INTRODUCTION AND PRINCIPLES Flashcards
Natural Hazard
An Earth process that is a potential threat to
human life or property
Natural Disaster
A hazardous Earth process that occurs over a
limited period of time in a defined area and significantly affects
people or property
Catastrophe
A massive disaster that requires a significant
expenditure of money and time for recovery
Important Principles in the Study of Natural Disasters
-Different hazards are often associated/linked with each other
-Hazards that in the past produced disasters now may produce catastrophes
-Risk analysis is an essential component of our ability to deal with natural disasters
-Hazards are predictable and understandable
-The consequences of hazards CAN be reduced/minimized
Different hazards are often associated/linked with each other
One scenario that occurs almost yearly in California illustrates this principle. California has a distinct wet season and dry season climate. During the summer/fall dry season, the landscape may become extremely parched and subject to wildfires (disaster #1). The wildfires burn away ground cover and damage the soil structure. When heavy rains
arrive in the subsequent wet season, the ground has no protection from raindrop impact and the soil is unable to absorb enough moisture. The
result is flooding, erosion, and landsliding (disaster #2, a direct consequence of disaster#1)
Hazards that in the past produced disasters now may produce catastrophes
*Climate change may be contributing to increasing size and frequency of
some disasters
*There are many more people (and homes/property) in the way of natural
hazards every year.
Risk analysis is an essential component of our ability to deal with natural disasters
*risk is based on the probability of an event and the likely damages
*risk analysis is critical in decision making regarding natural hazards
Hazards are predictable and
understandable
Long-time application of the
scientific method to studying Earth
processes has generated an
excellent understanding of how and
where natural disasters occur.
The consequences of hazards CAN be reduced/minimized
By applying (c) and (d) above, we can understand and even predict
hazards: so that we can take specific actions:
*land-use planning
*hazard resistant construction
*hazard modification (example flood management)
*forecasts: watches and warnings
*disaster preparedness
Why do people live in risky areas?
Natural
-Natural Service Functions
-Human foibles
-
Natural Service
Functions
The city of Grand Forks,
North Dakota is an
example of where
people took advantage
of natural service
functions of rivers (water
supply, efficient
transportation, fertile
soils) and also put
themselves at risk for
flooding. Figure shows
Grand Forks during the
flood of 1997.
Human foibles
-People’s attention is easily
distracted by day-to-day
activities. They have short
memory for issues that they
are not constantly
reminded of, particularly
unpleasant things. The
tsunami aftermath shown
below is partly the result of
poor preparedness, even
though a similar tsunami
had occurred just 14 years
earlier.
-People are poorly equipped
cognitively to assess risks
correctly. We are well adapted
to immediate emergency
dangers (being chased by a lion)
but poor at thinking far ahead
and planning for seemingly
abstract dangers in the far future.
Another common human
characteristic is optimism bias.
Optimism bias is often
paraphrased as the “It won’t
happen to me” effect.
The Magnitude-Frequency Concept
The larger an event is, the less frequently it occurs - in technical
terms, magnitude is inversely proportional to frequency
*Small events are common
*Large events are rare
Predicting’ Disasters
It is usually not possible to actually predict disasters - rather
scientists and emergency managers make statistical
assessments based on the historical occurrence of events
Recurrence interval
The average time interval between events of a certain size (magnitude
