Disasters affect lots of people in different ways so relief providers must have tools and techniques for assessing a wide variety of needs people may have.
For many groups, the top priority immediately after a disaster takes place is fulfilling the needs of individuals and groups affected by the event. This requires identifying what the needs are, acquring the resources needed to meet those needs, deploying those resources and determining whether of not a need is fulfilled so the next set of needs can be tackled.
There are many channels through which needs information can flow, and having a way to collect and action information from each of those channels will ensure you're getting the most and best information possible.
One of the best ways to collect information from people affected by disaster is via door-to-door canvassing of residents. Finding and training volunteers and asking the right questions of residents will be keys to a successful canvass.