If you look at scholarship on the origins of the state as an institution -- and there's been a lot of it, mostly based on archaelogical evidence -- it's pretty clear that there were three fucntions of government that convinced people to band together under formal institutions (optimistic historical interpretation) or to accept authoritarian rule by an aristocratic elite (pesimistic, and probably accurate interpretation). Those state roles were:
- Ending the pervasive communal violence that pervaded prestate societies (see some of the scholarship in murder rates)
- Flood control
Flood control, tied to irrigation, played a role in state formation in Mesopotamia, and one of the functions of the Egytian state was to help manage the effects of the annual flooding of the Nile with (the Egyptians developed geometry to keep everyone's landholdings straight).
In fact, one of the mythical Chinese culture-hero emperors, I think it was Yu, had as is accomplishment the taming of the Yellow River floods through control measures such as dykes. The Chinese were also big fans of the pathetic fallacy (that events in the natural world such as earthquakes and floods are directly linked to political events in the human world). The more rationalist Chinese philosphers said that this was actually because in a well-ordered state disasters would have a smaller impact because the response would come quickly. And if the dykes were well maintained -- no floods.
George W. Bush and his crew didn't seem much interested in flood control before Katrina, and they didn't seem much interested in making a rapid response afterwards. As a result, the catastrophe is much worse than it had to be. I think this may explain the visceral, and almost uniformly negative popular and media response to the administration's handling of the crisis: at a subconcious level (and I'll avoid getting too Jungian here) I think people realize that flood control and helping people after disasters are two of the fundamental functions of the state, and Bush has clearly bobbled the ball, if not dropped it down the sewer.
And frankly it's not relevant whether Bush knew about the problems with the levees: either he should have known, or he should have had someone in charge of that area of responsibilty who was competent and adequately funded. It's a federal responsibility and ignorance ain't an defense.