With Lower Miss On The Rise, Corps To Open Bonnet Carré

The New Orleans Engineer District announced April 2 plans to begin opening the Bonnet Carré Spillway as soon as the following day.

New Orleans District Commander Col. Stephen Murphy recommended the opening to Major Gen. Mark Toy, commanding general of the Corps’ Mississippi Valley Division and president of the Mississippi River Commission, earlier in the day after the National Weather Service raised its forecast for flood levels on the Mississippi River. Toy approved the operation of the spillway.

The Bonnet Carré Spillway, located about 30 miles upriver from New Orleans, is the Corps’ southernmost relief valve for the Mississippi River. The spillway diverts water from the river northward to Lake Pontchartrain. The river water then makes its way toward the Gulf of Mexico via a series of lakes and bays and the Mississippi Sound.

With no action, the National Weather Service forecasts the river will crest at 17.5 feet at the Carrollton Gage in New Orleans. The typical trigger point for operation of the Bonnet Carré Spillway is 17 feet at Carrollton, or 1.25 million cubic feet per second (cfs.).

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“Under these conditions, we now see reaching and exceeding the trigger for operating the Bonnet Carré,” Murphy said in an afternoon press conference April 2.

Murphy later added, “The levees in New Orleans will soon be at the maximum amount they were designed to carry.”

Murphy said he anticipates opening 10 to 20 of the spillway’s 350 bays April 3, with a maximum opening of between 95 and 105 bays. That would amount to a discharge of around 120,000 cfs., he said, though that forecast “doesn’t include future rain, doesn’t include any other weather.”

“Right now we plan on an opening to last four weeks,” he said.

Murphy sought to allay concerns about the opening of the spillway, which will be the fourth such operation in three years. Last year’s high water led to two separate openings and an almost unprecedented discharge of freshwater, which decimated commercial fishing and oyster beds and shuttered beaches across the Gulf Coast due to algae blooms.

“As soon as the structure is no longer needed and it is safe to do so, we will begin closure operations,” he said.

Impacts to navigation were set to begin April 3, with Vessel Traffic Service Lower Mississippi River (VTSLMR) closing the Bonnet Carré Anchorage between Mile 127 and Mile  129. VTSLMR cautioned of possible crosscurrents and eddies due to the diversion through the spillway. The Corps will station a picket boat at the spillway to monitor passing traffic. All recreational areas associated with the spillway are closed.