A deluge waiting to happen

Nature will do as nature does, but humans are to blame for the deadly Midwestern floods.

By Katharine Mieszkowski

Read more: Environment, Politics, Science, News, Nature, Katharine Mieszkowski, Environment & Science

Reuters/Frank Polich

Houses sit in floodwater from the Mississippi River in La Grange, Mo., June 18, 2008.

July 3, 2008 | The floodwaters are starting to ebb in the swollen Mississippi, which in the past few weeks has seen its worst flooding in 15 years. Since May, at least 24 people have died from the torrential rains and flooding, more than 38,000 people have evacuated their homes and an estimated 5 million acres of corn and soybean have been waterlogged. But as the great mop-up begins, some scientists contend this is one natural disaster that is by no means just natural: It is the dramatic result of more than 100 years of narrowing and constricting the river.

"There is a widespread pattern of flood levels getting higher and flooding becoming more frequent," says Nicholas Pinter, a geologist at Southern Illinois University Carbondale. Pinter and colleagues charge that structures built by the U.S. Army Corps of Engineers to aid the shipping industry are contributing to the flooding. They're calling for the National Academy of Sciences to have oversight over Army Corps river projects, and for the federal agency to refrain from building structures that exacerbate the floods.

"The Army Corps of Engineers certifies its own projects. It's kind of like children giving themselves their own grades," says Robert Criss, professor of geology at Washington University in St. Louis. "There's a definite conflict of interest there." Pinter was in Washington, D.C., last week lobbying Sen. Dick Durbin of Illinois, among other members of Congress, about how the government's own actions have contributed to the horrific flooding. Criss, Pinter and other geologists are also organizing a conference on the issue for this fall.

Even before the recent deluge, scientists sounded the alarm. Back in March, weeks before the floods occurred, Criss, Pinter and professor Timothy Kusky of St. Louis University sent a letter to the commander for the St. Louis district of the Army Corps of Engineers, critiquing the new structures that the agency puts into the Mississippi and Missouri to make it easier for large barges to navigate the area. "These structures are loaded cannons pointing at St. Louis and East St. Louis, waiting to go off during the next large flood," wrote the scientists.

That warning went unheeded, as did similar warnings after the last great floods in 1993, which caused $20 billion in damages and killed almost 50 people. In fact, way back in 1933, one observer noted "flood magnification" caused by "dikes and revetments used in shaping and controlling the stream for modern barge transportation." In 1975, a milestone paper by the late Charles Belt of St. Louis University found a record flood level in St. Louis in 1973, but not a record flood flow of water. In other words, less water was causing higher water.

"He was complaining that the channel was obviously changed in St. Louis Harbor and elsewhere," says Criss. "It was clearly a reflection of the constriction of the river."

The dramatic reengineering of the Mississippi through levees and other structures has been going on for over 100 years. Way back in 1837 when then-Lt. Robert E. Lee of the Army Corps of Engineers mapped the Mississippi at St. Louis, it was almost 4,000 feet wide. Today it's just 1,500 feet wide at St. Louis. The Missouri river has also been drastically shrunk. "The lower Missouri for hundreds of miles is only half the width that it was historically," explains Criss.

Levees, which are essentially piles of mud, dirt, clay and gravel, permit farming and development on the historical flood plain, yet greatly narrow the river's course. "Where levees are added to the flood plain, they take away the capacity of the flood plain to both store and take away water," says Pinter. Revetments, which line the river banks with boulders and concrete, prevent the river from meandering, which protects valuable land on the flood plain and makes the river straighter for shipping.

Now that the river can't naturally spread out on its flood plain or meander, the extra water under flooding conditions has nowhere to go. "If floodwaters can't spread out as they would in a natural flood plain environment, they can only go up," explains Criss. Other structures placed in the rivers' waters have made the problem worse.

Next page: Building more levees is the wrong way to the future