Louisiana spillway is opened to relieve swollen Mississippi River, spare cities from flooding

In a last-ditch move to relieve stress on levees burdened by floodwaters, the Army Corps of Engineers opened a major Mississippi River floodgate Saturday for only the second time in nearly 40 years, funneling water toward farmland and small communities to save New Orleans and Baton Rouge from inundations.

A crane lifted the metal teeth on one of the Morganza Spillway’s 125 gates, and an avalanche of water began rushing through. The water branched out over the grassy flood plain and began rippling southward toward isolated hamlets, fishing and hunting camps, and towns tucked among the bayous.

It was the first time since 1973 that the Corps has resorted to opening the Morganza Spillway, about 40 miles north of the Louisiana capital, Baton Rouge, and 185 miles upstream from New Orleans. The move underscored the potential for catastrophe if the rain-swollen Mississippi had run unfettered through the state’s two largest cities.

Photos: Mississippi River flooding wreaks havoc in the South

“The system is under tremendous pressure, and it’s going to be under tremendous pressure for quite a long time,” said the Corps’ Mississippi division commander, Maj. Gen. Michael Walsh, at a news conference shortly before the gate was lifted. “This system was really designed back in the 1930s to protect lives, and that’s exactly what we’re doing. We’re using every flood control tool we have.”

Walsh and Lt. Col. Ed Fleming, the Corps’ district commander in New Orleans, outlined a mathematical formula to determine how many gates must be opened before the levees downstream are considered safe. On Saturday, the flow through Baton Rouge reached 1.51 million cubic feet per second, prompting the decision to open one gate in order to bring the flow down to 1.5 million cubic feet per second.

The flow is expected to reach 1.626 million cubic feet per second when the Mississippi crests in Louisiana in about a week. Eventually, enough gates will be opened to reduce the flow by 125,000 cubic feet per second, a process that will take several days.

Local officials have been urging residents in the area to leave. Prison inmates filled sandbags, which were stacked around homes and atop levees in communities expected to receive 5 to 25 feet of water in the coming days. Trailers hauling cattle and horses, U-Hauls filled with furniture, and trucks towing mobile homes lined the narrow roads as locals tried to get out of town.

“It’s going to be bad here,” said Ken Wainwright, who helped his nephew pack up the belongings in his house in Butte La Rose, a tiny bayou where the water is expected to rise to 29 feet.

“What gives them the right to flood us? I mean, I understand it, but … there are so many communities and so many farmers and so many businesses,” Cindy Prejent of Gibson said as she placed sandbags around her home.

Tim Matte, mayor of Morgan City, said people in the area — who each year are reminded in writing that they live in a flood plain — understood the spillway had to be opened to prevent devastating levee failures.

“They’ve taken it as much in stride as you can when your home’s being flooded,” said Matte, whose city of about 12,000 has a floodwall higher than the expected water level. But the wall was built after the last major flooding, in 1973, and remains untested. “Obviously there’s a little bit of apprehension about that, but it’s a big wall and it’s built for this purpose,” Matte said.

“None of these decisions we make are easy,” the Corps’ Fleming said. “I don’t take them lightly.” He said local officials had assured him that everyone in affected communities had been evacuated.

The spillway’s opening means that when the Mississippi River crests in New Orleans in about a week, instead of reaching 19.5 feet — six inches below the top of the city’s armored levees — it will rise to just 17 feet.

The spillway opening had been anticipated as heavy rain and melting snowfall raised Mississippi River levels across several states, leading to drastic measures aimed at saving population centers from disaster. They began earlier this month with the blasting of a levee in Missouri to protect Cairo, Ill.

Photos: Mississippi River flooding wreaks havoc in the South

tina.susman@latimes.com