About a million people live along that corridor, in addition to the New Orleans residents who endured a flooding nightmare six years ago when levees failed after Hurricane Katrina.
So the corps is confronted with a Devil’s choice: cause a flood that would drown the livelihoods of central Louisiana farmers and fishermen, or let the high river roll and frantically sandbag 200 miles of levees to try to prevent flooding in the state’s two biggest cities.
If the swollen Mississippi is allowed to run full bore through the state, the water would eat away at levees and could overtop sections, drowning some districts of New Orleans under about 25 feet of dirty water — an inundation even greater than the Katrina disaster, according to a worst-case map prepared by Walter Baumy, chief of engineering for the corps’ New Orleans office.
But the corps has an ace up its sleeve. It can throw open a relief valve 35 miles northwest of Baton Rouge, the huge Morganza Spillway.
Designed to siphon a fifth of the Mississippi’s mightiest flow and sluice it west, the spillway has been opened just once in the 57 years since its completion, during the flood of 1973.
If thrown open again, the Mississippi would fall, as would the threat to Baton Rouge and New Orleans.
In exchange, a flood would shoot down the gut of central Louisiana and join the already high Atchafalaya River, which would further swell and flood. For 200 miles, farmers and fishermen would pay a steep price as a torrent greater than Niagara Falls would inundate crops, crawfish hatcheries and, possibly, the small cities of Houma and Morgan City. Sensitive oyster beds in the Gulf of Mexico would be imperiled by the pulse of freshwater.
On Wednesday, Louisiana Gov. Bobby Jindal (R) told residents in the path of the potential spillway flood to prepare for evacuation.
“These are very high stakes,” said Bob Thomas, a professor at Loyola University New Orleans who studies the politics and ecology of the spillway. “The Morganza will cause a lot of damage if it’s open, a major flood. But it’s designed for that.”
The Mississippi has flooded 3 million acres in Arkansas, Tennessee and Mississippi and has forced thousands from their homes. On Wednesday, the river set an all-time record at Natchez, Miss. Heavy snows in the upper Midwest this winter and record rains in April across the Ohio River valley triggered the historic floods.
In Louisiana, the Morganza Spillway decision rests with Corps of Engineers Maj. Gen. Michael J. Walsh, president of the Mississippi River Commission, which oversees the river’s flood-control system.
“The river is dictating what we need to do to protect the largest number of lives,” said Robert Anderson, Walsh’s spokesman.