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Could gates, not floodwalls, have blocked storm surge?

From Many decisions led to failed levees:

It was a simple solution that could have prevented one of the worst disasters in the nation's history: metal gates at the mouths of New Orleans' canals that closed automatically to block hurricane storm surges on Lake Pontchartrain.
But the gates were never built. Local officials objected to the Army Corps of Engineers' plans in the 1980s, saying they would interfere with the city's antiquated network of pump stations that drain rainwater from the city.
The broken levees that flooded New Orleans after Hurricane Katrina have their roots in decades of decisions like the one to abandon the floodgates. The decisions reach all the way to Washington, where Congress in 1992 ordered the Army Corps to abandon the gates and instead build the network of flood walls that failed, according to Al Naomi, a corps senior project manager.
One of four teams investigating the levee failures told the Senate Homeland Security Committee on Wednesday that some preliminary indications of the levee failures are beginning to emerge, but it's still too early to say what caused the massive breaches.
A USA TODAY analysis of government documents and interviews with investigators, public officials and independent engineers shows that the underlying reasons for the flooding are compromises that undercut safety, miscalculations that underestimated risk and poor relations between the patchwork of agencies that oversee the miles of flood walls around New Orleans.
...Critical problems that underlie the failures behind the most costly flood in U.S. history:
• The 40-year-old analysis that served as the basis for how big to build the levees badly underestimated the potential for a large hurricane to hit the city.
The Army Corps of Engineers opted in 1965 to protect against what it believed would be the worst storm in 200 years. Congress agreed. Ivor Van Heerden, the leader of a Louisiana investigative team examining the levees, says that at least two larger hurricanes other than Katrina have hit New Orleans in the past 100 years.
By contrast, the Netherlands decided to protect itself against the worst storm possible in 10,000 years after more than 1,800 people died in a massive levee failure in 1953.
• New Orleans' levees - the result of the city's gradual growth rather than safety or efficiency - are riskier than those in neighboring communities.
Jefferson Parish, which adjoins New Orleans to the west, relies on a simpler system of levees at the lakefront to keep high water out. The levees are higher and stronger than the levees that failed on New Orleans' drainage canals.
As a result, Jefferson remained dry during Katrina.
• Safety is compromised by the patchwork of governmental agencies and private firms that share responsibility for designing, building and maintaining the levee system.
Investigators found numerous leaks where two sections of levees controlled by different authorities joined, says Peter Nicholson, a civil engineering professor from the University of Hawaii who heads a levee investigation by the American Society of Civil Engineers.
The problem is symbolic of a broader issue that has undercut safety over the years, say the investigators: Safety is too easily compromised because no single agency is in charge.
"You have multiple agencies, some of which aren't on speaking terms with each other," says Raymond Seed, another Berkeley professor who heads the investigative team from the National Science Foundation.
Just as the gates at the mouths of the canals were opposed by local levee and pumping agencies, environmental groups in the 1980s derailed plans to erect a structure to block storm surges from Lake Pontchartrain. Engineers now say that undercut safety.
• Investigators found signs that poor maintenance of levees had compromised safety.
Bea says he believes large trees allowed to grow near levees may have contributed to the failures. Investigators say they also found leaks caused by portions of levees that had sunk and not been repaired.
• The corps, which oversees levee design and construction, has steadily lost expertise in the face of budget cuts. That's "as shocking as what happened in New Orleans itself," Seed says.

Several tipsters: shortcuts used in building levees

Here's more on yesterday's Congressional testimony by Raymond Seed, who heads up a National Science Foundation team conducting a review of the levees and the floodwalls:

Several of the levees that flooded New Orleans may have been built with shoddy materials or by contractors who took shortcuts to save money, [Seed told Congress].
About a dozen people, including engineers and contractors, made the allegations of poor workmanship in recent weeks to investigators probing the levee failures, [Seed said].
The complaints focus on two canals where levees topped with flood walls were built in stages over the past 15 years. One of the claims is that contractors used steel sheets - which were driven into the levees to prevent water seepage - that were shorter than what was called for in designs. If true, that could have made the levees weak and prone to failure.
Other tipsters complained that inferior materials, such as porous soil, were used to construct the levees.
Robert Bea, another University of California, Berkeley professor working with Seed, said in an interview that he talked on the phone with two women who said they had specific information from their late husbands on construction shortcuts taken on the levees.
Seed said other investigators received similar complaints...

