Today, the Mississippi writes a parable about going with the flow. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.
Geologist John McPhee stands on the banks of the Mississippi. He watches a boat leave the river, enter locks, and drop 33 feet into a channel called the Old River. That, of course, is all wrong. This is where the watershed of half our nation reaches the sea. It's a watercourse that can reach flow rates of two million cubic feet per second. The idea that it lies above the surrounding landscape is more than all wrong. It's downright frightening.
Downriver, the Mississippi meanders through Baton Rouge, New Orleans, and all the industry in between. This region has been called America's Ruhr Valley -- it is so rich in industry.
But here the Mississippi has built its own bed too high, and is ready to leave it. That threat has been mounting steadily. By WW-II, a third of the Mississippi was overflowing into the Old River and from there to the Atchafalaya River. The Atchafalaya meanders down through the Cajun parishes of south central Louisiana. It was about to become the outlet of the Mississippi. The Corps of Engineers responded by building dams and locks.
The Mississippi has been jumping about like that for thousands of years. Most of Louisiana is made of sand and silt dumped by the River. The Mississippi was shifting its bed during the Trojan Wars. It was shifting again while the Romans built their aqueducts. The Battle of Hastings occurred during its last major move.
Today, a striking feature of the Louisiana map is a long arm of land reaching from New Orleans to the southeast, far into the Gulf -- the lengthening bed of the Mississippi. That arm of silt was a mere stump in my 1898 Britannica.
Ever since the mid-19th century, we've managed to hold the restless River in that place. At first slaves built levees and embankments. When the work proved too dangerous to risk capital property, the task went to Irish immigrants. All the while, cities grew up along the River. Today, industries that must be served by ocean trade march a third of the way into the state.
We've contained the Mississippi's attempt to move for a while. But move it will -- sooner or later. One big flood and it will break through those fragile barricades to reach the low ground it hungers for. When that happens, two hundred miles of fresh-water ports will be left dry, unless we cut a salt-water trench across Louisiana.
Many observers look on attempts to hold the Mississippi as pure hubris. One says, The three most arrogant human projects imaginable are, in descending order, to steal the sun, to make the rivers run backward, and to contain the Mississippi.
The longer we hold this tiger by the tail, the more committed we are to a task that's more difficult every year. The Mississippi warns us, yet again, that nature's intent is inexorable. Nature will yield to our will -- but only so far, and only for a while.
I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.
McPhee, J., The Control of Nature. New York: Farrar Straus Giroux, 1989, Chapter 1, "Atchafalaya."
On the left, the 1897 Encyclopaedia Britannica map of the Mississippi; on the right, a detail from the 1970 edition. The shape of the delta has changed dramatically and the south-eastern portion is far larger today.