Corps considers opening Bonnet Carre'

After a sudden increase in the predicted crest of the Mississippi River at New Orleans, the U.S. Army Corps of En-gineers is considering a recommendation to open the Bonnet Carre’ Spillway.

No opening of the Morganza Spillway, which would divert more water from the Mississippi in the Atchafalaya system, is being contemplated for now, said Rene Poche, public information officer for Corps’ New Orleans District.

“However, as we saw [Wednesday], the forecast can change so we will continue to monitor and are prepared to respond if necessary,” Poche said.

On Tuesday, the Mississippi River was predicted to crest at 16.9 feet at the Carrollton gauge in New Orleans. That would mean a flow of less than the 1.25 million cubic feet per second “operational” trigger that would lead to the opening of the Bonnet Carre'.

That spillway sends water out of Lake Pontchartrain toward the Mississippi coast.

But on Wednesday, the predicted crest at the Carrollton gauge was raised to 17.3 feet, which would top the 1.25 million cubic feet per second trigger, Poche said.

“Based on this forecast and projected flow, the New Orleans District is considering the need to recommend operation of the Bonnet Carre’ Spillway to safely pass this high water through the city of New Orleans,” he said.

At 1 p.m. Wednesday, the National Weather Service said the Atchafalaya at Morgan City was at 6.65 feet, above the 6.0-foot stage that causes minor flooding inside the flood walls. The river is expected to reach 7.1 feet Monday, above the 7.0-foot stage that causes moderate flooding.

Lake Palourde was at 4.54 feet at 1 p.m., above the 4.0-foot “action stage” but below the 5.0-foot flood stage.

Opening the Bonnet Carre’ became controversial after the spillway was opened twice in 2019, the first time that had happened since it was built after the flood of 1927.

A coalition of Mississippi officials and environmentalists sued the Corps and the Mississippi River Commission, alleging that those agencies should have consulted with them before opening the spillway, causing flooding in Mississippi and damage to that state’s saltwater fisheries.

The concern in St. Mary has been that the lawsuit might lead to a greater diversion of Mississippi River water into the Atchafalaya system by way of the Morganza Spillway as an alternative to the Bonnet Carre’. That could mean additional flooding here and additional sediment in important commercial waterways