What happened to New Orleans is terrible. But as James Robertson points out, it was not unanticipated.
The situation reminds me of our increasing understanding of earthquakes where I live in the Pacific Northwest. A similar hell could break out at any time here.
Jared Diamond's book "Collapse" addresses this recurring theme. A societal collapse is often triggered by an environmental collapse. These days the signs of a coming disaster are well known if not widely acknowledged, let alone acted upon effectively.