huangyhg

new york times' editorial on floodwall in no...
september 22, 2005
faulty levees
the official explanation for the collapse of some of the flood walls protecting new orleans has been that hurricane katrina simply overwhelmed the system. but
reports yesterday in both the washington post and the new york times suggested that katrina might not have been as powerful as advertised and that the real
culprit was the system itself - flood walls so poorly constructed that they were easily breached.
this points a finger at either the army corps of engineers, which oversaw the design and construction of the flood walls, or congress, which appears to have
underfinanced the projects, or both.
corps officials have said all along that the system was not designed to protect the city from hurricanes larger than category 3, and corps spokesmen continue to
insist that katrina was a category 4 hurricane when it hit the gulf coast. but federal meteorologists now say that new orleans did not get the full brunt of the
storm, whose strongest winds passed dozens of miles east of the city. what's more, sustained winds over lake ponchartrain reached only 95 miles per hour, even
less than the winds of 111 to 130 miles per hour in a category 3 storm.
other research, meanwhile, has turned up serious weaknesses in the thinner and less stable flood walls built along the city's canal system beginning in the 1960's.
the failure of these walls - particularly along 17th street and london avenue - led to much of the devastation.
here again the research seems to contradict the official version, which is that extraordinary surges reached the top of or even "overtopped" the flood walls,
causing some sections to collapse. yet louisiana state university researchers doubt the water ever got that high. even if it had, they argue, it would have been
contained by properly constructed flood walls - essentially concrete slabs that resemble the sound barriers found beside highways.
a detailed analysis of the storm and of the city's defenses will take months. it is not clear, for instance, whether the flood walls' weaknesses were the result of
faulty engineering and shoddy workmanship on the corps' part or whether they resulted from congress's unwillingness over the years to provide enough money
and leadership to do the job properly. what is clear is that whatever investigation congress undertakes, either on its own or with outside counsel, it must meet
high standards of diligence and spare no one, including those in congress.
when i see some data in a prestigeous engineering or technical journal i will pay it some heed.
the nyt, and their editorial department, (but i repeat myself) long ago lost any credibility with me, and regarding them, if they say "a" i would almost automatically assume "b" to be true, but that is just my own opinion.
i'm from missouri on anything that they put forward.
rmw
vooter,
that's an interesting article and i hope that an accurate account of the science and engineering behind what happened will come out. in my opinion this is going to be difficult for most of us to do however, based on how we get information from the networks and print media in the us. i don't think the real story is going to come from the new york times or the washington post. i'm sure there will be some studies done by reputable organizations for the purpose of determining the suitability of current codes and design specs, and i will be more likely to believe what i hear from the engineering community rather than those with political motivations.
this is going to be interesting to watch. good topic.
regards,
-mike
politics aside, it was common knowledge since the 70's, that the flood walls (along the canals) were not storm resistant and as is common in louisiana had settled as much as 12-18" below the design elevation.
as usual it is not engineering knowledge or adice that is absent or lacking, but lack of priorities and political will.
having said that, it would have been a lot cheaper to improve the entire leevee system, than the trillion or so that it will cost to rebuild new orleans.
even after rita we have two more months of hurricanne season to go.
now that the levees have breached again pre-rita, the real and technical discussion of how to really 'fix' no should be real interesting.
the political spin will be just as interesting, and maybe even entertaining to those of us who are engineering professionals.
rmw
a relook at galveston would be instructive at this time. 100 yrs ago a sept hurricane killed 6000+ there and destroyed 1000's of structures including railroads. the massive reinf concrete seawall was constructed 15 high, and riprap was place at the sloping curved base. behind the wall, land reclamation was in the form of pumped sand slurry, which settled into firm land. houses were raised accordingly.
it's now time to do the job right and learn from past mistakes.

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