Corps of Engineers Report on New Orleans Hurricane Protection

[SlideRuleEra]

The US Army Corps of Engineers has release the final draft of "Performance Evaluation of the New Orleans and Southeast Louisiana Hurricane Protection System". Here it is

https://ipet.wes.army.mil/

...in nine parts (total of 1531 pages, 52MB of .pdf files) and a separate 32 MB zipped file of illustrations (.jpg files)

http://www.SlideRuleEra.net

 

[kenvlach]

For those w/o broadband, here's a 1-page summary:

"Army Corps of Engineers Admits Levee Defects Caused Flooding
By Ralph Vartabedian
[Los Angeles] Times Staff Writer
3:27 PM PDT, June 1, 2006

NEW ORLEANS — The Army Corps of Engineers acknowledged today that design defects in the levees protecting New Orleans caused the majority of flooding during Hurricane Katrina and that the disaster will almost certainly trigger reforms in how the federal government protects the American public.

The corps said that its 40-year effort to construct a hurricane protection system for the region of southern Louisiana had resulted in a set of piecemeal projects that "was a system in name only," a recognition that a wide range of errors, weak links and incomplete construction was at the heart of the massive damage that occurred on Aug. 29.

The corps released a 7,000-page investigation that is carefully worded and written in the language of government engineers, but delivers a stunning set of findings about errors made in the design of storm walls and earthen levees that failed during Katrina.

The report found that four major breaches of I-walls, a type of concrete storm wall that sits on top of an earthen levee, caused 65% of the flooding in the greater New Orleans area.

Although the report's executive summary never uses the words "design defect," corps officials said they now accept that their work had shortcomings and errors were largely responsible for the disaster.

"We do take accountability," Lt. Gen. Carl Strock, commander and chief engineer of the corps, said at a news conference in a downtown hotel, attended by five Army generals, the federal coordinator for Gulf Coast reconstruction and an assistant Army secretary.

The corps, Strock said, "is deeply saddened and enormously troubled" by the finding.

Strock said every section of I-walls will eventually have to be replaced because they proved ineffective during Katrina. The four breaches occurred when storm waters were several feet below the tops of the walls, meaning they had failed well below the maximum forces they had been designed to withstand.

The report also puts in the historical record a formal acknowledgment of the scope of the disaster, which killed 1,293 people.

"The flooding caused a breakdown in New Orleans' social structure, a loss of cultural heritage and dramatically altered the physical, economic, political, social and psychological character of the area," it said. "These impacts are unprecedented in their social consequence and unparalleled in the modern era of the United States."

Although many of the detailed technical findings had been released earlier in preliminary reports by the corps, the report contained a large amount of new information:

• Southern Louisiana is sinking much faster than generally recognized and levees were at substantially lower elevations relative to sea level than they were designed to be. In some cases, levees were 2 feet below their designed elevations. Moreover, the corps deliberately decided not to reexamine the problem, even as other federal agencies were recognizing the problem. My emphasis

• The city's pumping system, which provides the only way to remove water from a city below sea level, wasn't designed to operate during a major storm and that the impact of the flooding could have been reduced if the city had not lost its ability to pump water after Katrina. Because most of the region's pumps were inundated by the flood, it took 53 days to pump out the city, allowing the floodwaters to saturate and destroy structures.

• 25% of all the housing units in southern Louisiana were destroyed by Katrina. In New Orleans, the proportion is believed to be higher.

Strock said the repaired sections of levees are now the strongest parts of the system. The repairs were supposed to be completed by today, but are behind schedule by about two months. The enormous undertaking required heavy construction work on 169 miles of damaged or destroyed levees.

Although the breaches caused most of the flooding, a significant part of the Katrina damage occurred because the storm was larger than the system was designed to resist.

While wind speeds had dropped sharply by the time the hurricane hit New Orleans, its power over the Gulf of Mexico had created the largest ocean surge to ever hit the North American continent, the report said."

http://www.latimes.com/news/nationw...,0,1627317,print.story?coll=la-home-headlines

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Another study, in Nature, 1 June 2006, reports that parts of New Orleans are sinking even faster than reported above. Satellite radar shows some areas are sinking faster than 1 inch per year. Some levees were as much as 3 feet lower (vs. sea level) than when constructed 3 decades ago.

'The scientists name overdevelopment, drainage and natural seismic shifts as the main causes.
"My concern is the very low-lying areas," said lead author Tim Dixon, geophysicist at the University of Miami.
"I think those areas are death traps. I don't think those areas should be rebuilt," he said.'

http://news.bbc.co.uk/2/hi/americas/5035728.stm

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Forget about reconstruction in the low-lying areas, use as a source of fill material to raise other areas*, and convert to wetlands for wildlife habitat.
*such as where government is requiring homes to be elevated 3 -5 feet above grade to qualify for insurance.