The levee on 17th Street in New Orleans shouldn't have broken.  While designed to handle a load of 14 feet of water, it never reached that and broke causing what is now estimated at $300 billion in damage.

According to the investigation, the engineering error was so obvious, so trivial that it should have been spotted and that it was not caught ultimately resulted in a significant percentage of the damage done to New Orleans from Katrina.

Read the whole thing.