Army Corps Closes Bonnet Carre Spillway After 28 Days

May 1, 2020

The Army Corps of Engineers closed the final bays of the Bonnet Carre Spillway on Friday, ending the days-long process of closing the flood control structure.

The spillway was open for a total of 28 days. It was first opened this year on April 3.

The Corps uses the Bonnet Carre as a release valve for the Mississippi River, diverting a portion of the river’s flow into Lake Pontchartrain when flood waters threaten to damage levees in the New Orleans area.

This year marks the fifth time the spillway has been opened in the last five years. Historically, it was only used once every decade or so.

Algal blooms often follow spillway openings. Mississippi River water has high concentrations of nutrients from agricultural fertilizers. Those fertilizers encourage toxic algae to grow in coastal waters, which has already closed beaches in Mississippi this year.

The algal blooms also cause areas of little to no oxygen in the ocean — called dead zones — which can kill sea creatures and reduce the harvest of seafood like shrimp.

Support for the Coastal Desk comes from the Greater New Orleans Foundation and the Walton Family Foundation.