New Orleans Still at Risk, Army Data Show

After nearly two years of work, the Army Corps of Engineers revealed yesterday which New Orleans neighborhoods and blocks were the most vulnerable to flooding, and which were the best protected. The report shows that despite considerable improvement, large swaths of the city are still likely to be flooded in a major storm.

Skip to next paragraph Multimedia Interactive Map New Orleans Flood Vulnerability Related Interactive Map nolarisk.usace.army.mil Hurricane KatrinaGo to Complete Coverage »

If a big hurricane were to hit today - producing flooding with a 1-in-100 chance of occurring in any year - parts of the Gentilly and Lakeview neighborhoods, in the northern half of the city, would probably still take on at least eight feet of water. Hundreds of flooded homes in those neighborhoods are being rebuilt by owners struggling to return.

But the report shows that the vulnerable areas within those neighborhoods are much smaller than they were before Hurricane Katrina - considered a 1-in-400 storm - thanks to the corps' substantial improvements to the 350-mile levee system, the floodwalls, pumps and gates.

As part of the report, the corps established a Web site, nolarisk.usace.army.mil, that allows New Orleans residents to study the city on a block-by-block basis and learn what kind of damage they might expect with more than 150 kinds of storms. If it works as promised, the system will allow residents to determine the relative risk of living in the various neighborhoods of New Orleans - and whether nearly two years and billion have made them safer.

The report clearly shows that some areas are less vulnerable than they were in 2005. But it could also potentially lead insurers and investors to think twice about supporting the rebuilding efforts in vulnerable areas or in the city as a whole.

Maj. Gen. Don T. Riley, the head of civil works for the corps, said in an interview that local leaders were initially wary of the report and how it would be used, and that some said, "Oh boy, I'm not sure we can do this - because we're trying to get people to move back in." But, he said, "after we worked with them and showed them, they said, ‘this can really be a good tool for planning.' "

The analysis of the city's risk, more than a year behind schedule and still a work in progress, is an enormously ambitious attempt to figure out just how risky it is to live in New Orleans, and is the first time the corps has released such a tool to the public anywhere in the nation. The Defense Department's supercomputers analyzed scores of different storms, estimating wind speeds, storm surges and pathways and how they would affect every street in the city.

Some of the risk to New Orleans has been reduced, largely because of the construction of enormous gates across the mouths of the city's three main drainage canals, which significantly raised the level of protection. Elsewhere in the greater New Orleans area, where the hurricane protection system was restored but not upgraded in a major way, the probability of damage does not change nearly as much: large parts of the Upper Ninth Ward could be expected to have two to four feet of water in a 1-in-50 flood, then and now.

A flood with a 1 percent chance of occurring would leave much of the Garden District relatively dry, as it remained during Hurricane Katrina, although a smaller patch of the neighborhoods to the north would be likely to flood.

City officials said the new tools would help them plan the city's halting recovery. Edward J. Blakely, the hurricane recovery chief for New Orleans, said that while the maps show that "quite a bit of the city" remains vulnerable to storms, the dangers would diminish as further protection was built. Eventually, Mr. Blakely said, "the risks aren't going to be different from those of a city in Florida."

Karen Durham-Aguilera, the civilian director of the corps' Task Force Hope, a nearly billion hurricane protection system project in New Orleans and southeast Louisiana, suggested that the facts about New Orleans presented in the report were anything but bad. "This is good, because it shows a lowered risk," Ms. Durham-Aguilera said.

"There's no place where you can say the risk is absolutely zero," she added.

As voluminous as it is, the report will nonetheless seem incomplete to many in New Orleans. The corps is not releasing the data on how the system to protect against 1 percent floods will perform, although officials said Monday that that portion of the report would be ready within weeks. That is the information that many in New Orleans want, because they know that what they have is not adequate but they might be willing to gamble that a major storm will not hit before 2011, when the stronger system is to be in place.

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