The results of hurricane Katrina and the tsunamis in Southeast Asia indicate that people will be left to their own devices whenever a really big disaster takes place.
A few years ago the destruction of a whole city was a tale of past wars and fiction stories about nuclear bombs in the hands of mentally unstable individuals, but natural disasters such as hurricanes and tsunamis that originated around the world quite recently indicate that national alert systems and rescue groups will not be enough neither to prevent such catastrophic events, nor cope with the enormous problems that surge as a result of them.
Indeed: City or region-wide catastrophes can happen. Hydro meteorological disasters are becoming more common. They have happened and they will continue to happen, just considering the effects of nature; and to that we should add the potential danger of massive terrorist attacks and suddenly, such mass destruction scenarios become almost a reality.
And despite pending political issues and opinions about what governments do or don't do when confronted with such huge dangers there is a reality: almost all emergency services around the world, be them bad, regular or good, have been designed considering smaller scenarios. Even the fall of a bridge, the crash of an airliner or an explosion at an oil refinery are much smaller than the kind of scenarios that we should now prepare for.
Fire brigades, police units, red cross volunteers, public hospitals and so on are simply not able to cope with bigger problems than what they were trained and equipped to deal with. Moreover: there is no way in which a public safety network able to respond efficiently in front of a catastrophe that has affected a whole city because to maintain such a structure would be extremely costly.
And to this, the political dimension should be added to: Experience around the world shows that whenever a big disaster takes place, politicians will enter in a series of deals and quarrels to determine who will be responsible for paying the damages before they order anyone, any organization like FEMA, the Army or whatever, to help the survivors.
So the only way to prepare for such events would be to think reallistically and think in creative ways such as adapting the concept of reserve troops used in countries like Israel and Switzerland, but for civilian uses: people should be trained to form part of their own local emergency units because whenever a big disaster strikes, hospitals, fire brigades and the other components of the current 911 services will certainly be overstretched and unable to attend a lot of people.
When you think about survival you should consider the worst possible scenarios, and that means that your government will desert you when the time comes. If they don't do that then your life will be easier, but if they do, you will be left stranded on your own.