It indeed looks as though the levees were blown up in New Orleans. There were three spots which disintigrated, flooding 80% of the city. The storm wasn't the problem, nor was the tidal surge. Engineers have said that if water came over the top it would be spillage, not a catastrophic collapse, and these were concrete floodwalls that supposedly gave way while earthen berms that surround the city remained intact.

The residents heard muffled explosions (hate to link to this racist cretin but go with the news source you have, not with the news source you wish you had) - http://www.halturnershow.com/EarWitnessVideo.html">boom

There are a lot of reasons why the city was flooded, some more conjectural than others, but the city was indeed flooded. 1. Operation kill the niggers - for a long time due to factors not relevant to the situation at hand the city's population became increasingly black and increasingly poor. Sort of in the way for 2. Upscaling and gentrifying the city - developers and especially the gambling interests have been drooling to get on with their plans. 3. Psy -Op on the American people - Waiting those excruciatingly long days after the disaster to make the situation as bad as possible, then blaming it on local governments assures that in the event of new crises the people will scream in unison for the feds to show up. 3A. Added bonus - local governments are democratic. 4. Trial run for martial law - encircle the city with cops and military, media not allowed, hide the dead, and outsource the dirty work of pacifying the people with mercenaries from groups like Blackwater.("There are a lot of lessons we want to learn out of this process in terms of what works.
I think we are in fact on our way to getting on top of the whole Katrina exercise." –Vice President Dick Cheney, Sept. 10, 2005) 5. Operation inflate the poll numbers - worked big time after 9/11 but Rove must be off his game as the obvious deliberate mismanagement was siezed on by the media.

Or all the above.