And YRHT notes that the debate between overtopping and breaching is, well, not a debate because a catastrophic flood can be caused by both:
I mean, doesn't even a second-rate mind understand that overtopping might lead to a breach? Doesn't even a fool understand that massive overtopping from storm surge-- even if the levees held-- would have similarly catastrophic results?But let’s play their game, shall we?
Those defending Bush’s “I don't think anyone anticipated the breach of the levees” statement point to Max Mayfield warning:
"I don't think any model can tell you with any confidence right now whether the levees will be topped or not but that is obviously a very, very grave concern," Mayfield told the briefing.Then they say:
But this has nothing to do with the levees breaching; it has to do with them being overtopped--a much less dangerous threat.Okay. I would agree that overtopping has the potential to be a “much less dangerous threat.” For example, submerge a styrofoam cup into a big pot full of water until the water line almost reaches the top of the cup. The inside of the cup stays dry because it is protected by the sides of the cup. Now make some waves. The water will overtop the cup and accumulate at the bottom. But, once the waves stop, the water stops accumulating and the cup doesn’t fill up.
Now, break the side of the styrofoam cup. The water inside the cup levels off with the water outside the cup. That’s what happened when the levees breached. Lake Pontchartrain leveled off inside New Orleans. That’s a much more dangerous threat than just a little water accumulating in the lower areas of the city.
So, they say, that’s what Bush was talking about. He expected overtopping but not breaching.
Sounds like a good defense, doesn’t it? Not to the Army Corps of Engineers:
Immediately after the storm, corps officials speculated the breached walls had been overtopped. It was the most logical explanation, because water rushing down the land side of the walls would have quickly eroded the levee supporting the walls. Robbed of that critical support, the walls would have been unable to hold the weight of water that reached to the top of the 14-foot walls.That’s exactly what happened in St. Bernard and Plaquemines Parishes and with the Industrial Canal.
But it would take a lot of water to cause such erosion and scouring – like from the storm surge of “the big one” maybe? Did anyone say we should be preparing for “the big one?”
Yep. Michael Brown did:
"This is, to put it mildly, the big one," Brown said.So Bush says they weren’t anticipating the breaching of levees but he sat there and listened to his people say they were anticipating the type of storm surge that could cause overtopping of levees which would lead to breaching.
This makes the difference between overtopping and breaching a moot point. The type of overtopping they thought would occur would have caused the breaching they didn’t anticipate.
What’s sad about all this is that Katrina wasn’t “the big one” or the “worst case scenario” for New Orleans. But, given the poor construction of the levees and the bungled rescue, it might as well have been.