The Atchafalaya cutoff. This has nothing to do with recent flooding in LA ... afaik. But it does say something about the power of nature vs us.
When the US won independence, the Red River rising in CO and traveling between OK and TX drained into the Mississippi. It doesn't anymore. The Atchafalaya river has captured it.
The Mississippi River deposits millions of tons of sediment each year onto the continental shelf of North America in the Gulf of Mexico. As the writer Mark Twain observed, if this process continued unaltered the delta of the Mississippi would extend like a fishing pole from Louisiana to the Yucatan Peninsula. But instead the delta fans out from the lower end of the Mississippi. This occurs partly because the buildup of sediment encourages multiple channels that distribute the flow. But also every thousand or so years the Mississippi finds a new major channel. There has been tremendous economic development along the present main channel which includes the cities of New Orleans and Baton Rouge as well as industrial plants elsewhere dependent upon the Mississippi for fresh water and deep water transportation. Three million people are depending upon the present channel of the Mississippi River. The problem is that the Mississippi is on the verge of switching to a new channel along what is now the Atchafalaya River. The pronunciation of Atchafalaya is a bit troublesome because it is the French spelling of an Indian word. In French "ch" is pronounced as "sh" is in English. Thus "tch" is used in French to denote the English "ch" sound. Therefore the pronunciation of Atchafalaya is as though it were spelled "achafalaya." The Atchafalaya River has already captured the Red River which flows from the west and used to be a tributary of the Mississipi. Already 30 percent of the flow of the Mississippi goes into a channel called the Old River and thence into the Atchafalaya River. The configuration is roughly in the form of an H in which the the Atchafalaya-Red Rivers form the left leg and the Mississippi the other with the Old River being the cross branch. The Old River Control Project of the Corp of Engineers is working to prevent the capture of 100 percent of the Mississippi by the Atchafalaya. But the Corps of Engineers doesn't want to cut off all flow through the Old River because agricultural and marine development along the Atchafalaya River would be hurt. The Corps is committed to maintaining the 30 percent diversion that now exists. Much of the present problem exists because of the past efforts of the Corps of Engineers. Until the nineteenth century about thirty miles of the channel of the the Atchafalaya was blocked by a prehistoric log jam. The Corps and others cleared away this plug of timber. The Red River was also cleared. The Red River had been a direct tributary of the Mississippi for two millenia, but due to the clearing of the Atchafalaya it was captured by the Atchafalaya in the 1940s. Fred Bayley, the chief engineer of the Lower Mississippi Valley Division of the Corp of Engineers, put this way, "The more water the Atchafalaya takes, the bigger it gets; the bigger it gets, the more water it takes." The Old River was once part of the Mississippi. There a meander of the river where it almost looped back upon itself. The Corps decided to eliminate the meander by cutting a channel through the narrowest part. The Corps-made channel was quickly widened by the Mississippi and the meander virtually dried up. This is why the Old River has that name. The Corps also blocked various distributary channels until now only the Atchafalaya diverts water from the main channel. . sjsu.edu
....... The consequences of the Atchafalaya’s conquest of the Mississippi would include but not be limited to the demise of Baton Rouge and the virtual destruction of New Orleans. With its fresh water gone, its harbor a silt bar, its economy disconnected from inland commerce, New Orleans would turn into New Gomorrah. Moreover, there were so many big industries between the two cities that at night they made the river glow like a worm. As a result of settlement patterns, this reach of the Mississippi had long been known as “the German coast,” and now, with B. F. Goodrich, E. I. du Pont, Union Carbide, Reynolds Metals, Shell, Mobil, Texaco, Exxon, Monsanto, Uniroyal, Georgia-Pacific, Hydrocarbon Industries, Vulcan Materials, Nalco Chemical, Freeport Chemical, Dow Chemical, Allied Chemical, Stauffer Chemical, Hooker Chemicals, Rubicon Chemicals, American Petrofina—with an infrastructural concentration equalled in few other places—it was often called “the American Ruhr.” The industries were there because of the river. They had come for its navigational convenience and its fresh water. They would not, and could not, linger beside a tidal creek. For nature to take its course was simply unthinkable.
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On this day, he said, the water on the Mississippi side was eighteen feet above sea level, while the water on the Atchafalaya side was five feet above sea level.
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In the spring high water of vintage years—1927, 1937, 1973—more than two million cubic feet of water had gone by this place in every second. Sixty-five kilotons per second. By the mouth of the inflow channel leading to the lock were rock jetties, articulated concrete mattress revetments, and other heavy defenses. Rabalais observed that this particular site was no more vulnerable than almost any other point in this reach of river that ran so close to the Atchafalaya plain. There were countless places where a breakout might occur: “It has a tendency to go through just anywheres you can call for.”
Why, then, had the Mississippi not jumped the bank and long since diverted to the Atchafalaya?
“Because they’re watching it close,” said Rabalais. “It’s under close surveillance.”
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The Atchafalaya, after all, was a distributary of the Mississippi—the major one, and, as it happened, the only one worth mentioning that the Corps had not already plugged. In time of thundering flood, the Atchafalaya was used as a safety valve, to relieve a good deal of pressure and help keep New Orleans from ending up in Yucatán. The Atchafalaya was also the source of the water in the swamps and bayous of the Cajun world. It was the water supply of small cities and countless towns. Its upper reaches were surrounded by farms. The Corps was not in a political or moral position to kill the Atchafalaya. It had to feed it water. By the principles of nature, the more the Atchafalaya was given, the more it would want to take, because it was the steeper stream. The more it was given, the deeper it would make its bed. The difference in level between the Atchafalaya and the Mississippi would continue to increase, magnifying the conditions for capture. The Corps would have to deal with that. The Corps would have to build something that could give the Atchafalaya a portion of the Mississippi and at the same time prevent it from taking all.
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In 1950, shortly before the project began, the Atchafalaya was taking thirty per cent of the water that came down from the north to Old River. This water was known as the latitude flow, and it consisted of a little in the Red, a lot in the Mississippi. The United States Congress, in its deliberations, decided that “the distribution of flow and sediment in the Mississippi and Atchafalaya Rivers is now in desirable proportions and should be so maintained.” The Corps was thereby ordered to preserve 1950. In perpetuity, at Old River, thirty per cent of the latitude flow was to pass to the Atchafalaya.
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. In 1980, for example, a study published by the Water Resources Research Institute, at Louisiana State University, described Old River as “the scene of a direct confrontation between the United States Government and the Mississippi River,” and—all constructions of the Corps notwithstanding—awarded the victory to the Mississippi River. “Just when this will occur cannot be predicted,” the report concluded. “It could happen next year, during the next decade, or sometime in the next thirty or forty years. But the final outcome is simply a matter of time and it is only prudent to prepare for it.”The Corps thought differently, saying, “We can’t let that happen. We are charged by Congress not to let that happen.”
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In the mid-sixties, a man alone had come down from Wisconsin in a small double-ended vessel with curling ends and tumblehome—a craft that would not have been unfamiliar to the Algonquians, who named the Mississippi. Dugie called this boat “a pirogue.” Whatever it was, the man had paddled it all the way from Wisconsin, intent on reaching New Orleans When he had nearly conquered the Mississippi, however, he was captured by the Atchafalaya. Old River caught him, pulled him off the Mississippi, and shot him through the structure. “He was in shock, but he lived,” Dugie said. “We put him in the hospital in Natchez.”
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newyorker.com
Sooner or later the course of the Mississippi will change to what it's been trying to be for decades. If Rat is alive when that happens, he'll blame it on Exxon and Chevron. |
