Record-breaking floods force engineers to blow up Mississippi River levee

On Monday evening, the Army Corps of Engineers will flood farms in southern Missouri to save river towns, after a legal challenge by the Missouri attorney general failed Sunday.

The head of the Mississippi River Commission has given the go-ahead to blow a hole in a 56-mile long levee along the Mississippi River tonight, in an attempt to keep record floodwaters from swamping river towns near the junction of the Mississippi and Ohio Rivers.

The announcement late Monday afternoon caps days of preparation – and legal wrangling – over the move. The breaches, scheduled to be blasted Monday between 9 p.m. and midnight CDT, would mark only the second time in nearly 82 years that the levee, part of the Birds Point-New Madrid floodway, has been activated.

"We have exceeded the record stage already, at Cairo," said Major Gen. Michael Walsh, president of the commission, in a prepared statement announcing the decision. "We are on a course to break records at many points as the crest moves through the system."

"I don't have to like it, but we must use everything we have in our possession ... to prevent a more catastrophic event," he said.

Blowing this section of levee "does not end this historic flood," he said, but engineers say they expect the effort to reduce flood levels by up to four feet at Cairo, Ill., the community in the most immediate danger.

At a briefing over the weekend, Walsh held out the possibility of activating other floodways along the lower Mississippi, if conditions warranted.

The floodway

The Birds Point-New Madrid floodway sits on the west bank of the Mississippi, just below the junction of the Mississippi and Ohio Rivers. It's meant to be a spillway, a broad expanse of former floodplain west of the river. There, floodwaters can spread laterally rather than remaining constricted within the heavily leveed main channel. It allows the river to flood large areas of farmland, reducing water heights upstream and downstream of the floodway.

The floodway is bounded on the east by a levee that hugs the riverbank, and to the west by a 36-mile-long levee. At the upstream end, the levees meet, and then the western levee curves west and south as the Mississippi swings east. At its widest point, the floodway is 11 miles across. Altogether, the floodway covers some 130,000 acres of farmland, all of which will be flooded after the hole is blown near Birds Point.

At the southern (downstream) end, near New Madrid, a gap 1,500 feet wide separates the ends of the two levees, channeling the floodwaters back into the Mississippi's main channel.

Floodway plan: Blow a hole in the levee

The floodway's standard operating plan calls for the Army Corps of Engineers to move barges, laden with explosives, into position along the riverfront levee whenever flooding reaches 59 feet at Cairo. By the time the river reaches 60 feet, the explosives should be set in place. The Mississippi River Commission can give the OK to breach the levee when the river rises to 61 feet at Cairo, with higher levels forecast.

By noon on Monday, the Ohio River at Cairo had reached 61.15 feet. The National Weather Service's Advanced Hydrological Prediction Service estimates the Ohio will crest at slightly more than 63 feet, Wednesday night.

By allowing the water to spread out over the man-made basin, corps officials estimate that they can reduce flood levels at Cairo, Ill., currently the most seriously threatened river town, by up to four feet.

The move also would reduce the height of the flood crest that will continue to work its way south along the Mississippi once it leaves the Ohio.

History of the floodway

The floodway, home to about 300 people (now evacuated), is one of three built after a devastating flood along the lower Mississippi River in 1927.

The corps first used the Birds Point-New Madrid floodway 10 years later, during the Great Flood of 1937, which reached record levels along the Ohio River at Cairo, Ill. Some 3,000 people then lived within the floodway, and had to be evacuated. When the flood stage reached 58 feet at Cairo, the head of the Mississippi River Commission gave the OK to breach the levee.

The effort paid off, reducing the flood stage near Cairo by roughly seven feet. But according to a commission history of the floodway, the 1937 activation also prompted the corps's chief engineer at the time to insist that "no plan is satisfactory which is based on deliberately turning floodwaters upon the home and property of people."

Monday's decision comes after the US Supreme Court denied Missouri's request for an injunction that would have halted efforts to breach the levee. Missouri Attorney General Chris Kostler took his case to the high court over the weekend after a federal district court judge in Cape Girardeau, Mo., refused last Friday to block the preparations of the Army Corps of Engineers.

During that proceeding, the attorneys general for Illinois and Tennessee filed motions in support of the corps's efforts.