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Lecture Note Hazard.pdf


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Hazard and Resource

Average
Extreme

Hazards
Critical Value

Resource
Critical Value

Event

Hazards
Extreme

Time

Since the earth is a highly dynamic planet, most natural events show a wide range
of variation through time in the use of energy and materials for environmental processes.
The outer limits of this behaviour we call ‘extremes’ and certain statistical measures,
notably magnitude-frequency relationships, are used to describe such extremes. But
extreme natural events are not considered as hazards unless they cause large-scale death
or damage to humans.
Hazards, therefore, result from the conflict of geophysical processes with people.
This interpretation gives humans a central role. First through location, because it is only
when people, their possessions and what they value get in the way of natural processes
that a risk of hazard exists. Second, through perception, because humans place subjective
judgments on natural processes as part of a general environmental appraisal whenever
they settle and use land. In other words, many hazardous processes merely represent the
extremes of a distribution of events that, in a slightly different context, would be regarded
as a resource.

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