The usual chorus of some who believe they are following a biblical prophetic model can be heard pronouncing that Katrina was God's judgment on New Orleans.
Some facts they miss:
1) Biblical prophecy of doom almost always preceded the event of destruction in order to bring about repentance - rather than following it as a way of heaping abuse on those who have suffered.
2) This was the position of Job's friends who insinuated that his calamity was due to his sinfulness. They were wrong, God was angry with them for misrepresenting him, and ultimately Job was the intecessor for them.
3) When Jesus encountered those who were suggesting that the Galileans were slaughtered by the Romans because of their sinfulness, he turned the conversation back on those making such suggestions. He denied that these after-the-fact claims were right in asserting that the Galileans were greater sinners. Seems those making such accusation ought to heed Jesus' warning.