It is a rather difficult thing to prepare for.
A concerted program of civil defense and personal preparedness would go a long way. Homeland Security and FEMA should ideally be working on evacuation plans, mitigation, and recovery operations.
Responsible businesses and corporations should make prudent disaster recovery plans.
Individuals and families have an obligation to keep some emergency food,water, and necessities on hand. We also need to take responsibility to help ourselves and our neighbors.
Part of the whole Katrina disaster was the result of large numbers of people who had long ago surrendered their individual sovereignty to the state for the price of a AFDC check. Their response in a crisis was to wait for the nanny-state to take care of them and resort to criminality, looting, etc.
Americans used to be more prepared -- back in the 1950's. Some of us still are.
Fallout shelters; stocks of weeks worth of food, fuel, water (or adequate water filters) and other supplies; radiation detectors; potassium iodide tablets; guns & ammo; and other preparations which are cheap if done ahead of time.
Most of us will not be at ground zero (which we can't prepare for) but, instead, may be in a fallout zone or at least in an area affected by massive disruptions of utilities and other infrastructure services -- which we can prepare for.