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Risk Analysis

Risk Analysis. By Cees van Westen westen@itc.nl. Objectives. Understand the procedures for loss estimation; Carry out a qualitative risk assessment combining susceptibility and vulnerability; Carry out a quantitative risk assessment using risk curves;

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Risk Analysis

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  1. Risk Analysis By Cees van Westen westen@itc.nl

  2. Objectives • Understand the procedures for loss estimation; • Carry out a qualitative risk assessment combining susceptibility and vulnerability; • Carry out a quantitative risk assessment using risk curves; • Use GIS for risk assessment for different hazard types; • Use GIS for multi-hazard risk assessment for buildings and population; Risk = The probability of harmful consequences, or expected losses (deaths, injuries, property, livelihoods, economic activity disrupted or environment damaged) resulting from interactions between (natural, human-induced or man-made) hazards and vulnerable conditions in a given area and time period.

  3. Definitions Risk Assessment is the process of making a decision recommendation on whether existing risks are tolerable and present risk control measures are adequate, and if not, whether alternative risk control measures are justified or will be implemented. Risk assessment incorporates the risk analysis and risk evaluation phases Risk Analysis deals with the use of available information to estimate the risk to individuals or populations, property or the environment, from hazards. Risk evaluation is the stage at which values and judgment enter the decision process, explicitly or implicitly, by including considerations of the importance of the estimated risks and the associated social, environmental, and economic consequences, in order to identify a range of alternatives for managing the risks

  4. Multi hazard risk assessment

  5. Qualitative versus quantitative risk Qualitative risk analysis methods: No quantification of the probability of losses. Also called relative risk Quantitative risk analysis methods: Quantification of the probability of losses. Also called absolute risk • Risk matrix approach • Indicator based analysis • Spatial Multi-Criteria evaluation Important aspects: Single/ multi hazard Direct/indirect loss (in) tangible loss Losses by sectors (financial, housing, social, agricultural etc) Individual/societal • Simple risk overlay • Deterministic (scenario based) • Probabilistic: • Includes all possible scenarios • Includes uncertainty • Includes chain effect /domino effects complexity Risk = Hazard * Vulnerability * Amount of elements-at-risk

  6. Qualitative risk assessment • Risk matrix • Define probability classes • Define loss classes • Define the combination of the two as risk classes • Alternatively: define risk matrix with vulnerability and hazard classes

  7. Qualitative risk assessment Qualitative_risk = Qualitative_risk [Susceptibility,Vulnerability] Vulnerability Two dimensional table Susceptibility ISL 2004

  8. Risk indices: Disaster Deficiency Index (O.D. Cardona) The Disaster Deficit Index measures country risk from a macroeconomic and financial perspective according to possible catastrophic events. MCE loss = Maximum Considered Event Economic resilience is a composite index which is made by combining 5 indicators: • Insurance and reassurance payments (F1p) • Reserve funds for disasters (F2p) • Aid and donations (F3p) • New taxes (F4p) • Budgetary reallocations (F5p) • External credit (F6p) • Internal credit (F7p) E is the economic value of all the property exposed; V( ) is the vulnerability function, which relates the intensity of the event with the fraction of the value that is lost if an event of such intensity takes place; IR is the intensity of the event associated to the selected return period; FS is a factor that corrects intensities to account for local site effects; and K is a factor that corrects for uncertainty in the vulnerability function A DDI greater than 1.0 reflects the country’s inability to cope with extreme disasters even by going into as much debt as possible. The greater the DDI, the greater the gap between losses and the country’s ability to face them

  9. Risk indices: Disaster Deficiency Index (O.D. Cardona) The Local Disaster Index identifies the social and environmental risks resulting from more recurrent lower level events (which are often chronic at the local and subnational levels). The Prevalent Vulnerability Index is made up of a series of indicators that characterize prevalent vulnerability conditions reflected in exposure in prone areas, socioeconomic weaknesses and lack of social resilience in general. LDIk = number of deaths K LDIA= number of people affected A LDIL= economic losses Based on DesInventar database

  10. Risk indices: Disaster Deficiency Index (O.D. Cardona) The Risk Management Index brings together a group of indicators that measure a country’s risk management performance. These indicators reflect the organizational, development, capacity and institutional actions taken to reduce vulnerability and losses, to prepare for crisis and to recover efficiently from disasters. RMIRI = risk identification RMIRR = risk reduction RMIDM = disaster management RMIFP = governance and financial protection.

