Contents. Specific and total risk. Definition of risk. How to express risk? Multi-hazard Risk Assessment. Risk types

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1 Contents Multi-hazard Risk Assessment Cees van Westen United Nations University ITC School for Disaster Geo- Information Management International Institute for Geo-Information Science and Earth Observation (ITC) Enschede, The Netherlands Multi-hazard risk assessment Some schematic examples RiskCity case study Landslide risk assessment Flood risk assessment Spatial Multi-Criteria Analysis Annual loss estimation Conclusions Definition of risk The term risk refers to the expected losses from a given hazard to a given element at risk, over a specified future time period. According to the way in which the element at risk is defined, the risk may be measured in terms of expected economic loss, or in terms of numbers of lives lost or the extent of physical damage to property. (UNDRO, 1979) Specific and total risk Specific risk (Rs): the expected degree of loss due to a particular natural phenomenon. It may be expressed by the product of H, V and amount A. Rs = H * V * A Total risk (Rt): the expected number of lives lost, persons injured, damage to property, or disruption of economic activity due to a all natural phenomena. It is therefore the sum of the specific risks for all return periods and all types of events. SUM( Rs = H * V * A) For all elements at risk For all magnitudes For all landslide types Individual risk: the risk of fatality or injury to any identifiable (named) individual who live within the zone impacted by the landslide; or follows a particular pattern of life that might subject him or her to the consequences of the landslide. Risk types How to express risk? Suppose: What is the risk of flying by airplane? Is it higher than driving a car? Societal risk: the risk of multiple fatalities or injuries in society as a whole: one where society would have to carry the burden of a landslide causing a number of deaths, injury, financial, environmental, and other losses. F-N curves

2 How to calculate risk? RISK = HAZARD*VULNERABILITY*AMOUNT Example: Let us start simple US $ 5. RISK = Probability * Consequences 1 years RP V = 1 RISK = HAZARD * VULNERABILITY CAPACITY RISK = f(hazard, Vulnerability, Exposure) Hazard = probability within a given period =.1 / year Risk = hazard * vulnerability * amount =.1 * 1 *5. Simple example landslides Example: US $ 5. There are more elements at risk Example: US $ 2. US $ 5. US $ 1. V =.1 RP = 1 years 1 years RP V =.5 V = 1 V =.1 Hazard = probability within a given period =.1 / year Risk = hazard * vulnerability * amount =.1 *.1 *5. = 5 US $ Risk = hazard * vulnerability * amount =.1 * ( (.5*2.)+ (.1*1.)+ (1 * 5.)) =.1 * 16. = 16. $ There are more elements at risk US $ 1. US $ 5. US $ 2. V =.1 V = 1 Risk = H * V * A Different return periods US $ 5. P=.2 V = 1 P=.1 V =.1 P=.5 V =.1 V =.5 RP = 1 years Risk = hazard * vulnerability * amount =.1 * ((.1 *5.)+(.5*2.)+(1*1.)) = 5. * ((.5 *.1 ) + (.1 *.1) + (.2 * 1) + many more.. Probability (annual) Risk curve 1 Consequences 1 Probability (annual) Total risk = are under the curve 1 1 Consequences

3 Now it is getting complicated P=.5 V=.5 V = 1 P=.1 P=.2 V =.1 P=.5 V =.1 P=.2 V=1 US $ 5. P=.2 P=.1 OK, but how to know all this? RISK = HAZARD * VULNERABILITY * AMOUNT RISK = P * V * A P= high P= moderate P= low V=? P=? V=? V =? V =? V =? A = US $ 5. P=? P=? P=? = 5. * ((.5 *.1 ) + (.1 *.1) + (.2 * 1) + ((.5 *.5 ) + (.1 *.2) + (.2 * 1) + Probability (annual) Risk curve 1 Consequences 1 Direct losses Indirect losses Types of losses Human - social Physical Economic Fatalities Injuries Loss of income or employment Homelessness Diseases Permanent disability Psychological impact Loss of social cohesion due to disruption of community Political unrest Structural damage or collapse to Structural damage infrastructure Non-structural damage and damage to contents Progressive deterioration of damaged and infrastructure which are not repaired Interruption of business due to damage to and infrastructure Loss of productive workforce through fatalities, injuries and relief efforts Capital costs of response and relief Economic losses due to short term disruption of activities Long term economic losses insurance losses weakening the insurance market Less investments Capital costs of repair Reduction in tourisms Cultural Environmental Sedimentation Pollution Endangered species Destruction of ecological zones Destruction of cultural heritage Loss of biodiversity Loss of cultural diversity N Guantánamo Province 1181 m m San Antonio del Sur Mun. 1:5, 27,59 hab 6 km² Multi-scale approach 1:1, 6,17 km² 59,65 hab Cuban Archipelago 11,86 km² Sierra de Caujerí scarp 753 m 178 m Jagüeyes landslide 147 hab 1.5 km 1:1,, 11,217,1 hab 1974 m m 7686 m 1:25, 1489 hab 1:1, 1.5 km² 69 m 2 m 157 m m 75 km² N RiskCity training package Open source software Steep learning curve Continued learning Free access to training materials Contents: Hazard assessment Elements at risk Vulnerability Risk assessment Risk reduction planning High res image Ward & census DEM Lidar Flowchart Thematic layers: Flood discharges Seismic catalogs Soil and rock data Landslide information Technological information etc. Elements at risk Hazard maps Building Attributes: Landslides Flooding Technological Earthquake Urban land use Nr of Height of Risk = Hazard * Vulnerability * Amount Nr. people (daytime) Nr. people (nighttime) Risk maps Risk curve Landslides Flooding Technological Earthquake

