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. (more…)