See the text below that I read earlier this morning. Most of this is on the money in my book.
I'm reading American Dunkirk: The Waterborne Evacuation of Manhattan on 9/11 by James M Kendra and Tricia Wachtendorf.
"Scholars have struggled for precision in defining such concepts as disaster as well as related terms, including resilience, vulnerability, crisis, and recovery. They grapple, too, with the ideas of catastrophe and megacrisis; dozens of definitions exist for each of these terms (Perry 2006). This murkiness has real-world consequences for how high-level policy makers and street-level emergency managers make decisions about how and where to direct their funding and attention.
They affect how officials view the nature of a future disaster, and how they diagnose and respond to an unfolding crisis. None of the definitions for disaster is perfect. In many ways, those that depend most on numbers are least satisfactory. Take the number of fatalities or the amount of economic loss, for instance—each has a different significance based on the scale of society that is affected. For this reason, most scholars now hold a concept of disaster that contains an implicit sliding scale, where the magnitude of the impact is considered alongside the characteristics of the society that has experienced the event, including local capacity for response.
Nor can it be assumed that all hazards will have similar consequences. The decisions that people make for habitation, recreation, and commerce expose them to environmental extremes, influenced by historical conditions of social and economic development and by present efforts for planning and disaster mitigation (Mitchell 2003). For this reason, one sees different outcomes to earthquakes in Haiti and Chile, for example. The mismatch between natural, technical, and social systems (Mitchell 1990) creates conditions that make people more prone to harm. Disasters, in turn, result when the risk, which is a probability, is realized in an actual event. Nevertheless, all the definitions involve some notion of a social system being overwhelmed and unable to meet its needs, thus requiring assistance from elsewhere.
Some transformation of the natural and built environment occurs that leaves the area unable to provide its usual support for residents, workers, and visitors (Dombrowsky 1998). One particularly long-lasting concept of disaster describes it as follows: An event, concentrated in time and space, in which a society, or a relatively self-sufficient subdivision of a society, undergoes severe danger and incurs such losses to its members and physical appurtenances that the social structure is disrupted and the fulfillment of all or some of the essential functions of the society is prevented. (Fritz 1961: 655)