4 Location and study area Background & introduction Rio Grande Choluteca Rio Chiquito Flow chart of the procedure Spatial Multi-Criteria Evaluation RISK = HAZARD * VULNERABILITY CAPACITY Indicators 1. Generic social vulnerability indicators: Percentage of young children Percentage of elderly people Percentage of minority groups Percentage of single parent households Percentage of households living below poverty level. Literacy rate 2. Hazard specific social vulnerability indicators people located in flood risk zones, both a daytime and nighttime scenario people located in landslide risk zones, both a daytime and nighttime scenario people located in technological risk zones, both a daytime and nighttime scenario people located in seismic risk zones, both a daytime and nighttime scenario 3. Hazard specific physical vulnerability indicators located in flood risk zones, with different return periods located in landslide risk zones, with different degree of susceptibility to landslides located in technological risk zones, with different degree of susceptibility to landslides located in seismic risk zones, with different intensities and return periods 4. Capacity indicators Distance to Evacuation sites Distance to hospitals. Awareness Different levels of aggregation Districts Wards Census tracts Mapping units City blocks Basic units for risk Building footprints Unemployment Literacy rate

5 SMCE process Identification of the main goal. Identification of a hierarchy of sub goals. Identification of criteria or effects, which measure the performance of the sub goals. Creating and filling a criteria tree, which represents the hierarchy of the main goal, any sub goals, and the criteria. Identification of alternatives to be evaluated. Assignment of input maps to criteria for each alternative. Determination of a standardization method per criterion. Weighing of criteria in the criteria tree. Calculation of the Composite Index maps and visualization. Classifying or slicing the Composite Index maps and visualization. Calculation of Shape Index and/or Connectivity Index. Spatial multi-criteria analysis A criteria tree contains all criteria Factors: a criterion that contributes to a certain degree to the output Benefits contributes positively to the output; the more you have (the higher the values), the better it is Costs contributes negatively to the output; the less you have (the lower the values), the better it is Constraints: criterion that determines in the calculation of the main goal.mask out area Criteria tree: Generic Social Vulnerability Generate Criteria Tree: Factors: Age related, Income Related, Ethnicity related, Social structure Link with attributes in tables Standardization Weighting Optional: constraint Standardization of criteria Maximum: The input values are divided by the maximum value of the map Interval: Linear function with the maximum and minimum values of the map Goal: Linear function with a specified maximum and minimum values Piecewise linear: Linear function with two breaking points located between the extremes Convex: Convex function with one user defined value to re-shape the curve Concave: Concave function with one user defined value to re-shape the curve U-Shape: U-shape curve with one user defined value to stretch or shrink the curvegaussianbell-shape curve with one user defined value to stretch or shrink the curve How to select weights? Direct estimation by expert The user has to specify weight values him/herself. These userdefined weights are automatically normalized Pair-wise comparison With a pairwise comparison matrix, each variable (or criterion) is compared to all others in pairs in order to evaluate whether they are equally significant, or whether one of them is somewhat more significant / better than the other for the goal concerned Ranking method the criteria and variables are simply ranked according to their importance as landslide controlling factors Source: ILWIS Multi Criteria Evaluation Criteria tree

