Corps begins gradual closing of Bonnet Carré Spillway as flood levels drop

The U.S. Army Corps of Engineers, New Orleans District, announced this morning that it would begin closing bays of the Bonnet Carré Spillway.

With the Mississippi River slowly going down after being above flood stage for more than five months, the Corps will gradually close the spillway starting with 10 of the 168 bays currently open, the USACE said in a statement.

The bays of the Bonnet Carré Spillway. Photo from the USACE.

Today marks the 74the day the structure has been open. It is the first time the spillway has been operated twice in one year and the first time it has been operated in back-to-back years, the Corps says. The amount of water passing through the spillway peaked on May 21 and 22 at 161,000 cubic feet per second. That’s enough water to fill the U.S. Capitol rotunda in about 8 seconds, according to the Associated Press.

The Bonnet Carré Spillway is designed to prevent the City of New Orleans from flooding when the Mississippi River is above flood stage. It diverts water from the river into Lake Pontchartrain and then out into the Gulf of Mexico. The Corps says that because the river has receded below the maximum flow at Red River Landing, the diversion of water into Lake Pontchartrain is no longer needed to safely pass the river flow through the New Orleans area.

The influx of historic amounts of fresh water from the Mississippi River into the Gulf is responsible for a toxic algae bloom that has every Mississippi beach closed to swimming and wading. Experts say it has also killed off a big portion of the Gulf’s seafood industry. Nearly all of Mississippi’s oyster harvest was devastated this year, along with a big chunk of its annual shrimp haul.

Environmentalists hope that the harmful algae will disappear quickly as the saline levels in the Gulf return to normal levels. Lowered salinity has caused unprecedented numbers of dolphin and sea turtle deaths, they say.

The Corps warns that although water levels are receding, allowing the structure’s closure, the Mississippi River in the New Orleans District’s area of responsibility remains elevated. In the interest of public safety, the Corps will continue its flood fight operations, environmental monitoring and all subsurface construction restrictions remain in effect.