So, there is to be an enquiry into how Katrina was handled. Good.
However, it is a bad move for Bush to head it.
If the Whitehouse did not act properly, then the enquiry lead by Bush is unlikely to point the finger. Eventually people will find out.
If the Whitehouse acted properly, and the enquiry agrees, then people will suspect coverup. There will be nothing to find out, but people will keep digging.
Either way, it is a no-win scenario (not that this thing has any 'winners').
Sure, set up the enquiry, but make it truly independent, or this decision will come back and bite you, Mr. President.