A few questions about Katrina, New Orleans, and terrorism

The readers of this blog seem to collectively know the answer to just about any question we can think to pose. So here are some questions:

1) How much of the damage/human toll is because of the hurricane per se versus the levees breaking? If we had perfect foresight, would 1,000 well-placed national guardsmen and some heavy machinery have been enough to save the levees?

2) If terrorists had thought of this first, could they have achieved the same effect as the hurricane, except more devastating because the attack would have come with no warning?

3) If so, are there other potential situations like this out there where a terrorist with a few explosive devices could cause such ruin?

4) Would the initial rescue response have been different if the victims weren’t poor and black?