In characterizing hazards there
are a number of indicators, and these tend to be related:
(1) What is the range of potential magnitudes and
intensities that you may experience?
(2) Is there a time, day, season, or other factor that
constrains when this type of event can happen.
Earthquakes happen at any time of the day, but mass fatality
school shootings happen only when
students and staff are in the school buildings.
Can we identify the duration of the event, including pre-event,
event impact, and diminishing after-impacts?
Is there a timeline for how the hazard turns into an actual
(3) Can we identify the physical extent of the impact zone?
Floods inundate their flood plain; therefore, the parts of the
community within the flood plain are in the hazard impact zone.
Examine hazards in neighboring localities to determine if their
impact zones cross into your area.
(4) How frequently does the hazard develop into an actual
event? Frequencies, even if only
approximate, become probabilities for decisions under conditions of
risk. If none can be established,
another key to prediction is the presence of prodromes (signs that a
disaster may be imminent). For
example, in human systems failures, delayed or
nonexistent maintenance is a standard sign of increasing
potential for accidents.
(5) Finally are there are related hazards (for example,
tropical cyclones in North America are known to generate relatively weak
tornadoes)? And can the hazard
create a cascade of other hazards and impacts as it progresses (serial
dam failures are an example)?