Daily Kos: Blew Holes: Why Levees Break

Blew holes.

Here's how it works, and what may well happen to New Orleans:

Water always moves. When it comes up against an earthen barrier its movement shifts from straight on or alongside the levee and is transformed into a swirling motion. Any variation in the levee -- a dip, a swerve, a slight indentation -- catches the swirling currents far below the top of the levee itself. The water swirls down there like a giant very efficient drill, weakening the levee from within. When it goes, it can do so quite suddenly; it "blows" a hole in itself and thus the name "blew holes," sometimes called "scour holes." These weaknesses are dastardly hard to identify before the water finds them first and by then it's way too late to do much about it.

Once the water on the high side starts rushing into the low side, there isn't anything any people, machines, or technology can do about it at the point of the breach until the two sides reach equilibrium.

I know nothing of the particulars of Lake Ponchartrain, nor can I guess when the breaches there will reach equilibrium. Unless they can break a hole that would drain more water in a different direction, water will continue to pour through that levee break into the city no matter if the pumps are working or not and regardless of how many 14,000 pound sandbags they can drop on top of it.

I can't speak to the political or economic machinations that caused New Orleans to cease its levee strengthening programs before they were completed. But 12 years ago I learned firsthand how levees work and how they fail, and I suspect that huge break near New Orleans happened similarly to what I described above. If Bush is responsible for redirecting money to his so-called war on terror that could have saved that levee, then he is responsible for the months and years of pain and misery wrought on Louisiana in this immediate aftermath of this most terrible storm, too.

When the water finally does quit flowing in, and after they are able to repair the breach and pump it all back out, and after they clear the millions of tons of mud, silt, and debris, they will find many of the wooden structures there thoroughly compromised and fit only for demolition.

Worst will be many of the oldest buildings built on old and crumbly stone or brick and mortar foundations. The old mortar will be saturated and mealy and in some instances washed out completely, leaving the foundations weakened beyond repair in many cases. That's what happened here. The flooded old buildings that were restorable after the flood were the oldest of the old, many barns and a few homes, that were built entirely of wood and set on stone pillars. Some of those "floated" a bit and could be jacked or moved back into place, but they survived. Most of the "newer" mortared brick and stone foundation buildings, save for some of the double walled cinder block commercial buildings, didn't make it.

Lots of things were different about our great flood. Except for a few catastrophic levee breaks that washed away whole buildings in a few seconds, most of us watched the water rise over many days and weeks. Some days it would creep up only a few inches, some days it would even drop a little, and other days it would rise a foot or two, just fast enough to watch it creep up the blacktop on the road where we banked our canoe each morning. But it took a long time; time enough for those whose homes and business were in harm's way to move their stuff to higher ground and watch in slow motion horror as their homes and farms were inundated and their lives were changed forever.

It's different in New Orleans. People are watching the water rise by several feet per day. And the mucky, smelly backwater that flooded us here in the heartland was nothing compared to what will flush itself into the poisonous soup filling a major city like New Orleans.

Life here returned to mostly normal a few years after the great floods of '93 and the nearly as great flood of '95. Bottomland farmers hired huge Cat tractors with 7 foot plowshares to turn under the six to 12 feet of sand that topped and nearly ruined the millions of acres of the world's most fertile soil. Today, the corn and beans and wheat are back where they were before in most places. I don't mean to underestimate the toil and expense and hardship we endured, but it will pale in comparison to rebuilding a major metropolitan area.

I love New Orleans. I've been there quite a few times and know people who grew up there and few who still lived there until this week. I fear it will never be the same again. Ever.

And that's just New Orleans. We are just now beginning to grasp the scope of the devastation in Mississippi. All this while our president golfs and plays guitar and pats himself on the back for the great strides for what he calls democracy, but smells like civil war, is making in Iraq. We must remember this and remind our friends and neighbors of it when he finally stands on some muddy rubble and tries to take credit for calling us together as a nation to mourn the loss of our Big Easy.

Daily Kos: Blew Holes: Why Levees Break


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