So what you are saying is, the State of Louisiana is in charge and legally responsible for ALL efforts of rescue, emergency health matters and shelters, security, evac and so forth to date. Not FEMA? I am just asking for a LEGAL clarification between state and federal.
FEMA Notice of Fed. Major Disaster LA Katrina
The relevant governing law, the Stafford Act, can be found here -
I do not find any differentiation in levels of declared emergencies, once one exists, nor any subsequent trigger reserved to the state level. The state does have exclusive authority over the Guard and there are limits on Fed use of military personnel to support civilian authorities.
The LA state declaration is here, in PDF -
There have also been 5 LA executive orders related to Katarina, which can be found at the bottom of this page. They related to things like keeping police officers on duty, requesting buses and hotels rooms, and the like.