Mistakes Made in New Orleans Flood Maps

November 19, 2007

A system of flood gates and pumps built since Hurricane Katrina to help alleviate flooding in several New Orleans neighborhoods may not be as much help as authorities first said.

The Army Corps of Engineers released flood risk maps on a block-by-block basis on June 20, but didn’t include some technical data, preventing independent assessments of the accuracy of the maps.

The maps showed that the improvements made to the city canals’ drainage systems would reduce flooding during a major storm by about 5.5 feet in Lakeview and nearby neighborhoods. The maps were based on a storm that has the likelihood of occurring at least once in 100 years.

But in a report released Nov. 7, Corps scientists estimated that the actual benefit the system would provide would be just 6 inches.

The discrepancy was tucked into the voluminous report’s appendices, and neither the Corps nor the scientists hired to conduct the study brought the changes to the public’s attention when the report was released. It wasn’t until New Orleans television station WWL-TV asked an engineer involved in the assessment about the discrepancy that it became known.

“We’ve made some corrections,” the engineer, Ed Link, told The Associated Press.

Link said the mistakes were apparently made in the calculations for two sub-basins that include Lakeview and nearby neighborhoods. In one, a minus sign was used instead of a plus sign.

Ivor van Heerden, a hurricane and levee expert with Louisiana State University, said the mistakes are the latest example of sloppiness and a lack of scientific peer review in Corps’ work.

“It’s peoples lives we’re playing with and all we’re getting is fuzzy science,” van Heerden said.

Walter Baumy, a chief Corps engineer in New Orleans, said he was unfamiliar with the mistakes, but said “I wouldn’t contest what Dr. Link says.”

But he added that the floodgates installed on the canals have given New Orleans “far superior” protection.

Donald Powell, federal coordinator for Gulf Coast rebuilding, said in a statement he was only informed of the errors in the maps on Nov. 16.

“Our team immediately contacted Dr. Link to express my strong concerns and my expectations on how the public will be better informed in the future. While the news is disappointing, it is an indication that the ongoing review process of the draft materials is working as intended.”

Other Corps officials would not comment on the mistakes or did not return telephone calls.

Tami Do, 46, said she and her family rebuilt in Lakeview because they felt the Corps was doing a good job. Now, she said, her faith is shaken.

“I have confidence in what they’re doing all along the levee, with the pumps. That’s one of the reasons we’re back here,” she said. “But these kinds of things put doubt back in your mind. If they got this wrong, what else have they gotten wrong?”

Her husband, Tommy Do, wondered if the mistake would mean an increase in insurance rates, or perhaps a change in building requirements. To get flood insurance people must build their homes out of the flood plain, and he wondered if those calculations might have to be re-calibrated because of the new data.

“Now all these people who have built these $300,000, $400,000 homes should be higher?” Tommy Do said. “That’s not good. We’re going to have to sue the Corps again!”

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