6 Criteria tree: Physical Vulnerability & capacity Final combination The overall vulnerability indicator is made by combining the four indicator that we have calculated thus far: A. Generic_Social_Vulnerability (exercise 8.1) B. Population_Vulnerability (exercise 8.2) C. Physical_Vulnerability (exercise 8.3) Capacity (exercise 8.4) Combine A,B,C with SMCE Final Vulnerability := Vulnerability / Capacity 16% 9% 42% 33% No vulnerability Moderate Vulnerability Low Vulnerability High Vulnerability Quantitative Multi-Hazard Risk Assessment Procedure Normalize all specific risk scenarios: RISK = HAZARD * VULNERABILITY * AMOUNT Calculate annual risk Annual probability( for some we have to assume) Vulnerability (for some we have to assume) Amount (that is what we calculated already) Step 1: Defining earthquake scenario. Step 2: Calculate the attenuation Step 3: Calculate soil amplification Step 4: Convert PGA to MMI Step 5: Apply Vulnerability Functions for Building types Step 6: Apply Vulnerability Functions for Infrastructure types Step 7: Apply Vulnerability Functions for casualties If additional information is available: Step 8: Apply cost information to the and combine with vulnerability to calculate losses for different return periods. Step 9: Combine loss information for different return periods and calculate the risk by adding up the losses from these periods. Step 1: Combine information and make summary Seismic risk Seismic risk Risk = Hazard * Vulnerability * Amount Return period Probability Loss Risk Flood hazard modeling Sobek: a two dimensional hydraulic model. Input: Digital Surface Model (Lidar) Discharge data Roughness data (landuse) Output: Flood depth Flow velocity (Per time step) Series Discharge Time

7 5 years 5 years Flood risk 5 years 5 years Flood risk Risk = Hazard * Vulnerability * Amount 1 years 1 years 1 years 1 years 25 years Mapping units 25 years Hazard polygons Buildings Affected Flood risk Risk = Hazard * Vulnerability * Amount Qualitative risk assessment Qualitative_risk = Qualitative_risk [Susceptibility,Vulnerability] Return period Probability Susceptibility Loss Two dimensional table Risk Vulnerability Series Calculating in hazard zones Building map Cross Susceptibility Calculates the number of houses in High, Moderate and Low susceptibility zones using a Building footprint map Quantitative risk assessment Only susceptibility Still to do Risk = Hazard * Vulnerability * Amount How much percentage of the high, moderate and low hazard classes may be affected by landsides? In which period will these landslides occur? What is the vulnerability to landslides? Known now Results using mapping units High Moderate Low Hazard = Spatial probability * Temporal probability The temporal probability that landslides may occur due to a triggering event. Here we will link the return period of the triggering event with the landslides that are caused by it. We have differentiated return periods of: 5, 1, 2, 3 and 4 years. The spatial probability that a particular area would be affected by landslides of the given temporal probability. This is calculated as the landslide density within the landslide susceptibility class.

8 From susceptibility to hazard Landslide_ID map If the indication of the high, moderate and low areas susceptibility is correct, different landslide events with different return periods will give Million dollar different distributions of landslides in these information!!! classes. The probability can be estimated by multiplying the temporal probability (1/return/period for annual probability) with the spatial probability (= what is the chance that 1 pixel is affected) Calculating hazard Assumption is that events with a larger return period will also trigger those landslides that would be triggered by events from smaller return periods Return periods Landslide related to different return periods Susceptibility Cross Susceptibility classes Density in Density in high moderate Density in low Calculating Vulnerability Calculate losses Estimating landslide vulnerability is very complex. It requites knowledge on the building types and on the expected landslide volumes and velocities. These are difficult to estimate. In many study landslide vulnerability of is simply taken as 1, assuming complete destruction of the elements at risk. This would, however, in our case give too exaggerated values of risk. Simple assumption: The more there are with 3 floors or higher, the lower will be the landslide vulnerability, as it becomes less likely that large will be destroyed by landslides. Losses = Spatial Probability * Consequences Losses = Spatial P * V * A Loss_5_high:=.181*vuln*nr_b_high Loss_5_moderate:= E-6*vuln*nr_b_moderate Loss_5_low:= E-7*vuln*nr_b_low etc Vuln:=iff(PerVacant=1,,1-(Perc3floor+Percover3floor)) Calculate losses Losses for a return period = sum of losses in high, moderate and low susceptibility areas Period Calculate risk What can you conclude when you compare the spatial probabilities and consequences for the high, moderate and low susceptibility classes?

9 Series1.2.2 Materials provided for the Mountain-Risk Workshop Calculate total risk Total Risk = Area under curve Two methods: 1: Add trendline and integrate trendline 2: Use graphical method with triangles and rectangles Technological risk Risk = Hazard * Vulnerability * Amount Hazard class sc1 sc2 Buildings Return period 5 5 Probability.2.2 Vulnerability.1.1 Loss Risk 2 2 Combine hazard types Combine annual risk Convert to monetary values Calculate the total floorspace within each mapping unit. We do this by multiplying the building footprint area with the number of floors. Then we use unit costs (per square meter) per urban landuse type for and for contents of. Floorspace * unit costs = total costs per mapping units. Seismic & flooding Use the results from the annual loss estimation to combine these with the costs values. We will then combine the data and generate risk curves.

10 Landslides & Technological Combined Risk reduction Thank you