Download Avalanche Hazard Destructive Potential

Avalanche Danger Scale
North American Development Work
Grant Statham, Mountain Risk Specialist
Since 2005 with the United States
• Who is it for?
• What comprises avalanche danger?
• What process is used in analysis?
The Problem with the Avalanche Danger Scale
• CONSEQUENCE is absent
• PROBABILITY terms are vague
• MITIGATION advice is weak
CONCLUSION . . .
• It is a poor evaluation and communication tool for
both professionals and the public
• Our forecasting and communication systems do not
fit within a modern risk framework
The problem is not just the danger scale, but also
the theory behind it
We require
1. Technical model for avalanche forecasting
(based on RISK THEORY)
2. Communication model for public bulletins
(based on the TECHNICAL MODEL and FOCUS TESTED)
Probability
RISK THEORY
AVALANCHE
HAZARD
Consequence
SNOW
STABILTY
RATING
SYSTEM
CAA, 2002
OGRS
Stability vs. Danger
Feb 8 - 11, 2006
Selkirk Mountains, BC
Avalanche Activity: The latest report of a large
deep slab avalanche was a size 4.0 from the
north face of Sifton that fractured 2-3m deep,
300m wide and ran on glacial ice. This
avalanche ran full path for 2 km including
500m over flat terrain.
STABILITY
DANGER
Fair
Considerable
Good
Considerable
Good
Moderate
Stability and Terrain Choices
COAST
Good
Good
Good
Stability and Terrain Choices
ROCKIES
Good
Good
Good
Terrain list – February 2003
Roger Atkins, 2004
Terrain list – February 2004
Roger Atkins, 2004
So where do we account for consequence?
• Professionals = Intuitive and discussion based
• Public = Buried inside lengthy text messages
What represents consequence?
• Avalanche size
• Avalanche character
Probability
AVALANCHE
HAZARD
Consequence
Lets start from the foundations of
avalanche forecasting
Decomposition
Probability
AVALANCHE
HAZARD
Consequence
Probability
AVALANCHE
HAZARD
Consequence
Probability
AVALANCHE
HAZARD
Consequence
Foundations
WEATHER
TERRAIN
SNOWPACK
AVALANCHES
CONFIDENCE
FORECASTING
ACTIVITY
SCALE
Cognitive, Inductive Reasoning
WEATHER
TERRAIN
SNOWPACK
AVALANCHES
CONFIDENCE
FORECASTING
ACTIVITY
SCALE
Probability
Sensitivity to
Triggering
Spatial
Distribution
AVALANCHE
HAZARD
Consequence
Discrete choices necessary
(subjective probability assessment)
Probability
Sensitivity to
Triggering
Spatial
Distribution
AVALANCHE
HAZARD
Consequence
Avalanche Size
Avalanche Character
Likelihood of Triggering
AVALANCHE
HAZARD
Destructive Potential
CONFIDENCE
Degree: Low → High
Factors:
•Anomalies
•Unusual events
•Unprecedented events or conditions
•Amount of data
•Quality of data
•Spatial scale
•Temporal scale
•Spatial variability
•Temporal variability
•Lingering instability
•State of knowledge
•Forecaster’s experience levels
Avalanche Hazard
Spatial
Distribution
Confidence
Triggering Likelihood
Sensitivity to
Triggering
Destructive Potential
Size
Character
Avalanche Hazard
Spatial
Distribution
Confidence
Conclusion
(activity specific)
Triggering Likelihood
Sensitivity to
Triggering
Destructive Potential
Size
Character
Avalanche danger rating is only a conclusion
Likelihood of Triggering
Conclusion and Communication
Destructive Potential
RISK THEORY
Probability x Consequence x Exposure = RISK
AVALANCHE RISK THEORY
Likelihood of Triggering x Destructive Potential
Avalanche Hazard
(danger scale)
AVALANCHE RISK THEORY
Likelihood of Triggering x Destructive Potential
x Exposure = RISK
Avalanche Hazard
(danger scale)
Public understanding requires more than just a
conclusion
Public understanding of avalanche danger
requires
• Better methods of describing forecasting processes
• Use of RISK THEORY as a framework for avalanche forecasting
• Consistent understanding and application by professionals
• Basis for public education and communication
Danger levels are only a communication strategy
THANKYOU!
Roger Atkins
Larry Stanier
Clair Israelson
Chris Stethem
Greg Johnson
John Kelly
Brad White
Ilya Storm
Bruce McMahon Bruce Tremper
Karl Birkeland
Mark Moore
Janet Kallem
Susan Hairsine
Doug Abromeit
Pascal Haegeli
Knox Williams
Alan Jones
Ethan Green
John Kelly