Natural Hazards and Risk Perception: Snow Avalanches in Iceland

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Natural Hazards and Risk Perception Snow
Avalanches in Iceland
School of Geography FACULTY OF EARTH AND
ENVIRONMENT

• Chris Keylock

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School of Geography FACULTY OF EARTH AND
ENVIRONMENT

• Risk Analysis
• Investigating risks from natural hazards is an
  important task for engineers and geoscientists.
• It is one of the few areas of contemporary
  geographic scholarship where human and physical
  geography come together to study a phenomenon
  (although it has relatively little visibility in
  human geography curricula).
• It is an area that is popular with students and
  we have proposed in the past that it provides a
  suitable context for introducing first-year
  students to a suite of geographic techniques.
• It is generally conceived in a probabilistic
  manner and getting students to think in terms of
  probabilities is a useful training for
  undergraduate study and later in life.

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School of Geography FACULTY OF EARTH AND
ENVIRONMENT

• Risk Analysis
• Risk (expressed as the probability of death) can
  be defined as the product of three probabilities
• (1) The chance of an event reaching a particular
  location
• (2) The chance of somebody being in that
  location
• (3) The chance of an event killing that person.

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School of Geography FACULTY OF EARTH AND
ENVIRONMENT

• Risk Analysis
• (1) The chance of an event reaching a particular
  location - A statistical analysis of historical
  events to determine the number of events per year
  that reach a location.
• (2) The chance of somebody being in that location
  An analysis of population patterns and
  projections. (Note that this term is often
  ignored by setting it to 1.0).
• (3) The chance of an event killing that person
  An understanding of process dynamics (generally
  through numerical modelling) so that the exerted
  forces can be calculated for an event travelling
  a particular distance (given by (1)).

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School of Geography FACULTY OF EARTH AND
ENVIRONMENT
Flateyri, Iceland
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School of Geography FACULTY OF EARTH AND
ENVIRONMENT
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School of Geography FACULTY OF EARTH AND
ENVIRONMENT
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School of Geography FACULTY OF EARTH AND
ENVIRONMENT
Montroc, France, 1999
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School of Geography FACULTY OF EARTH AND
ENVIRONMENT
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School of Geography FACULTY OF EARTH AND
ENVIRONMENT
Mathematical models for the flow are then used to
predict local velocities and thus, probable
damage, which can be linked to loss-of-life. These
are based on shallow-water equations
(conservation of mass and momentum) with friction
laws that are considered appropriate (as well as
parameters for those friction laws).
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School of Geography FACULTY OF EARTH AND
ENVIRONMENT
Taconnaz, near Chamonix
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School of Geography FACULTY OF EARTH AND
ENVIRONMENT
Impact pressures are derived from the modelled
velocity data and can then be converted into a
vulnerability (v) where C2 and C1 are upper and
lower limits on the impact pressure where below
C1 no fatalities are expected and above C2 100
fatalities are expected.
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School of Geography FACULTY OF EARTH AND
ENVIRONMENT
The red zone in the Swiss avalanche zoning
criteria for dense snow avalanches is given by a
return period of less than 30 years, or if the
return period is between 30 and 300 years, then
the impact pressure must exceed 30 kPa. Thus,
with a return period of hundred years (0.01
chance of occurrence in a given year), and values
of 5 kPa and 100 kPa for C1 and C2, the value for
v of a 30 kPa event is 0.26 and the risk is 0.01
0.26 0.003 (assuming that a person is at the
location all the time).
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School of Geography FACULTY OF EARTH AND
ENVIRONMENT
Acceptable risk in Iceland is set at 0.00003.
Hence, an event such as that just described would
necessitate mitigative measures.
Flateyri, Iceland
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School of Geography FACULTY OF EARTH AND
ENVIRONMENT
Neskaupstadur, Iceland
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School of Geography FACULTY OF EARTH AND
ENVIRONMENT
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School of Geography FACULTY OF EARTH AND
ENVIRONMENT
Is this level of acceptable risk acceptable to
everybody in Iceland? Which groups perceive risk
to be higher? Does the general publics
understanding of the problem and the areas that
are most at risk agree with that of the
scientists? While it may be better scientifically
to employ one form of mitigative measure in one
place and a different form in another, how do
people perceive the effectiveness of different
defensive methods and the reason for choosing or
adopting such tools? Such questions are extremely
important for understanding social
conceptualisations of risk and for designing
acceptable strategies for ameliorating
risk. There is consequently, a need to talk to
people!
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School of Geography FACULTY OF EARTH AND
ENVIRONMENT
http//www.leeds.ac.uk/satsie