"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"

UC Berkeley: " Investigators release preliminary findings of levee failures at Senate hearing"

Here's their press release:

Many of the New Orleans levee and floodwall failures in the wake of Hurricane Katrina occurred at weak-link junctions where different levee or wall sections joined together, according to a preliminary report released today (Wednesday, Nov. 2) by independent investigators from the University of California, Berkeley, and the American Society of Civil Engineers (ASCE).
Raymond Seed, UC Berkeley professor of civil and environmental engineering, and Peter Nicholson, an associate professor of geotechnical engineering at the University of Hawaii, presented several findings at a hearing this morning in Washington, D.C., before the Senate Committee on Homeland Security and Governmental Affairs. Seed is the head of a team investigating the levee failures with funding from the National Science Foundation and the UC Berkeley-based Center for Information Technology Research in the Interest of Society (CITRIS), and Nicholson is head of the ASCE geotechnical team...

The full report is in this 12.9 Meg PDF file.

ACE redesigns floodwalls to be stronger

WASHINGTON -- The Army Corps of Engineers is planning to repair New Orleans area levee breaches caused by Hurricane Katrina with fortified walls much stronger than the originals, design documents show.
Where some floodwalls -- consisting of a concrete section mounted on a steel base -- collapsed, the corps wants bulkier concrete walls and significantly deeper steel anchors reinforced with concrete piles.
Corps officials say the new designs are intended to compensate for structural weaknesses caused by the breaches -- and for uncertainty over the strength of the original designs.
"At this time, we haven't fully understood the failure mechanisms at all of these locations," said Walter Baumy, chief of the engineering division of the corps' New Orleans district...

They're putting out bids for this this week, and the cost will be around $400 million. This is part of their plan to restore protection to pre-Katrina levels in time for the 2006 season.

Reason for levee failure discovered?

From this:

Soil tests indicate that a soft, spongy layer of swamp peat underneath the 17th Street canal floodwall was the weak point that caused soil to move and the wall to breach during Hurricane Katrina, an engineer who has studied the data says.
"The thing that is remarkable here is the very low strength of the soils around the bottom of the sheet pile" base of the floodwall, said Robert Bea, a geotechnical engineer at the University of California, Berkeley, who examined the test results. Bea is a member of the National Science Foundation team that is studying the levee system's performance during Katrina.
Bea said other data shows the same peat layer also runs under the London Avenue canal breaches and probably was instrumental in the collapses there as well.
Investigators are focusing on the 17th Street and London Avenue canal levee walls because, unlike other parts of the system, they were apparently not topped by Katrina's storm surge. That could mean a design or construction flaw is to blame for the collapses - and for the flooding of much of central New Orleans...

Levees, floodwalls, seepage, heaving, sand boils background info

Here's a site that appears to have Army Corps of Engineers and related engineering reports for sale (levees, seepage). I don't know if they're available directly from ACE for free. And, the reports go back several years.

The Federal Government through the U.S. Army Corps of Engineers (USACE) has a large investment in flood-control levees. Where such levees are built on pervious foundations, seepage beneath the levee (underseepage) during floods can produce pressure and flow conditions capable of initiating subsurface erosion leading to levee failure. Two adverse phenomena may occur; one is sand boils which involves the movement of subsurface sand to the surface by flowing water, and the other is heaving which involves the upward movement of a relatively impervious surface layer resulting from subsurface water pressures in excess of its weight. To prevent such occurrences, the USACE has developed a set of procedures to analyze underseepage conditions on a site-specific basis and a set of procedures to design underseepage control measures. For the most part, these procedures were developed in the 194Os and 1950s. Intensive construction of control measures was accomplished in the 195Os and l96Os. Several moderately large and major floods have provided data from which the validity of the procedures and the security of the constructed system can be inferred. Also, since the 195Os many technical advancements have been made in engineering analysis techniques and construction methods that may merit application to underseepage problems.

