Jim Bradshaw: Rising water raises scary Basin scenario

The National Weather Service is predicting a rapid rise along the lower Mississippi River in the next two weeks. That’s not the rise that will change forever the face of south Louisiana, but, just coincidentally, LSU hydrologist Yi-Jun Xu, has recently joined a list of folks who warn that a really big flood could send most of the Mississippi into the Atchafalaya Basin, permanently, and with disastrous results.
It’s a process that’s been going on for many, many years. The Atchafalaya began seriously stealing water from the Mississippi in the middle 1800s, when a huge log jam was broken to allow easier travel across the Basin. That made the Atchafalaya navigable by steamboat, but also allowed more water to flow into it from the Mississippi.
The added water began to widen the Atchafalaya and dig it deeper, so that it could take even more water. By the late 1940s, it was drawing off fully one-third of the Mississippi’s water. By the 1950s, it became apparent that the shorter, straighter Atchafalaya would soon capture practically all of the Mississippi’s flow.
It was a natural thing to do. Almost all of south Louisiana has been built by sediment from the Mississippi as it meandered from one place to another over the past several thousand years. Mother Nature had no problem with the idea, but lots of people did.
A change in the Mississippi’s course would drain so much water that ships could no longer get to Baton Rouge and only small ones to New Orleans. Industrial plants dependent on fresh water from the Mississippi would have to move elsewhere. The reduced Mississippi flow would allow a tongue of saltwater to creep up the river from the Gulf, corroding pipes and tainting drinking water.
Man’s solution was to build the Old River Control Structure near Simmesport to maintain the Mississippi at necessary levels and control how much water is allowed into the Atchafalaya. The Army Corps of Engineers thought, briefly, about simply building a dam so that all of its water stayed in the Mississippi, but then decided that wouldn’t work.
The Atchafalaya feeds the swamps and bayous of south Louisiana, and is the source of water for many small towns. That was one consideration. But the main one was that the Mississippi can’t handle all of the water that sometimes pours down it; the 1927 flood proved that. New Orleans was saved then by busting the levee and flooding other places. The Simmesport structure had to be designed to essentially become New Orleans’s safety valve, sending water away from the city in flood times, keeping enough the rest of the year to float its boats and feed its commerce.
The controls have done their job since they were completed in 1963. But there have been scares, big ones. In 1973, for example, when the Mississippi reached an historic flood just downstream from the structure, the water began to cut a path around it and to scour beneath it. Tons of rip-rap were poured into the breaches and the structure held, averting disaster—for the time being. But even though more permanent repairs and substantial improvements have been done, some experts think a change in the Mississippi course is inevitable, that some day the manmade structure will give way to the force of nature.
In 1980, two LSU professors, economist David Johnson and civil engineer Raphael Kazman, were among the first to seriously study what might happen. They described the Old River operation as “the scene of a direct confrontation between the United States Government and the Mississippi River” and predicted the river would eventually win. “The final outcome is simply a matter of time,” they said. (“If the Old River Control Structure Fails? The Physical and Economic Consequences,” Louisiana Water Resources Research Institute Bulletin 12, 1980).
They agreed that a diminished Mississippi would spell big trouble for New Orleans and Baton Rouge — forecasting the closed ports, the salt water tongue, and the other effects that had worried the engineers. But they saw just as much trouble on the Atchafalaya if a wall of water should suddenly breach the control. The rush would flood communities worse than in 1927, wipe out road and railroad bridges, break pipelines that supply energy to the Atlantic Seaboard, shut down electric grids here, and cause all sorts of other havoc.
The potential consequences have only gotten worse since that forecast in 1980, in Professor Xu’s view. Such a shift would leave two million people with water too salty to drink. More than 100 petrochemical plants between Baton Rouge and the Gulf of Mexico would be affected. It would cause huge flooding in the Atchafalaya Basin, “Morgan City will probably be gone, covered with water,” he said.
The Corps of Engineers maintains, as it always has, that all is under control at the Old River Control. But there are many folks who, like Kazman and Johnson, think Mother Nature is just biding her time. As one skeptic put it, “The river has a long memory, and, like man, it longs for freedom.”
A collection of Jim Bradshaw’s columns, 'Cajuns and Other Characters,' is now available from Pelican Publishing. You can contact him at jimbradshaw4321@gmail.com or P.O. Box 1121, Washington LA 70589.