Federal engineers got the OK to open a massive spillway that would flood hundreds of thousands of acres in Louisiana to try to protect heavily populated Baton Rouge and New Orleans from the bulging Mississippi River.
The Army Corps of Engineers said it will open the Morganza Spillway when the river's flow rate reaches a certain point, expected Saturday.
With that threat looming throughout the day on Friday, some 25,000 people in an area of the Southern United States known for small farms, fish camps, crawfish and a drawling French dialect are hurriedly packing their things and worrying that their homes and way of life might soon be drowned.
Gov. Bobby Jindal said sheriffs and the National Guard will be notifying people vulnerable to flooding from the Morganza in a door-to-door sweep through the area that he says will take anywhere from six hours in some parishes to two days in others.
He said shelters are ready to accept up to 4,800 evacuees if needed.
"Now's the time to evacuate," Jindal said. "Now's the time for our people to execute their plans. That water's coming."
Opening the gates for the first time in 38 years will unleash the Mississippi on a wild ride south to the Gulf of Mexico through the Atchafalaya River and divert floodwater from the river into the basin's swamplands, backwater lakes and bayous. Several thousand homes will be at risk of flooding.
New Orleans Mayor Mitch Landrieu said that the levees around his city could handle the stress of opening the spillway.
"The bottom line is that, as of right now and based on all the information that we have available to us and the information that we believe will be forthcoming ... the situation is that the city of New Orleans is safe," Landrieu said Thursday.
Even if engineers decide not to open the spillway, no one seems to doubt that a major flood is bound for the Louisiana towns of Butte LaRose, Krotz Springs, the oil-and-seafood hub of Morgan City and other swampland communities in the Atchafalaya Basin.
In 1973, the last time the corps opened the Morganza, floodwaters damaged or destroyed many homes and fishing camps in Butte LaRose.
Maxim Doucet was born that year and said his parents stayed put, even when the floodwaters started lapping at the rear of their grocery store. Doucet told The Associated Press that he has no intention of leaving town this time, either.
While most of his neighbors were packing up, Doucet deployed a team of workers and heavy machinery to erect a 6-foot levee around his home on the banks of the Atchafalaya River. A dump truck hauled in roughly 1,000 cubic yards of clay for a bulldozer and front-end loader to fashion a protective ring around the rear of the three-story house.
"I figured I'd give Mother Nature a run for her money," said Doucet, who owns a construction company called Monster Heavy Haulers.
The Morganza and the nearby Old River Control Structure were built in the 1950s to keep the Mississippi on its current course through New Orleans, one of the world's busiest ports. If the river rises much higher at New Orleans, the Coast Guard said Thursday that it would consider restrictions on shipping, including potentially closing the channel to the largest, heaviest ships.
Coast Guard Capt. Ed Stanton said he wants to make sure ships can handle the swollen river.
"My concerns are not only for the height of the river but the velocity of the river," Stanton said.
Farther upstream, the Big Muddy and its tributaries have flooded thousands of acres of the Mississippi Delta. The floodwaters have hit mostly riverfront communities and farmland because most areas are protected by an extensive levee system that stretches from Memphis, Tenn., to Vicksburg, Miss.
But the record high water is putting the levees to the test, and officials are working to prevent a washout of what's known as the backwater levee — not the mainline barrier that runs right along the Mississippi, but the one that protects towns inland from the Yazoo River.
Peter Nimrod, chief engineer for the Mississippi Levee Board, said the backwater levee is designed so that some floodwaters will flow over it and take pressure off the swollen Mississippi. He said the historic flood is likely to "overtop" the levee for about 10 days, but the U.S. Army Corps of Engineers has shored it up with vinyl sheeting in hopes it can withstand the flow.
"But if that overtopping event actually weakens that levee and the levee actually fails, all of a sudden we have thousands of homes underwater, we have towns underwater," Nimrod said, noting that this would be a worst-case scenario — and the difference between about 300,000 acres underwater or 1.2 million acres inundated.
"Rolling Fork, Miss., would be underwater, and everything below that would be underwater. This is a terrible event," he said
Officials in Rolling Fork, best known as the stomping grounds of late blues legend Muddy Waters, were rushing to put out sandbags on the edge of town.
"We're getting ready to have a confrontation with Ol' Man River," Mayor James Denson said.
At a tire store out on Highway 61, Rolling Fork native Joey Walden said the town of 2,800 people is already struggling economically and that a flood could do it in.
"If we get run out of this delta, I don't think I'll come back because there won't be much to come back to. ... There won't be any livelihood here," he told NPR.
In other places, water may drive some families out of their homes, but it's also what will bring them back to repair and rebuild.
In Butte LaRose, five generations of Pamela Guidry's family have called the town home. Her father was a commercial fisherman. Her brothers catch crawfish for money. She worked at a seafood-packing business.
"I didn't want my kids growing up in a city. I wanted them to learn how to live the hard way," she told the AP. "They had to learn how to survive on their own down here. Once you're out of Butte LaRose, you're out in society, out of our own little world."
Guidry said her family weathered the 1973 floods and the great flood of 1927 without any thought of leaving town for good.
"The water receded. They cleaned up. Their lives went on," she said.
NPR's Debbie Elliott in Vicksburg, Miss., and Eileen Fleming of member station WWNO in New Orleans contributed to this story, which contains material from The Associated Press