This is, unfortunately, unprecedented. A plan that would have been appropriate to deal with an Andrew or Camille level of destruction would have been woefully inadequate to deal with the current situation in LA/MS.
It may be that they actually did have a plan, but that plan completely fell apart when it ran smack into no communications, no access, the loss of key transportation routes, and a scope of disaster that was off the 'bad' end of the scale for any reasonable planning.
By way of comparison, we've heard for four years now about DHS planning for a N/B/C attack. But if a nuke went off in a major US city than is already beset by transportation choke points (i.e. NYC, Seattle, SF), do you really think that the response 3 days later is going to resemble a well-oiled machine?
Nope. See Jeffe's excellent post 106 at the beginning of this thread.
No, but I know the response of the members of the press in the White House Briefing Room will be very well-oiled.