  11. Other risk indices • UNDP: Disaster Risk Index • PreventionWeb • Worldbank Hotspots project

  12. Quantitative Risk RS = PT * P L * V * A PT is the temporal (e.g. annual) probability of occurrence of a specific hazard scenario (Hs) with a given return period in an area; PL is the locational or spatial probability of occurrence of a specific hazard scenario with a given return period in an area impacting the elements-at-risk; V is the physical vulnerability, specified as the degree of damage to a specific element-at-risk Es given the local intensity caused due to the occurrence of hazard scenario Hs A is the quantification (value) of the specific type of element at risk evaluated. If the value is expressed in monetary terms, the risk may also be expressed as potential damage.

  13. Private Losses Public Losses Private Losses Public Losses Types of risk Risk is the product of probability and expected losses. RISK Indirect losses Direct losses Tangible losses Intangible losses Tangible losses Intangible losses

  14. Risk definition Risk = Hazard * Vulnerability * Amount of EaR

  15. Most simple: risk = exposure Useful first approach Also a step in advanced risk assessment Spatial overlay of: • a hazard footprint of a particular event; • and elements at risk. Gives the number of elements at risk affected. Vulnerability is not used in this simple context.

  16. Landslide risk

  17. Problems

  18. P(DB |SVT ) P(RX |SVT) P(SPV | TM) P(SQT| TM) Specific risk for a house being flooded Rf = P(SQT| TM)xP(SPV | TM)xP(RX |SVT)xP(DB |SVT )xCB In which: P(SQT| TM) = Temporal probability. Conditional probability of the occurrence of a flood with a specific volume within a certain time period. P(SPV | TM) = Spatial probability. Conditional probability of initiating a flood with a specific volume at a specific location, given a certain triggering event (dike breach, overbank flow) with a certain magnitude. P(RX |SVT) = Conditional probability of the flood extent given the river discharge and the breach or overbank flow conditions. P(DB |SVT ) = Conditional probability of damage to the house, given the occurrence of the flood and given the spatial/temporal characteristics of the flood. CB = replacement costs of the particular building.

  19. Risk Assessment Risk assessment should be: • Multi-hazard • Multi-sectoral • Multi-level • Multi-stakeholder • Multi-phase

  20. Generation of the Risk Curve

  21. Landslide risk Task : Calculation of a risk curve Calculate the specific risks for the individual risk scenarios for 50, 100 and 200 years, using the temporal probability (PT), the amount (A), and the vulnerability (V). In this case make an estimate of the expected degree of loss given the particular scenario. Calculate the consequences (V*A) and the sum of the consequences (∑V*A). Plot the Temporal probability against the total consequences and create the risk curve.

  22. Landslide risk Task : Calculation of a risk curve Calculate the specific risks for the individual risk scenarios for 50, 100 and 200 years, using the temporal probability (PT), the amount (A), and the vulnerability (V). In this case make an estimate of the expected degree of loss given the particular scenario. Calculate the consequences (V*A) and the sum of the consequences (∑V*A). Plot the Temporal probability against the total consequences and create the risk curve.

  23. Earthquake risk assessment Fill in the joint frequency table Determine vulnerability for 3 types and MMIs

  24. Earthquake risk

  25. Earthquake risk

  26. Risk assessment • Overview of entire process for flooding & landslides • Individual GIS operations for each step • Resulting in risk curves ISL 2004

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