of two basic components: a control structure along the east bank of the Mississippi River and a floodway that transfers the diverted flood waters to the lake. The control structure is a mechanically-controlled concrete weir that extends for over a mile and a half parallel to the river. When opened, the control structure allows overflow volume to flow into Lake Pontchartrain.  The lake's opening to the gulf is sufficient to absorb and dissipate any conceivable volume of flood flow. Thus, the flood surcharge portion of the water from the Mississippi is divided between the main river and the diversion channel; with the surcharge bypassing the New Orleans metropolitan area, resulting in the Mississippi being lower (through that area) than it could have been; and reducing the stress on the area's levees that line the river.  Confined by guide levees, the floodway stretches nearly six miles (10 km) to Lake Pontchartrain, with a design capacity of 250,000 cu ft/s (7,100 m³/s).  The spillway is crossed by U.S. 61 and Interstate 10.
  The spillway was built in response to the Great Mississippi Flood of 1927 that inundated much of the Mississippi River basin.   It was first opened during the flood of 1937, and twelve times thereafter through February 2019 to lower river stages at New Orleans.  The most recent opening began February 27, 2019, when river levels were predicted to rise to minor flood stage in New Orleans on March 19, 2019.  The Army Corps of Engineers initially opened 38 of the 350 bays, and increased this number to 206 bays when the flood crest arrived later in March.  The Army Corps of Engineers closed the spillway on April 11, 2019, only to reopen it again on May 10, 2019.  This marks the first time in the spillway's history that it was opened twice in one year.
caption: Construction of Bonnet Carré Spillway, Louisiana, 1929.
exif: {}