L2 : Foundations for Hazard Risk Assessment Flashcards
3 Components of risk assessment
Identification
Analysis
Evaluation
Define risk identification
Recognise and describe the risks (may be associated with a single hazard or multi-hazards) and the scope of the assessment
Define risk analysis
Understand the nature and sources of the risk and estimate the level of risk (a quantitative or qualitative calculation of H, E, V and risk)
Define risk evaluation
Compare risk with risk criteria (acceptable, tolerable, unacceptable)
What are the main components of hazard analysis?
Frequency/magnitude relationship, initiation process and travel or transmission of hazard
What are the 6 scales of assessment for different hazards?
Global Continental/large countries National Provincial Municipal Community
What are statistical models? (empirical, black-box, empirical-statistical) Method: Data: Assumption: What can they be used to determine
Method: Derive a statistical relationship between observed hazard drivers and resulting hazard event. Hazard modelled using statistical relationship to transform inputs to outputs.
Data: observed hazard events with associated triggers (probabilities) and system properties (prep factors)
Assumption: repeatability and stationarity of the system (past is key to future). Only applicable in similar settings
Used for hazard magnitude frequency curve (probability). Cumulative probability curves, use distributions.
What are physically based models? (deterministic or grey/white box models)
Method:
Method: hazard processes are explicitly represented by physics-based equations solved using numerical modelling (e.g. FE)
Data: measured physical parameters of the system
Assumptions: the model and input data describe the physical system
In reality env systems can never be fully defined, use a mixture of measured and empirical inputs calibrated against obs –> grey box
Other types of hazard model (4)
Qualitative - info evaluated and analysed verbally based on judgement
Quantitative - info is recorded analysed and evaluated used numerical scales and techniques
Heuristic - experts use indicators/decision rules to assess hazard on semi-quantitative indices
Stochastic and probabilistic - input param values sampled from prob distribution, model run multiple times with different input values to represent full parameter space and account for the effects of uncertainty
Spatially distributed - implemented in Geographical Information Systems
Sources of model uncertainty (6)
1) Aleatory
2) Epistemic (system dynamics)
3) Epistemic (forcing and response data)
4) Epistemic (disinformation)
5) Semantic/linguistic
6) Ontological
2 methods of attributing value to human life
Human capital method:
Based on an individual’s lost future earning capacity in the event of accident or death. The life of a child has the highest value; zero value for people who are unable to work.
Willingness to pay approaches:
Measures risk aversion in terms of how much people would be prepared to pay to avoid a certain reduction in their chance of accident or premature death. Assessed by questionnaires.
Aim of risk management?
Bring risk levels down to societally and economically acceptable, or at least ‘tolerable’ levels. Cost-benefit analyses used to prioritise risk reduction resources. Principle: make risks As Low As Reasonably Practicable (ALARP).
In a risk assessment we first….. and then……
Identify the hazard scenario of interest - can be individual events or different hazards caused by the same event (cascades)
Then select the modelling approach depending on hazard type, purpose of assessment, scale of analysis and data and model availability.
Define aleatory uncertainty
Inherent randomness of the system. Uncertainty with the stationary statistical characteristics (natural variation). May be structured but can be reduced to a stationary random distribution
Define epistemic uncertainty (system dynamics)
Define epistemic uncertainty (system dynamics)
