LAKE PROVIDENCE, La. —In an agonizing trade-off, Army engineers said they will open a key spillway along the bulging Mississippi River as early as today and inundate thousands of homes and farms in parts of Louisiana's Cajun country to avert a potentially bigger disaster in Baton Rouge and New Orleans.
About 25,000 people and 11,000 structures could be in harm's way when the gates on the Morganza spillway are unlocked for the first time in 38 years.
"Protecting lives is the No. 1 priority," Army Corps of Engineers Maj. Gen. Michael Walsh said aboard a boat from the river at Vicksburg, Miss., hours before the decision was made to open the spillway.
The opening will release a torrent that could submerge about 3,000 square miles under as much as 25 feet of water in some areas but take the pressure off the downstream levees protecting New Orleans, Baton Rouge and the numerous oil refineries and chemical plants along the lower reaches of the Mississippi.
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Engineers feared that weeks of pressure on the levees could cause them to fail, swamping New Orleans under as much as 20 feet of water in a disaster that would have been much worse than Hurricane Katrina in 2005.
Instead, the water will flow 20 miles south into the Atchafalaya Basin. From there it will roll on to Morgan City, an oil-and-seafood hub and a community of 12,000, and then eventually into the Gulf of Mexico, flooding swamps and croplands.
The corps said it will open the gates when the river's flow rate reaches a certain point, expected Saturday. But some people living in the threatened stretch of countryside — an area known for small farms, fish camps and a drawling French dialect — have already started fleeing for higher ground.
Sheriffs and National Guardsmen will warn people in a door-to-door sweep through the area, Gov. Bobby Jindal said. Shelters are ready to accept up to 4,800 evacuees, the governor said.
"Now's the time to evacuate," Jindal said. "Now's the time for our people to execute their plans. That water's coming."