Assessing risk considering chances and uncertainties What is Probability A strong likelihood or chance of something dictionarycom The likelihood of something occurring or the chance of something happening yourdictionarycom ID: 914348
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Slide1
Probabilistic Risk Analysis
Assessing risk,
considering chances and uncertainties.
Slide2What is Probability?
“A strong likelihood or chance of something” (dictionary.com)
“The likelihood of something occurring or the chance of something happening” (yourdictionary.com)
Slide3What is Uncertainty?
“Unpredictability; indeterminacy; indefiniteness” (dictionary.com)
“Doubt” (yourdictionary.com)
Uncertainty (from limitations of data, models, or calculations) lower our confidence in our conclusions. (Environmental Protection Agency, 2014)
Slide4Risk and Probability
Risk is the probability of a hazard occurring
Risk cannot be exactly determined because the occurrence of a hazard is not guaranteed
Risk is estimated using reliable data: historical records, population statistics, geographical surveys, etc.
Probabilistic Risk Analysis/Assessment (PRA) refers to the use of probability to evaluate risk.
Slide5Risk and Probability – Flood Example
Flood recurrence intervals – ways to communicate the probability of a flood occurring
“100-year flood”
Myth: flood that occurs once every 100 years
Reality: flood that has a 1% chance of occurring any year
Same applies for 500-year (1/500 = 0.2% chance), 1000-year (1/1000 = 0.1% chance), etc.
(Brown et al., 2018)
Slide6Risk and Probability – Flood Example
Flood Insurance Rate Maps (FIRM)
Maps created by FEMA to management/mitigate floodplains and provide insurance information
Information reveals which areas could be affected by heavy/frequent floods
Determines insurance premiums
(Federal Emergency Management Agency, 2019)
Slide7Introduction to Probabilistic Risk Analysis (PRA)
Analytical approach that incorporates probability and uncertainty into risk assessment
Determines how risk varies among different population segments
Determines key influencers of uncertainties/variabilities
(Environmental Protection Agency, 2014)
Slide8Basic PRA Methodology + Examples
Methodology
Examples for Application
Identify risky scenario
Understand mechanism
Estimate frequency
Determine consequences
Driving through an intersection
Crossing the street (jaywalking)
Playing a competitive sport
Breaking curfew
Gambling
Going outside during a storm
Slide9Benefits of PRA
Provides information about the uncertainty of the data, models, scenarios, etc. used in risk assessment
Estimates the degree of confidence in a decision
Estimate the trade-offs in different risk management options
(Environmental Protection Agency, 2014)
Slide10Why Use PRA?
Identify essential risk factors and prioritize them
Design controls specific to those risks
Be aware of uncertainties and variable factors
Optimize decision-making
improve risk management
(Shah, 2004)
Slide11PRA For Decision-Making Assistance
Identifies weaknesses in complex systems
Enables and prioritizes improvement
Compare different strategies by various metrics
Designed to consider any/all possible failures
Could reveal hidden surprises
Could provide unforeseen alternatives
Slide12Example: CAPRA
CAPRA: Comprehensive Approach to Probabilistic Risk Assessment
Computer application used for risk assessment/mapping
Includes software modules for various specific hazards
Analyzes past statistical data to simulate hazard intensities and frequencies
(Cardona et al., 2012)