The problem for FEMA is that no one had conceived all 5 at once.
Literally, no one had imagined mass evacuation and civil unrest on water.....
Under this scenario, only two agencies are equpiped to such a rescue, the Navy and Coast Guard. But even they are limited, as they are equiped to rescue people in the dozens and scores, not in the hundreds of thousands.
The Coast Guard and the Navy were also deployed doing homeland security or warfighting duties. They have been retasked to help, but the numbers of ships are still in the dozens.
Air rescue also is possible, but also only in the score, as even the biggest transport helos only can hold 15 to 20 people.
Civil Unrest is handled by the Natioanl Guard, not the Coast Guard or Navy. There is no SOP for civil unrest in 20-30 feet of water. Personal water craft were commandeered in the last several days to perform grid searches on water, an unheard of effort for a major US city.
The repair of the levee is also the responsibility of the US Army Corp of Engineers, but this will take planning beyond the scale of imagination in stopping the lake form coming in. Sand bags stop rivers, not lakes. Plugging this hole is immense, some several miles of levee covered in 30-50 feet of water.
The civil unrest is subsiding as more assets have been brought to bear in this regard and as more people are directed to supplies of food and water. This will allow more rescue workers to enter the hot zone and extricate people to shelter and mass care, which may be some states away.
In the business of Emeregency Management, there are often groups called RED TEAMS, who try to concieve of possible or emerging disasters, so that teams can prepare for them. They work against BLUE TEAMS, who have to respond to red team scenarios. Points are kept between them for satisfactory or non-satisfactory responses.
Katrina would be a score for a red team.