BATON ROUGE - Louisiana Gov. Bobby Jindal is saying federal officials have been given approval to open a Louisiana spillway as early as Saturday to avert a Mississippi River disaster in places like Baton Rouge and New Orleans.
Jindal said Friday that the Army Corps of Engineers had received permission to open the Morganza spillway for the first time in 38 years to relieve pressure on river levees. The corps says it will open the spillway when the river flow reaches a certain point, but an exact timing wasn't known.
The governor 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."
CBS News correspondent Dean Reynolds reports that opening the spillway will ease pressure on levees and, at least theoretically, lower the river a foot or more.
It will also lessen pressure on a critical flood control system just up river. Called the Old River Control System, it's designed to literally hold the Mississippi on course.
While the river's basic path has been unchanged for centuries, it's natural inclination is to flow into the Atchafalaya River basin and roll 65 miles west of New Orleans. The control system allows about 30 percent of the Mississippi into the Atchafalaya, while forcing the rest along its traditional route.
If that structure fails and the entire river changes course -- it could be disastrous. By that measure, saving the cities while flooding farmland was seen as the best choice.
In addition to the 2,500 people located inside the spillway who would be impacted by the Morganza opening, there are an additional 22,500 people and 11,000 structures in the backwater area that would face flooding as well, Jindal has said.
U.S. Sen. David Vitter, R-La., said he also spoke with Walsh. He said the corps plans to initially use about 21 percent of the capacity of the spillway, diverting about 125,000 cubic feet of water per second from the Mississippi.
The corps has said the river's flow is approaching 1.5 million cubic feet per second. The corps has recommended to the Mississippi River Commission, on oversight body, that the spillway be opened at that point.
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 would be at risk of flooding.
Even if engineers didn't open the floodgates, no one seems to doubt that a major flood is bound for Butte LaRose, Krotz Springs, the oil-and-seafood hub of Morgan City and other swampland communities in the Atchafalaya Basin.
Port officials were keeping a close watch on the river, which could be closed to traffic in the Baton Rouge-New Orleans corridor as early as Monday.
If the lower portion of the flooding Mississippi River is closed to ships, the U.S. economy could face a bill running into the hundreds of millions of dollars a day.