Seen in Insurance Journal:
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 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.
There are, of course, three major lessons to be learned:
- Always check your math.
- There’s a significant difference between addition and subtraction (the discrepancy was driven by a “minus” being placed where a “plus” should have been
- When people’s lives and life savings’ are at stake, it’s probably a pretty good idea for the government agency doing major work to release technical data and permit independent review.