Melting runoff from mountains of snow combined with rainfall 10 times greater than average spread throughout a 200,000-square-mile area within the Mississippi River’s watershed and produced the Great Flood of 2011, which swelled our nation’s mightiest river to historic levels.
Epic floodwaters required heroic responses to control flows that surpassed even the Great Flood of 1927. The 1927 calamity claimed 500 lives, left 600,000 people homeless, and spread its “chocolate tide” in a swath of destruction 80 miles wide and 1,000 miles long, inundating more than 26,000 square miles (16.6 million acres) of land.
The 2011 epic response required using every flood control resource within the Mississippi River watershed, the third largest in the world, to decrease the height of historic crest levels during the flood’s most dangerous hours.
Reservoirs and lakes along the Ohio, Missouri, and Upper Mississippi rivers were filled to capacity and exceeded many historic levels to help keep the lower river’s crests from overtopping the Mississippi River and Tributaries (MR&T) system’s flood control structures.
“The MR&T is a complex system of waterways, rivers, and lakes that USACE [U.S. Army Corps of Engineers] engineers must consider as a whole,” said Maj. Gen. Michael Walsh, then-commander of the Mississippi Valley Division and president of the Mississippi River Commission (MRC). Still, the reservoirs were not enough to stem the steadily rising river and Walsh faced decisions that no engineer wants to make – the deliberate flooding of inhabited floodways to relieve pressure on flood-protection structures farther downstream.
“Making these kinds of decisions was not easy or hard from an engineering perspective, because smart engineers made these same decisions more than 70 years ago when the system was designed,” Walsh said. “Essentially, the river tells us when it’s time to operate the system as designed. The decision to operate was grave, though, because it would lead to loss of property and livelihood, either in the floodway or in an uncontrolled area that was not designed to flood.”
One of Walsh’s colleagues on the MRC, the Honorable R.D. James from Missouri, was personally affected by the decision to operate the Birds Point-New Madrid Floodway, which is located on the west bank of the Mississippi River in southeast Missouri.
“My family’s land lies within the floodway, and I could not displace from my mind what the decision would mean to my friends and neighbors who live and farm the floodway’s 130,000 acres,” James said. “But when the National Weather Service issued a forecast of 63 feet on the Cairo, Ill., gauge on May 2, I realized that a decision on activation was imminent.
“As I sat with Maj. Gen. Walsh throughout the day, my position as a member of the commission weighed heavily on my soul,” James continued. “I knew the decision points of activation were a part of federal law, and that decision lay with the MRC. I know that Maj.Gen. Walsh withheld his order to activate until the moment there was no choice. When he gave the order, I prayed for the safety of all involved, and for all affected. I applaud his delayed and deliberate approach to giving that order, and support him in doing so.”
During a three-day period, activation of the Birds Point-New Madrid Floodway reduced the forecast crest near Hickman, Ky., by 3.8 feet, and prevented the river from overtopping federal levees protecting cities and towns in Illinois, Kentucky, Missouri, and Tennessee.
As waters from the Upper Mississippi and Ohio rivers gathered below the confluence at Cairo on May 3, the river grew to monstrous proportions with flows of more than 2.3 million cubic feet per second (cfs), equal to 25 times the amount of water flowing over Niagara Falls every instant.
Memphis District employees, having worked around the clock preparing for operation of the Birds Point-New Madrid Floodway, were again fully engaged in their second district-wide flood fight in less than two months. On May 10, the river crested at 47.8 feet in Memphis after setting records at New Madrid and Caruthersville, Mo.
“For the Corps of Engineers, the No. 1 priority is public safety,” said Col. Vernie Reichling, Memphis District commander. “We have 150 people out on the levees, walking them, inspecting them, and assisting communities.”
Along the swollen St. Francis River in Arkansas, a tributary of the Mississippi River, Memphis District operated the Huxtable Pumping Plant (the world’s largest storm water pumping station) continuously for almost three consecutive months, approaching the plant’s previous operational record of 120 days of non-stop pumping.
Between May 3 and May 19, the river inundated 6.8 million acres of farmland in unprotected areas between Cape Girardeau, Mo., and the Head of Passes in Louisiana. About 10,000 people evacuated due to backwater flooding.
Despite giving up some ground to allow the river to flex its power, the flood control system operated as designed and saved another 9.8 million acres, thousands of homes, more than four million people, and billions of dollars in infrastructure from inundation. During this same time, two additional decisions were made to protect the integrity of the MR&T system between Baton Rouge and New Orleans – operation of the Bonnet Carré, La., and the Morganza, La., floodways.
Walsh ordered New Orleans District to open Bonnet Carré on May 9 to keep the volume of river flows passing New Orleans at 1.25 million cfs. The spillway protects the integrity of the levees and floodwalls that protect New Orleans.
A more difficult decision soon followed when Walsh ordered the Moganza Floodway opened on May 14. The operation order called for the structure’s deliberate and slow opening to spread the resulting inundation gradually over a one-week period. Morganza is 310 river miles above New Orleans, and at the height of the flooding, 17 of 125 bays were opened with a discharge of about 114,000 cfs.
The operation of both Morganza and Bonnet Carré floodways lowered the flood crest at New Orleans and Baton Rouge by 2.5 feet, protecting a 200-mile-long corridor of levees and floodwalls. Mississippi Valley Division also made history with the opening of Morganza because it represented the first time that the three floodways have operated simultaneously.
“By operating the MR&T system as designed, including the floodways, the value of this investment to our nation can be counted by what we have not lost – lives, critical infrastructure for the energy industry, and more than $50 billion in damages to homes and businesses,” said Col. Ed Fleming, commander of New Orleans District.
On May 19, the river crested in Vicksburg, Miss., setting a record at 57.1 feet. Fortunately, the river did not overtop the Yazoo backwater levees, sparing some 24,000 acres of rich farmland.
“Although we passed the crest today, I believe we’re only one-third of the way through this flood event,” Col. Jeff Eckstein, Vicksburg District commander, said at that time. “We must continue to remain vigilant and keep a close eye on the system until the danger has passed.”
The division worked closely with the U.S. Coast Guard, which, on several occasions, restricted navigation on the flooded river to ensure the integrity of flood control structures. Experienced towboat pilots described the force of the river’s currents as extremely treacherous. Nevertheless, MR&T channel improvements are a critical part of the flood control system in this historic event. Without river bend cutoffs, dikes, and revetments, the ongoing flood would have overwhelmed levees and floodwalls and the communities they protect.
From Cairo to Baton Rouge, flood-stage records have been broken, but where channel improvements have been made at Memphis, Tenn., and Helena and Arkansas City, Ark., river crests have stayed well below prior record levels. This is despite flows near or above those experienced during the 1927 and 1937 floods.
“The Corps has never claimed to tame the Mississippi River, only manage it within the confines of the MR&T system,” Walsh said. “All the MR&T’s flood control features [floodways/spillways, backwater levees, channel improvements levees/floodwalls, gates, pumps, reservoirs, and relief wells] are working in concert to pass historic flows while accommodating the natural tendencies of the Mississippi.
“The MR&T system is performing as designed, but if this same beast is to be managed in future floods, we must soon begin work to repair, rebuild, and reinvest in the infrastructure that saved so much and so many in 2011,” Walsh concluded.
This article first appeared in the 2011-2012 edition of the U.S. Army Corps of Engineers: Building Strong®, Serving the Nation and the Armed Forces publication.