Flawed Construction Key to Levee Failures
MICHELE NORRIS, host:
While preparations for Rita are under way, flood experts are still trying to figure out what happened after Katrina hit. They say early explanations for what caused New Orleans to flood appear to be wrong. The scientists now say Katrina did not push water over the top of the canal walls that run through downtown; the water simply never got that high. Rather, if the canal walls had performed as designed, researchers now say the downtown area might have remained dry. NPR's David Kestenbaum reports.
DAVID KESTENBAUM reporting:
Think of New Orleans as a fort surrounded by high walls. Engineers generally agree that the southeastern part of town and the neighboring area were flooded when a wall of water came over a long levee. But the situation has been far less clear downtown. Some canal walls broke there. Why? Early on, the US Army Corps of Engineers said the water had apparently risen so high that it flowed over the top of the canal walls and eroded the foundation. One engineer told NPR he guessed the water in Lake Pontchartrain to the north of town was perhaps a staggering 18 feet above normal. Paul Kemp, an oceanographer at Louisiana State University's Hurricane Center, says that now appears to be wrong. Last week, he and some colleagues got on a boat and went to the lake.
Mr. PAUL KEMP (Hurricane Center, Louisiana State University): We bring our boat into a launch that's about a half a mile west of the mouth of the 17th Street Canal. And, you know, when I look up, I see this beautiful continuous debris line about 200 or 300 feet long on the face of the levee.
KESTENBAUM: They got out a pole and determined that the high water line was not 18 feet above sea level, just 12 or 13 feet. Kemp got closer to the 17th Street Canal, the one that broke and allowed water into downtown. They went into an apartment.
Mr. KEMP: And we found waterlines inside the buildings there, and we measured the elevation of those and they were around 10 feet.
KESTENBAUM: If so, the canal walls should have been able to handle the water; they are 14 and a half or 15 feet high. A spokesperson for the Army Corps of Engineers told NPR early on that an eyewitness had seen water flowing over the top of the 17th Street Canal. But Kemp says if that were true, you would see erosion all along the base of the wall. He went there yesterday--the area had finally be pumped dry--and the ground looked fine, no evidence of a waterfall. He concludes that the wall the broke just broke somehow.
Mr. KEMP: It's frustrating, you know, because it looks like the flood protection, you know, should have been adequate.
KESTENBAUM: The Washington Post, which ran a story on the team's work this morning, quoted former Congressman Bob Livingston from Louisiana as saying, quote, "I don't know if it's bad construction or bad design, but whoever the contractor is has a problem," end quote.
At a press conference today, the Army Corps of Engineers said that many things are still fuzzy about the time just after the hurricane passed through. The Corps' David Pezza says engineers still think the wall's failure could have been caused by water going over the top.
Mr. DAVID PEZZA (US Army Corps of Engineers): That's the popular theory, but I can't confirm that because we haven't had an opportunity to really look into what happened.
KESTENBAUM: The Corps, he says, has mostly been dealing with getting water out of the city and bracing for Hurricane Rita. Soon, he says, they will begin a full forensic review of the flood protection system.
Mr. PEZZA: We call it an after-action review, which is what we do on every one of our projects to understand what happened and are there any lessons learned.
KESTENBAUM: The investigation into what happened will involve computer models, and some of the preliminary work is already under way. Johannes Westerink at the University of Notre Dame works on the main computer model for studying hurricane flooding. He's been simulating Katrina, and it also finds that downtown might have escaped flooding.
Mr. JOHANNES WESTERINK (University of Notre Dame): Actually, the water actually recessed and didn't over--in the simulations, didn't overtop the levees. In our simulations, the northern levee systems did not get overtopped.
KESTENBAUM: And the high water mark in the all-crucial canal that broke?
Mr. WESTERINK: Roughly, according to our simulations, about 12 feet above mean sea level.
KESTENBAUM: Just where Paul Kemp saw the high water line in the lake, a couple feet below the top of the canal walls. Westerink stresses that these numbers are rough. The Corps says it expects to get its postmortem under way soon. It expects the investigation will take eight months. David Kestenbaum, NPR News.
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