Overtopping vs. Breaching

A major Republican talking point in response to the Katrina briefing video released this week by the AP has focused on the distinction between "breaching"--as in the Bush statement to ABC that nobody anticipated the levees breaching--and "overtopping", the word used by National Hurricane Center head Max Mayfield in the briefing video. And on Friday night the AP issued a clarification that focused on the conflation of those two terms, much to the joy of the right-bloggers.

But those two terms have been confused for months, ever since the Army Corps of Engineers first reported that the cause of the flooding of New Orleans was the overtopping of levees. We later learned that the 17th St. floodwall had breached, and later independent forensic analysis showed that it had never been overtopped. But the confusion was situational: while the 17th St. floodwall breached, other levees in the area, to the east, were overtopped.

Can we now turn to another area of repeated concern, the delay in calling for mandatory evacuation of New Orleans? Both the embattled Ray Nagin and outside observers like Mayfield have cited a reason for the timing: the need for phased evacuation of Southeast Louisiana, letting surrounding parishes closer to the coast evacuate first. Critiques of the evac that I've seen don't even engage this concept, let alone refute it. The fact appears to be that almost everybody who could or wanted to evacuate New Orleans did so; the problem was with those who couldn't or wouldn't.