RandFan
Mormon Atheist
- Joined
- Dec 18, 2001
- Messages
- 60,135
Overtopping happens when the storm surge brings the water level above the top of the levee. Water pours over the levee and gets into the city, where it remains until it is either pumped out or is absorbed into the ground (or evaporates). This can cause a lot of damage, but it is not catastrophic. New Orleans has huge pumps which presumably are used to pump out rain water, so a little bit of overtopping could probably be accommodated rather easily (although any roads or houses near the levees would be waterlogged). A breach means that the levee literally falls apart in a spot, which then widens as water rushes in. This results in the water level inside the city equalizing with the sea level outside within a matter of hours. You're probably talking at least 1,000 times more water in a breach than an overtopping. On top of that, it's impossible to pump the water out until the breach is repaired.
ETA: To answer your other questions, I think that nobody thought a breach was going to happen. It really shouldn't have. The levee was supposed to withstand a Category 4 hurricane, and I think Katrina was only Category 3 when it hit New Orleans.
ETAM: The wiki link.
I'm at a loss.
FEMA placed a hurricane hit on NO as one of it's most pressing concerns. Yes or no?
Katrina attained Category 5 status on the morning of August 28 (it was not predicted to decrease).
Given these facts I don't understand your argument.
We got lucky when the hurricane lost force.
We got unlucky when the levee's breached.
No harm no foul.
AIU, the Levees were built for a cat 3 hurricane but they were not properly maintained.
Army Corps Is Faulted on New Orleans Levees
An organization of civil engineers yesterday questioned the soundness of large portions of New Orleans's levee system, warning that the city's federally designed flood walls were not built to standards stringent enough to protect a large city.
The group faulted the agency responsible for the levees, the Army Corps of Engineers, for adopting safety standards that were "too close to the margin" to protect human life. It also called for an urgent reexamination of the entire levee system, saying there are no assurances that the miles of concrete "I-walls" in New Orleans will hold up against even a moderate hurricane.
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