Thursday, April 10, 2008

River rising

Everybody's talking about the rising Mississippi River and the levees that keep it in check. And I'm not just talking about in the coffee shops and beauty parlors of New Orleans; my office is intense with activity.

It's called a flood fight, and with good reason.

When the water gets this high, even though reliably forecast to peak several feet lower than the tops of the levees, the weeks of water pressure and velocity on the levees will take their toll. As in any battle, troops will be deployed and defenses will need to be reinforced as the fight goes on. In 1973, I understand there were two locations where the main levee was showing signs of considerable stress, so a backup levee was constructed to keep the river at bay.

This is normal procedure. Cause for concern--yes. Cause for panic--no.

This is considerably different than a hurricane event. For one, the river is a well defined problem. We have mountains of historical data and a thorough understanding of how its waters flow. Hurricanes, to the contrary, are still very unpredictable. The National Weather Service has made huge strides in tropical cyclone prediction in recent decades, but it remains a game of odds. We don't have such gaps of knowledge when facing our foe in the Mississippi River. We know what's coming and when with great accuracy.

When a hurricane comes, all we can do is run away or hide behind levees. Again, a flood fight is different in that we can do much more. We have tools at our disposal--spillways that we can use to reduce pressure on our levees and divert the peak flows of the river.

Another difference is in how we conduct the fight. During the height of a hurricane it is simply not possible to closely monitor flood defenses or to attempt repairs. Even pump operators must take refuge in armored "safe houses" when the wind is at its worst. But the Mississippi River provides no such obstacle. Throughout the flood fight, inspectors will drive the levees and look for even the smallest indication of trouble. And when trouble occurs, crews will be able to respond quickly.

We can take solace in the knowledge that the river has not flooded the city since then: the levees have worked every time.

However, we must not let any of this lead us to be complacent. Just as we should never forget the hard lessons of 2005, we must always remember the suffering of 1927.

There's a reason it's called a flood fight. And the fight is on.


rcs said...

Tim, do you know if they've opened the River Control Structure to divert some flow through the Atchafalaya Basin? A friend who saw it in action in the late 90s said it was thunderous, you could hear it three miles away. I'd like to drive up and check it out before the river crests if so.

Tim said...

The Old River Control Structure is operated throughout the year to maintain a 30/70 distribution of flow between the Atchafalaya/Mississippi Rivers. When there are large floods, there is also a spillway gate called the Overbank Structure and an Auxilliary Structure. I don't know the details of what is going on up there. There's a pretty good presentation with lots of illustrations on how it all works here:



Leigh C. said...

A flood fight? Why am I now picturing John Belushi doing a Bluto in "Animal House" at the Spillway with all the carp coming outta the deluge from the opened structure?

dillyberto said...

I take much solace in knowing the brains and soul of you, sir, are in the fight.

and on our side!