Usually, a disaster is a local event. Consider using a contact point outside of the affected area. We have several reliable friends in various parts of the country. If we become seperated, we try to contact the first person on the list. This may be difficult in the first hours of an emergency, but after several days some form of communication will re-appear. It sure beats relying on the local authorities to help you find your family when there are many shelters and many many people.