levees

Bahamonde: saw levee break on Aug 29; Chertoff: didn't learn until Aug 30

According to Bush Adviser Acknowledges Lack of Preparation for Katrina, on the night of Monday August 29, Marty Bahamonde reported to Michael Brown that "he had observed a massive break on the Lake Pontchartrain levee [the 17th Avenue Canal levee] and flooding over 80 percent of the city". Brown told Bahamonde that he would call the White House, but Chertoff denies that Brown told him that.

"The tenor of his discussions on Monday . . . was, this was bad, but it could have been worse," Chertoff said in an interview, adding that he learned of Bahamonde's report only after meeting him personally days later. "There was not a report to me until the following morning that there was a significant breach of the 17th Street levee."

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.
From "Performance of Levee Underseepage Controls: A Critical Review" by the ENGINEER RESEARCH AND DEVELOPMENT CENTER VICKSBURG MS GEOTECHNICAL AND STRUCTURES LAB:

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?

The "levees" vs. "floodwalls" distinction

As I've been trying to point out, when the media refers to "levees" in some cases they're refering to floodwalls. Now, from the It-takes-a-DUmmie category comes this picture-heavy thread showing the difference and the distinction between them.

ACE backtracks on levee conclusions

From "Ground Shifted Beneath Levees":

...Within days of the flooding, federal engineers asserted that the flood-control system was simply never designed for such a powerful storm.
Now, with evidence suggesting Katrina's intensity fell within the range the levees should have handled, corps spokesmen are saying the organization wants to conduct a full-scale analysis of the design and construction of the levees.
The levee system was designed to withstand a Category 3 hurricane. Katrina's winds had weakened to 125 mph by the time it reached New Orleans, consistent with a Category 3 storm, according to meteorologist Chris Landsea of the National Hurricane Center in Miami.
Surges from the Gulf of Mexico and Lake Pontchartrain spilled over the walls at the 17th Street Canal, London Avenue Canal and the Inner Harbor Navigation Canal, say Army officials and experts at the New Orleans Sewerage and Water Board, which operates the city's pumping stations.

Syndicate content