Only one of the 125, 10-ton steel floodgates on the 4,000-foot long Morganza Spillway in Louisiana was opened Saturday to prevent worse flooding downstream in New Orleans; a cautious first step to give everyone and everything a chance to flee.
"We'll open one bay today. We'll open one or two tomorrow and then we'll open gates based upon the river conditions as they exist," said Col. Ed Fleming, New Orleans district commander of the Army Corps of Engineers.
As the gate was raised, the river poured out like a waterfall, at times spraying 6 feet into the air. Fish jumped or were hurled through the white froth and within 30 minutes, 100 acres of what was dry land was under about a foot of water.
CBS News correspondent Dean Reynolds reports that the Mississippi is cresting now near Helena, Arkansas, over 250 miles north of the Morganza Spillway, so officials in Louisiana know they are in for a period of acute anxiety as they try to manipulate the third longest river in the world.
"This is certainly going to be a marathon and not a sprint as we go through this tremendous, huge amount of water as it comes down," said Gen. Michael Walsh with the Army Corps.
The situation is increasingly urgent, as the amount of stress on the entire flood-prevention system rises.
Saturday's spillway maneuver is designed to ease the stress by diverting some of the Mississippi's flow away from the cities with their riverside industries and onto less populated rural areas. The choice of city over country was made last month when the Corps blew up a levee and flooded Missouri farms to save the city of Cairo, Illinois.
In Louisiana now, 3 million acres - 3,000 square miles - will be flooded. It is a tide toward that is supposed to move well west of Baton Rouge and New Orleans.
By Sunday, the Army Corps predicts the water will be about 25 miles south and a foot or more deep. By Monday, it will be 50 miles south. By Tuesday, the inexorable wave should reach Morgan City, a town of 11,000, where flood preparations have been under way all week.
All told, up to 25,000 people in the new flood zone will be affected, including farmer Ted Glaser.
"It's gonna be a hit. We're gonna change some lifestyles," Glaser said.
What's more, this is Cajun country - a unique slice of Americana with a storied culture to go along with its soybeans and cornfields. Much of it is going under for weeks, or even months.
"We're using every flood control tool we have in the system,'' Army Corps of Engineers Maj. Gen. Michael Walsh said Saturday from the dry side of the spillway, before the bay was opened. The podium Walsh was standing at was expected to be under several feet of water Sunday.
The overall spillway operation could last several weeks.
The Morganza Spillway is part of a system of locks and levees built following the great flood of 1927 that killed hundreds. When it opened, it was the first time three flood-control systems have been unlocked at the same time along the Mississippi River.
By opening the floodgates on this spillway, the hope is to lessen pressure on the floodwalls down to the Gulf of Mexico and prevent a catastrophe. Officials say the move will ease pressure on levees protecting New Orleans, Baton Rouge, and oil refineries and chemical plants downstream.
They haven't opened the spillway at Morganza, La., since 1973, but with the river still rising, they have to do it again.
"Protecting lives is the No. 1 priority," Army Corps of Engineers Maj. Gen. Michael Walsh said at a news conference aboard a vessel on the river at Vicksburg before the spillway was opened.
Portable dams are also being placed on top of the levees in Baton Rouge, said Reynolds.
It is hoped that maneuvering the spillway will keep the river navigable; the last thing anyone wants is to close the river to barge traffic.
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.
The Corps employed a similar cities-first strategy earlier this month when it blew up the levee near Cairo, Illinois, inundating an estimated 200 square miles of farmland and damaging or destroying about 100 homes, with damage that will probably exceed $100 million.
This intentional flood is more controlled, however, and residents are warned by the Corps each year in written letters, reminding them of the possibility of opening the spillway.
The spillway can have a flow rate of 1.5 million cubic feet per second. Just north of the spillway at Red River Landing, the river had reached that flow rate, according to the National Weather Service.
To put things in perspective, corps engineer Jerry Smith crunched some numbers and found that the amount of water flowing past Vicksburg, Mississippi, would fill the Superdome, where the National Football League's New Orleans Saints play, in 50 seconds.
This is the second spillway to be opened in Louisiana. About a week ago, the corps used cranes to remove some of the Bonnet Carre's wooden barriers, sending water into the massive Lake Pontchatrian and eventually the Gulf of Mexico.
That spillway, which the corps built about 30 miles upriver from New Orleans in response to the flood of 1927, was last opened in 2008. May 9 marked the 10th time it has been opened since the structure was completed in 1931. The spillways could be opened for weeks, or perhaps less, if the river flow starts to subside.
In Vicksburg, Miss., Warren County Sheriff Martin Pace said at least five neighborhoods have taken on water.
"We're patrolling subdivisions by boat," Pace said Friday.
U.S. Highway 61, a major north-south route has been cut off by water, affecting thousands of people, Pace said.
Meanwhile, farmers along the lower Mississippi had been expecting a big year with crop prices skyrocketing, but now many are facing ruin, with floodwaters swallowing up corn, cotton, rice and soybean fields.
In far northeastern Louisiana, where Tap Parker and about 50 other farmers filled and stacked massive sandbags along an old levee to no avail. The Mississippi flowed over the top and nearly 19 square miles of soybeans and corn, known in the industry as "green gold," was lost.
"This was supposed to be our good year. We had a chance to really catch up. Now we're scrambling to break even," said Parker, who has been farming since 1985.
More than 1,500 square miles of farmland in Arkansas, which produces about half of the nation's rice, have been swamped over the past few weeks. More than 2,100 square miles could flood in Mississippi.
When the water level goes down -- and that could take many weeks in some places -- farmers can expect to find the soil washed away or their fields covered with sand. Some will probably replant on the soggy soil, but they will be behind their normal growing schedule, which could hurt yields.
Many farmers have crop insurance, but it won't be enough to cover their losses. And it won't even come close to what they could have expected with a bumper crop.
Karsten Simrall, who lives in Redwood, Mississippi, has farmed the low-lying fields for five generations and has been fighting floods for years, but it's never been this bad.
"How the hell do you recoup all these losses?" he said. "You just wait. It's in God's hands."
The river's rise may also force the closing of the river to shipping, from Baton Rouge to the mouth of the Mississippi, as early as next week. That would cause grain barges from the heartland to stack up along with other commodities.
If the portion is closed, the U.S. economy could lose hundreds of millions of dollars a day. In 2008, a 100-mile stretch of the river was closed for six days after a tugboat collided with a tanker, spilling about 500,000 gallons of fuel. The Port of New Orleans estimated the shutdown cost the economy up to $275 million a day.