If you are talking about Darwinian evolution by natural selection, um no. Most of the people who lived there during Katrina lived there because they grew up or worked there, so their reason for being below the water level was not blatant stupidity. Most of the affected areas were poor, and poor people have lower mobility levels (they simply don't have the money to move). The flood affected thousands of people regardless of their level of "survivability" or "fecundity", so it has nothing to do with natural selection. In fact, natural selection doesn't really operate on humans in the modern developed world any more because social factors like income and education level have a far great effect on survival and fecundity than any "natural" factors. Poor people in the third world are still subjected largely to natural selection though.