I suggest that you read this article, excerpt below:

http://www.boingboing.net/2011/03/22/how-people-really-be.html?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+boingboing%2FiBag+%28Boing+Boing%29

In her gorgeous book A Paradise Built In Hell: The Extraordinary Communities That Arise In Disaster, Rebecca Solnit shows how this is how almost everybody responds to disaster, across continents and across contexts. When power grids are destroyed and city grids demolished, social grids light up.

This is so cross-cultural -- from Haiti to New Zealand -- that it is probably part of an evolved instinct inherent to our species, and it's not hard to see why. We now know that 60,000 years ago, the entire human race was reduced to a single tribe of 2000 human beings wandering the savannahs of Africa. That was it. That was us. If they -- our ancestors -- didn't have a strong impulse to look out for each other in a crisis, you wouldn't be reading this now.

Yet there are a few examples stubbornly fixed in the popular imagination of people reacting to a natural disaster by becoming primal and vicious. Remember the gangs "marauding" through New Orleans, raping and even cannibalizing people in the Super-Dome after Hurricane Katrina? It turns out they didn't exist. Years of journalistic investigations showed them to be racist fantasies. They didn't happen. Yes, there was some "looting" -- which consisted of starving people breaking into closed and abandoned shops for food. Of course human beings can behave atrociously - but the aftermath of a disaster seems to be the time when it is least likely.

This information is essential for knowing how to respond to disasters. There is a fear that the Japanese government is with-holding information about the dangers of the nuclear meltdown because they don't trust the people to react sensibly and calmly. There is no way of knowing, yet, whether this is true. But understanding this crucial history should guide the government to tell the truth and trust the people. As Solnit puts it: "If you imagine that the public is a danger, you endanger the public."

That last sentence - that really sums it up for me, and succinctly puts my perspective on emergency planning and my direct experiences with emergencies into a single, easy to digest thought.