I see that President Bush was, in fact, briefed on the potential seriousness of Hurricane Katrina, thus casting a less-than-helpful light on his "Whoda thunk that could happen?" defense of his administration's complete lack of action until days after the disaster.
I also see that the Republican talking point has emerged: that briefing referred to the levees being "overtopped" (meaning water flowing over them), rather than the levees being breeched (meaning the levees rupturing and allowing water through them). That's an interesting attempt to salvage the President's honor, but the fact is, the overtopping of a water barrier can still lead to the ultimate failure of the barrier, and with it, utter disaster.
The apparent idea that "overtopping" would have represented a substantially lesser threat to New Orleans, well, doesn't hold water. (Pun intended.)