putting people and risk in the same picture via hazard ensemble diagrams tim lutz dept. of geology...
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Putting people and risk in the same picture via hazard ensemble diagrams
Tim LutzDept. of Geology & Astronomy
West Chester UniversityWest Chester, PA
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GSA’s position statement on Natural Hazards (2008):“Geoscientists have a professional responsibility to inform the public about natural hazards and the need to build an increasingly natural hazard-resilient society, thereby enabling more responsible actions and decisions.”
National Research Council’s report on flood risk reduction (2000):“Identifying sound, credible, and effective risk reduction priorities and solutions depends greatly on a well-informed public. The public should be knowledgeable about risk issues and should be given opportunities to express opinions and become involved in risk assessment and risk management activities.”
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Tarbuck & Lutgens, 2011
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National Flood Insurance Program (NFIP)
Flood Insurance Rate Map (FIRM)
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Mean = median = mode = 100 years
Default concept:Probability decreases symmetrically around the mean
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Mean = 100 years
Median = 69 years
Mode = 0 years Recurrence interval distribution predicted for independent random events (exponential distribution)
Standard deviation = Mean(e.g., 100 years ± 100 years)
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Series 1
Series 2
Series 3
Series 4
Series 5
Five series of random events; average recurrence = 100 years
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Series 1
Series 2
Series 3
Series 4
Series 5
Five series of random events; average recurrence = 100 years
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Example: USGS 05331000 Mississippi River @ St Paul, MN (114 years of record)
Twin Cities 7 Metro map.png by Davumaya (2008), provided by Wikimedia
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The inverse of a magnitude-exceedance probability model can be used to simulate annual peak flows
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An ensemble is a set of simulations which together define the distribution of most probable outcomes conditional on exposure.
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Unwarranted pessimism
Unwarranted optimism
Weighing of risks
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Top of right bank levee in S. St. Paul (29 ft)
Flood walls deployed at St. Paul airport (17 ft)Flood stage (14 ft)
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Annual peak flow history Magnitude-frequency model
Magnitude-frequency model Flow ensemble
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Flow ensemble
+Rating model =
Stage ensemble
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Generalization
History of hazard Magnitude-frequency model Ensemble diagrams
Straightforward extensions
•Seismic hazard Gutenberg-Richter model Ensemble diagrams
•Volcanic hazard VEI1-based m-f model Ensemble diagrams
•Nuclear hazards INES2-based m-f model Ensemble diagrams
1 VEI = Volcano Explosivity Index2 INES = International Nuclear & Radiological Event Scale
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For more information about hazard ensemble diagrams, check out Lutz, 2011, JGE v. 59, pp. 5-12; and email me ([email protected]) for an Excel file that can generate ensembles from annual peak flow data.