Science / Medicine : Engineers Confront Nature’s Course On the Mighty Mississippi

As if depressed oil prices, a vanishing coastline and hurricanes aren’t enough for coastal Louisianians to worry about, they have a new potential problem on their hands these days. And if it materializes, it could dwarf the other three in terms of economic impact and human misery.

The fear is that the Mississippi River may abandon its present, meandering course through New Orleans and Baton Rouge and cut a new, shorter path farther west on its 2,300-mile flow from its Minnesota headwaters to journey’s end in the Gulf of Mexico.

Realization that this could happen has grown steadily since the turn of the century. And now, at a cost of nearly $500 million, the U.S. Army Corps of Engineers is gambling that it can prevent it. That is the amount already spent in a bold, innovative engineering scheme to force the river to maintain its present course. Without it, the Mississippi probably would have switched channels before now.

But there are others who insist that, no matter how much money or scientific talent is thrown against the mighty river, Mother Nature eventually will prevail, just as Mark Twain predicted a century ago. And that, almost everybody agrees, could result in disaster.

A river diversion may seem unimportant to some, but to Louisianians, the implications are staggering indeed.

The Mississippi is the freshwater supply for 2 million people in the New Orleans-Baton Rouge corridor. And at Baton Rouge, the river supplies coolant for one of the world’s largest petrochemical complexes, which uses 1,600 gallons of water to refine a single barrel of oil.

In both cities, the Mississippi’s riverbed lies below sea level--meaning they would be left on a slack saltwater estuary if the river turned elsewhere and the salty Gulf of Mexico filled in.

The Mississippi began signaling its intentions of abandoning its present channel past New Orleans and Baton Rouge more than a century ago, following a pattern dating back 9,000 years.

Geologists say the river has re-channeled itself about every 1,000 years, seeking an easier route to the gulf as millions of tons of silt carried downstream plugged up the then-existing river delta.

In 1904, an Army survey officer reported that, left alone, the river would eventually be “captured” by the Atchafalaya River, an important north-south Mississippi distributary that flows 80 miles west of New Orleans.

This warning was verified by Corps of Engineers’ studies in the 1970s and ‘80s. The studies found ominously that more and more of the Mississippi’s volume was flowing each year through an old loop that it had once abandoned, known as Old River, 50 miles northwest of Baton Rouge, and then into the Atchafalaya.

Since the Atchafalaya basin is lower and steeper than that of the lower Mississippi, and its juncture with Old River 150 miles closer to the gulf, it was the logical course for the Mississippi to follow.

Thus was born ORCS--the Old River Control Structure--one of the boldest schemes in the Corps’ history.

ORCS consists of two dam-like structures totaling nearly a mile in length. One part--the Overbank Structure--is used only at flood stage, the other--the Low Sill Control Structure--during normal river flow. Today 86 ORCS gates regulate the flow of the Mississippi into the channel, and eventually into the Atchafalaya. Normally, this is limited to 25% or 30% of the river’s volume.

Together, the Old River structures control the flow of the Mississippi to the Atchafalaya through a new, man-made channel. Old River itself was permanently sealed off with an earthen dam, and a lock was built next to it to facilitate navigation between the Atchafalaya and the Mississippi. The project was dedicated in 1962, at a cost of more than $200 million.

But almost immediately, problems arose. Twice during its early years, ORCS was rammed by runaway river barges.

During a 1973 flood, it was rammed again, this time forcing the Corps to close the ORCS for repairs. That same year, under increasing pressure from the river, a cement wing on the upstream side of ORCS broke off. As a result, the river began scouring dangerous holes underneath. Some wondered if ORCS itself might collapse.

“I don’t frighten easily,” declares engineer Raphael Kazmann who in 1973 was a Louisiana State University professor who later wrote a report critical of the ORCS concept. “But when I walked out on that structure at the height of the flood and felt it tremble, I was terrified.”

ORCS survived, weathering an even worse flood a decade later.

Since then, it has been augmented by a newer, six-gate, $200-million auxiliary structure downstream and the Corps now stations two tugboats nearby to stop runaway barges. Yet the fear that it could eventually fail has lingered.

Engineer Kazmann and a colleague, David B. Johnson, an LSU economist, released a study projecting in grim detail what would happen if ORCS were to fail. Even with the addition of the backup auxiliary structure, they argued, it is not a matter of “if,” but “when.”

Kazmann said recently that he “wouldn’t change a word” of that report, written eight years ago.

“You can’t repeal the law of gravity,” he said, referring to the fact that the Atchafalaya basin is both lower and steeper than the Mississippi’s. “The Mississippi is bound to find a new channel. It may be next year or 50 years from now, but it will happen.”

And if it were to happen during a flood, Johnson has calculated, the economic loss to southern Louisiana alone could run as high as $4 billion.

The Atchafalaya basin towns of Morgan City and Berwick, among others, would be virtually destroyed by flooding, he predicted. Moreover, bridges, railroads, four major highways and gas transmission links that feed a major portion of the Atlantic Seaboard would be disrupted, Johnson said.

“What we have here,” said Kazmann, “is a direct confrontation between the United States government and the Mississippi River. And the river will eventually win.”

But Morgan City Mayor Cedric S. LaFleur dismissed that doomsday scenario. “The river won’t switch channels because we simply won’t let it. Someone has said that the Corps of Engineers could run the Mississippi River through downtown Los Angeles if it had enough money, and I believe it,” he said.

If nothing else, ORCS has bought time while engineers decide once and for all if mortals are capable of holding the great river at bay or, if not, how best to prepare for its re-channeling.

For instance, Joseph D. Martinez, a Baton Rouge consulting geologist, has proposed that the Corps of Engineers cut bypass channels through some of the Mississippi’s loops--called oxbows--between New Orleans and the delta. This tactic, he said, could shorten the river by 82 miles and thus relieve some of the pressure on ORCS, since shortening a river makes it flow faster.

Martinez admitted, however, that the cost would be “enormous,” especially where multibillion-dollar riverfront industries, dependent on fresh water, must be relocated.

Others contend that the river might best be left alone. Charles R. Kolb, a consulting professor at LSU’s Institute for Environmental Studies, argued, as an example, that the cost of thwarting the Mississippi’s diversion is an unaffordable alternative to letting the river do its own thing.

“It may be that Louisiana would be better served,” said Kolb, who formerly was with the Corps of Engineers, “if the river were not shackled with artificial engineering restraints at all.”

That opinion would not sit well with the Corps of Engineers, whose overall Mississippi River engineering--including the building of 1,700 miles of levees, technically the world’s longest single structure--is among the most monumental on Earth.

But it would doubtless please Mark Twain, whose name is synonymous with the Mississippi. “Ten thousand river commissions,” Twain once wrote, “cannot tame that lawless stream . . . cannot bar its path with an obstruction.”