Jackson, ACE on the Industrial Canal and the barge

From this:

[Jesse] Jackson believes a big barge crashed through the floodwall here [Industrial Canal], bringing the tidal surge into this neighborhood, causing the devastation.

According to Ernest Murry from the Army Corps of Engineers, everything - including who owns the barge - is still up in the air. The barge has an ID #, but they don't know why it was there during the storm. And, from Murry: "My theory is the barge came through after the wall fell".

The Army Corps of Engineers said the sheet pilings for the flood wall on the Industrial Canal were driven 20 feet deep. That's what engineers specified to protect the area from a category-3 hurricane.
As crews continue to make repairs, Murry said he thinks water came over the top of the floodwall, undermining the levee.
The Army Corps of Engineers said it does not know who owns the barge that came crashing through the neighborhood during Hurricane Katrina.
"It eroded all the ground on the backside of the wall and then the wall just collapsed over," Murry said, pointing out one of two breaches on the east side of the Industrial Canal.
But why, Jackson asked, was that barge in this canal as a category-4 hurricane made landfall?
"When they anticipate a hurricane coming, don't they move barges further away from the possibility of this kind of collision?" Jackson said as Murry nodded in agreement.
When the barge did come through, Murry said it landed on top of some homes.
"Actually, it was about 30 feet over…during Katrina. And then when Rita came through, it floated through again and came over this way," he said.

Previously: Did a barge cause the Industrial Canal breach? and Did barges cause the floodwall breaches?

Beeb tries for Brown, FEMA scoop and fails

The BBC will be showing a doc called "The Hurricane That Shook America", and they promote it in Fema 'knew of New Orleans danger'.
There appear to be two slightly newsworthy bits of info:

a key briefing officer within Fema sent a message directly to Mr Brown early on the day before Katrina hit, warning him of potentially disastrous flooding in New Orleans, which could trap more than 100,000 people.

I'm pretty sure Brown knew that was a possibility. The question is what details were provided and the major question is what happened after the floodwalls/levees failed. Was there specific information in the memo that Brown did not act on? Recall he wanted a mandatory evacuation. Perhaps the memo should have been sent to Blanco, and a few days before the storm.

Walter Maestri, head of emergency preparedness for Jefferson Parish, told the BBC that Fema officials promised emergency teams from the area that they would supply food, water, medical provisions, and assistance with transporting evacuees from the city - all within 48 hours of the emergency.
In the event, these emergency teams were left without the help they asked for.

Is that news?

Ivor van Heerden, an expert on hurricanes from Louisiana State University, told the BBC that local officials had taken the predictions of the Pam exercise rather more seriously than their federal counterparts.

Covered by Sixty Minutes a few weeks ago.
As for the headline of their story, obviously everyone knew the levees weren't built for a Category 5 storm.

Engineers blame shifting barriers, not overtopping

From "Engineers: New cause of New Orleans flood":

Much of the city flooded not because water rushed over the tops of levees, but because two of the storm barriers that ring New Orleans actually shifted and then collapsed, a team of independent engineers said Friday.
The preliminary analysis contradicts initial reports by the U.S. Army Corps of Engineers, which said water may have pushed over the top of the levees, eroding the earthen embankments that support the flood walls.
The independent engineers said the shifting of the barriers was understandable and did not assign blame or speculate about design flaws that the storm surge from Hurricane Katrina may have exposed.
"Levees tend to be built in very difficult situations on poor site conditions because you're essentially turning marshy land into land you can stabilize and do things on," said civil engineering professor Raymond Seed, who led a team from the University of California at Berkeley.
The California team worked with the American Society of Civil Engineers and Army engineers for several days this week before releasing the findings. More research is planned.

And, the Army Corps of Engineers says:

Soil giving way beneath the flood walls, causing the walls to collapse, was "certainly a possibility," said Paul Mlakar, a senior research scientist with the Corps.

See also:
Soil heaves, structural problems caused flooding, not overtopping?
ACE backtracks on levee conclusions
Sinking, bad design caused floodwall failure?


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