The beginning of the end for the latest Mississippi River flooding has arrived in south Louisiana because water levels will start to slowly fall on Saturday in Baton Rouge, possibly prompting the closure of some bays at Bonnet Carre as early as Monday.
The decision on when to start closing bays at Bonnet Carre depends on the anticipated river flow. The goal is to allow no more than 1.25 million cubic feet of river water per second flowing by New Orleans, said Ricky Boyett, public affairs chief at the U.S. Army Corps of Engineer’s New Orleans district.
On Friday, 210 of the 350 bays on the Bonnet Carre spillway remained open to divert almost 200,000 cubic feet of river water per second to Lake Pontchartrain to keep the Mississippi River below the target level. Boyett said forecasts suggest it could be possible to start closing some of the Bonnet Carre gates on Monday.
“What we don’t want to do is unnecessarily put more water into Lake Pontchartrain than we have to,” Boyett said.
Some gates of Bonnet Carre spillway were opened Jan. 10 to divert some flood waters that came about during heavy rains in December from the Midwest. Normal Mississippi River floods occur in the spring. The Jan. 10 opening was only the second time the Bonnet Carre was needed because of high water in January and only the 11th time it has been operated since it was completed after the historic 1927 flood.
As the water level drops, more bays on the spillway will be closed to keep the flow past New Orleans below the target level but not significantly lower. Given current projections, the entire Bonnet Carre spillway could be closed by Feb. 2, Boyett said.
The gradual closure of gates will likely maintain water levels in New Orleans until the spillway is completely closed.
In Baton Rouge, the crest hit on Monday at 43.3 feet and has hovered around there for the rest of the week. Keeping high water on the levels for a period of time is what the levees were designed for, Boyett said. The gradual decline is preferred because a rapid decline could lead to levee damage or even slides.
“You want to ease the pressure off the levee,” Boyett said.
All forecasts currently point to a nice, gradual fall of water, he said.
The Corps and area levee districts will continue monitoring the river levees daily until the water falls below 15 feet in New Orleans. On Friday afternoon, that level was at 16.5 feet and expected to stay near that level at least until the river falls low enough for the Bonnet Carre to be fully closed.
Corps officials have said they’ve seen fewer problems that need to be addressed along the levee than in the 2011 flood.
When the river level returns to normal, the full picture of what needs to be fixed will be determined in advance of the normal spring snowfall melt that could bring another wave of high water levels to the Mississippi River.
Follow Amy Wold on Twitter, @awold10.