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Katrina, the "man-made disaster"

NOLA has a round-up of the latest evidence pointing to the flooding being caused not by the hurricane so much as "operator error": incorrect design decisions by the Army Corps of Engineers and others. Commentary here. Keep us informed if we ever learn who's right.

"Engineers Fear Levee Repairs Not Enough"

From this:

Repairs to New Orleans' levees may be insufficient to protect residents moving back to the devastated city if another hurricane comes before the tropical storm season ends this month, expert engineers said Wednesday.
Dozens of breaches continue to mar the city's levee system, including a large seep at the Industrial Canal last week, according to engineering experts who have examined the floodwalls...
At the Industrial Canal levee, which abuts New Orleans' obliterated Ninth Ward, repairs to breaches "were not adequate for a high-water incidence _ for instance, another hurricane storm surge with the storm season that isn't yet behind us, or even a very high tide," said Raymond B. Seed. Seed, a University of California at Berkeley engineering professor, participated in a National Science Foundation study investigating the levee failures.
The large seep at that levee, which occurred Oct. 24, "was not entirely unexpected," Seed told the panel.
However, he said, deeper walls "that will be far more stable than they were before" have been dug in at least some areas since the NSF first examined the levees.
"I don't think there is a long-term risk to the city of New Orleans," Seed said...

For Seed's full findings, see UC Berkeley: " Investigators release preliminary findings of levee failures at Senate hearing"

MRGO as the "express lane": Part 2

Katrina may mean MR-GO has to go

...After massive flooding killed hundreds in St. Bernard Parish, eastern New Orleans and the Lower 9th Ward, there is growing consensus that Katrina's surge was made far worse by the Mississippi River-Gulf Outlet, a 76-mile shortcut between the city and the Gulf of Mexico. And while the shipping industry vows to protect the channel, political momentum appears increasingly in favor of St. Bernard officials who have long warned the waterway must be closed.
Scientists from Louisiana State University's Hurricane Center say the Gulf Outlet, also known as MR-GO, and a second channel, the Intracoastal Waterway, funneled Katrina's powerful surge into a narrow bottleneck just north of Chalmette.
The funnel caused floodwaters to stack up several feet higher than elsewhere in the metro area and sharply increased the surge's speed as it rushed through the MR-GO and into the Industrial Canal. As a result, levees that would have been topped -- but not breached -- crumbled under the hydrologic assault, turning a major flood into an unprecedented disaster, according to Hassan Mashriqui, a civil engineer from LSU who had predicted the funnel effect prior to the storm.
Absent the funnel effect, Mashriqui said, "you would have had maybe 2 to 3 feet of flooding at the max, but not everybody's house underwater. It's still flooding, but one is significant and one is catastrophic."
The Port of New Orleans and Army Corps of Engineers dispute the Hurricane Center's claims, saying Katrina's intensity was enough to topple levees regardless of the shipping channel. Those levees were built to withstand only storms up to Category 3; Katrina made landfall at Buras as a Category 4 storm.
"This was just a ferocious and huge storm," Port of New Orleans CEO Gary LaGrange said.

Previously: MR-Gulf Outlet canal under scrutiny; "express lane" for the surge

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