Basically if you can keep the windows and roof on your home you will survive. But if you don't get supplies to people within a short time they will begin dieing. That is where FEMA has made their mistakes. Time is too critical to wait to organize a plan, then put together truck convoys, and establish centralized food and water distribution points. That plan takes several days to execute. Hundreds of people are dead in New Orleans because of that plan.
There is absolutely no technical reason why pallets of food, water, tarps, cheap plastic umbrellas, and first aid kits couldn't be dropped by C130 aircraft within a few hours after the storm has passed. Drop one pallet every few blocks throughout the city and people will be able to survive for several days. They may not be comfortable but they will be alive when the ground convoys can reach the area.
After last years hurricanes in Florida FEMA had plenty of opportunities to learn from their mistakes but they did nothing. That is criminal negligence and the leadership should be indicted for felony manslaughter.
The flood arrived and the rest is history.
The true storm damage hit Mississippi and Alabama.
People can survive many days, or weeks without food, not so many without water. I'm as perplexed as you as to why bladders of water were not dropped into areas where survivors were congregating. But I think that the local or state governments are responsible for preparing for such a contingency (you know, communities of people choosing to live in a particular area). Blaming the federal government for the problem is a sheer liberal, big government, cradle-to-grave dependency that addles the American spirit, capability and morale. Oh, and by the way, is a road to ruin.