After Hurricane Katrina two years ago, the Army Corps of Engineers in New Orleans built a system of flood gates and pumps. Maps released on June 20 showed that in areas around the Lakeview neighborhood the system would reduce flooding by 5½ feet if there were a major storm. Unfortunately, that number turns out to be more than a little bit off: buried in a report released on November 7 is the prediction by scientists that in fact the system in those neighborhoods will reduce floodwaters by a mere 6 inches.
The reason for the maps being off by 1000 percent? Math errors. In one calculation, a plus sign was inadvertently replaced with a minus sign.
Equally notable is the fact that the mistake was caught by a reporter, not anyone associated with the project. According to the AP article here by Cain Burdeau
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.
It’s not yet known if the insurance companies will be awarding partial credit to homeowners because the calculations were very nearly correct.
Thanks to David Cox at Amherst College for bringing this news article to our attention!
Tags: Math in the News, Math Mistakes, New Orleans
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