A More Effective Handling Of Post-Disaster Scenario

Why do we keep the victims of a calamity in the affected region itself, without evacuating them from the same? (I have noticed that the evacuation usually takes place only if there is any threat of further calamity). Isn’t it better to take them away to a place where they can have a more-or-less normal life, only to bring them back when the restoration process has brought back the affected region into normal condition? More