A response to a disaster is something which comes instantly since we have no clue what will happen in the next moment. Disaster can be natural or accidental, like floods, earthquake, forest fire, rail accidents, road accidents even a disaster can be epidemic and so on. But we can't just sit and wait for a disaster to come and devastate everything. We need to have proper planning to stop the disaster which is impossible (for natural disaster) but for accidental disaster, yes we can stop it or avoid it or prevent it or decrease the effect of disaster. Proper planning   and having caution signs and danger signs at necessary places. There should be steps which should be performed and practised so that we can act accordingly during disaster. However there are emergency situation also which should be wisely and instantly performed and for this kind of situation also we perform some activity.

Another variable that is not often addressed (most infamously in the Katrina debacle) is coordination between federal, state, and local relief efforts, not to mention private relief efforts. I've experienced a number of hurricanes in my life, and often that is the biggest problem--organizations that all want the same thing are often working at odds with each other. Relief efforts are massive undertakings, and they require a high degree of coordination.

I agree with both ideas above that there should be a plan and that the plan might not work out as intended.  It is important to include in each plan some sort of flexibility.  Often, emergency plans are more about who will be in charge and how decisions will get made quickly instead of actual scripted responses.  A fully planned response will be quick, but it might not be able to account for all the variables involved in a real emergency.  A plan for who will be in charge or where people should report to will have a slower reaction time but it will be able to deal with all the components of the current disaster.  In truth, real disasters are unpredictable.  All we can do is try to be as prepared as possible and hope for the best.

The main problem with any contingency plan is that there are so many variables when it comes to disasters. In many ways, no two disaster are the same. In light of this, you will not be able to plan for everything. So, if agencies and people plan as best as they can and have a means to communicate to people after a disaster, this might be the best approach. 

The big problem with creating sets of contingency plans to address different types of emergency situations is that disasters often do not follow the assumptions upon which such plans are based.

As I write this, parts of the east coast of the United States are trying to recover from extensive damage caused by high winds and torrential rains roughly one week ago. The direct result of the storms was large numbers of people and businesses that lost electrical power due to damaged trees breaking transmission lines.

A contingency plan for removing the downed trees, replacing damaged electrical poles, restringing electrical lines, and restoring power exists, I'm sure. It may or may not, however, have addressed the difficult of getting to some of the areas that are affected by road damage or flooded roads as a result of the rains. And I'm sure the plans didn't figure in record-setting high temperatures for multiple consecutive days, which has certainly made the working conditions for repair crews much more difficult!

Plans are important and needed, but we need to understand that Mother Nature can be bigger than any plan when she wants to be...

Having a set of plans which outline different types of emergency responses based on the type of disaster at hand seems like one way to create a situation where emergency response can be accurate and quick.

For instance, there may be one response plan for a nuclear disaster and another for a hurricane and another for an extreme rain storm. 

If, instead of a set of distinct contingency plans, there is simply a list of groups responsible for responding to a disaster, those who are called on may be prepared to respond but unaware of what action(s) to take.