Tuesday, May 3, 2011

The River's Rising, There's Gonna Be a Flood

And a lotta good people will be buried in the mud.

One topic that I can "geek out" about for a good long while is riparian geography. Seeing that this year's spring flood is going to rival the devastating floods of 1927, I figured that talking rivers would be timely.

Since the 18th Century, a series of levees have been built in an attempt to mitigate flooding and maintain the river's flow. The Mississippi is an old river, which shows characteristic features- fast moving water will erode portions of the riverbanks, and the sediment will be deposited in areas of slow moving water, changing the course of the river by forming bends in the river called meanders. The accumulation of sediment and a change in the main current of the river can "cut off" meanders and form oxbow lakes (known in the drouthy Antipodes as "billibongs"). The water course of an old river has a natural tendency to change, which poses some problems for shipping- in 1963, the Old River Control Structure (who said ORCS weren't real?) was built in an attempt to prevent the Atchafalaya River from "capturing" the flow of the Mississippi and shifting the main watercourse in the Delta.

To compound matters, the Mississippi River forms an extensive floodplain, which is considered desirable land- consequently, much of the land has been "sequestered" from the river by levees- along some stretches of the river more than 90% of the floodplain is behind levees. This combination of development on the floodplain and the "constriction" of the watercourse has potentially disastrous consequences. As Charles Ellet Jr warned in his report to Congress in the 1850s:

"The extension of the levees along the borders of the Mississippi, and of its tributaries and outlets, by means of which the water that was formerly allowed to spread over many thousand square miles of low lands is becoming more and more confined to the immediate channel of the river, and is therefore, compelled to rise higher and flow faster, until, under the increased power of the current, it may have time to excavate a wider and deeper trench to give vent to the increased volume which it conveys."

Naturally, Ellet was not heeded, and the construction of levees began in earnest.

What is the solution to this problem? Yearly floods are a reality in the region, and the increased intensity of storms will only compound the problem, and a paucity of funding will make mitigation of the problem more difficult. Could resettlement of floodplain residents be Constitutional, or even feasible? Would a shifting focus of plans, a move from riverbank levees to levees along the perimeter of population centers, be possible? The Army Corps of Engineers does incredible, heroic work, but does all this effort make sense in a long-term perspective? Can any organization, no matter how heroic, no matter how competent, constrain such a mighty beast as the Father of Waters? Perhaps it is better to acknowledge defeat, to recognize that struggling against nature is a fool's errand, and to take steps to work within the constraints imposed by natural processes.

It's often been said that "Mother Nature is a bitch"- yeah, she's indifferent to the insignificant organisms that build their homes on her corpus, blowing them away with a burp or smashing them to paste with a twitch. That being said, Mother Nature has nothing on human cruelty- just check out speaker of the Missouri house Steve Tilley discuss a decision whether to blow levees by Cairo, Illinois (a majority black town with a history of racial strife) or to blow levees protecting Missouri farmland:

I wish I knew who the laughing hyena was- to make a joke about a decision which a humane person would find agonizing is appalling. Yeah, they're only poor black people, so some monster could make light of the situation. As it turns out, the levee was breached to protect Cairo. The long-term management of flooding in the region, though, is an uncertain prospect, and nobody seems to want to make the hard decisions regarding this perennial problem.


ifthethunderdontgetya™³²®© said...

As Charles Ellet Jr warned in his report to Congress in the 1850s:

We learn some things, but some things we just don't want to learn.

Substance McGravitas said...

speaker of the Missouri house Steve Tilley

Holy shit what an asshole.

Dragon-King Wangchuck said...

Wait'll you see the Republican plan for the War on Flooding. Two hundred thousand cops will stand at the riverbank and simultaneously shoot the river until the flooding stops. All while yelling WOLVERINES! And also a tax cut.

Big Bad Bald Bastard said...

Two hundred thousand cops will stand at the riverbank and simultaneously shoot the river until the flooding stops. All while yelling WOLVERINES! And also a tax cut.

Nah, they'll just send this guy. WOLVERINES!!!

Anonymous said...

One minor point: the levees have made the problem worse in two ways. One is obvious: flood waters have nowhere to go, so the river rises faster. The other is hidden but worse: the sediment that would ordinarily be deposited in the flood plain remains in the river bed, raising the river's bottom. This is most clearly visible in New Orleans, where the river bottom is near street grade and the non-flood river top is above the streets. 'Twasn't so when NOLA was first built.

Big Bad Bald Bastard said...

That's hardly a minor point, old chum!

ButchPansy said...

Worrying about down-stream consequences is something politicians are not very good at.

E.J. said...

That's just not true. The river is approx. 200 feet deep at New Orleans so its bottom is nowhere near street-grade. Huge tankers and cruise ships could not operate here if the river were as shallow as you say. Most of the year, the top of the river is several feet below street grade.