1. International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 RiskCity Exercise: Quantitative annual multi hazard risk assessment using risk curves 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 E-mail: westen@itc.nl Associated Institute of the

2. International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Loss estimation methods Qualitative: Overlay of hazard footprints and elements at risk Using a simple matrix approach Using indicator analysis ( e.g. SMCE) Using risk indices Semi-Quantitative: Scenario-based loss estimation Probabilistic loss estimation R = H * V * A Quantitative (QRA) Based on economic losses Involving direct and indirect losses RISK = HAZARD * VULNERABILITY * AMOUNT

3. International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 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)

4. International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Seismic risk 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 buildings 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 10: Combine information and make summary

5. International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Seismic risk Return period15355060 Probability0.0670.0290.0200.017 Loss13234850894510991 Risk88139179183 Risk = Hazard * Vulnerability * Amount

6. International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 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) Discharge Time 5 10 25 100

7. International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Flood risk 5 years 10 years 25 years 50 years 100 years Mapping units 5 years 10 years 25 years 50 years 100 years Hazard polygonsBuildings Affected

8. International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Flood risk Risk = Hazard * Vulnerability * Amount

9. International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Flood risk Return period5102550100 Probability0.20.10.040.020.01 Loss33741924051096 Risk778811 Risk = Hazard * Vulnerability * Amount

10. International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Qualitative risk assessment Qualitative_risk = Qualitative_risk [Susceptibility,Vulnerability] Vulnerability Susceptibility Two dimensional table

11. International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Calculating buildings in hazard zones Calculates the number of houses in High, Moderate and Low susceptibility zones using a Building footprint map Building mapSusceptibility 4426 buildings 9645 buildings 22019 buildings Cross

12. International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Quantitative risk assessment 4426 buildings 9645 buildings 22019 buildings 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? Results using mapping units HighModerateLow Known nowStill to doOnly susceptibility 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: 50, 100, 200, 300 and 400 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.

13. International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 From susceptibility to hazard Million dollar information!!! Landslide related to different return periods 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 different distributions of landslides in these 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) Susceptibility Cross Density in high Density in moderate Density in low

14. International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 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 Susceptibility classes Return periods

15. International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Calculating Vulnerability Simple assumption: The more buildings there are with 3 floors or higher, the lower will be the landslide vulnerability, as it becomes less likely that large buildings will be destroyed by landslides. Vuln:=iff(PerVacant=1,0,1-(Perc3floor+Percover3floor))  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 buildings 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.

16. International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Calculate losses Loss_50_high:=0.0181*vuln*nr_b_high Loss_50_moderate:= 1.31199E-06*vuln*nr_b_moderate Loss_50_low:= 5.96345E-07*vuln*nr_b_low etc Losses = Spatial Probability * Consequences Losses = Spatial P * V * A

17. International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Calculate losses What can you conclude when you compare the spatial probabilities and consequences for the high, moderate and low susceptibility classes ? Losses for a return period = sum of losses in high, moderate and low susceptibility areas

18. International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Calculate risk Period

19. International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Calculate total risk Total Risk = Area under curve Two methods: 1: Add trendline and integrate trendline 2: Use graphical method with triangles and rectangles

20. International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Technological risk Hazard classsc1sc2 Buildings82810843 Return period50500 Probability0.02000.0020 Vulnerability0.1 Loss82.81084 Risk22 Risk = Hazard * Vulnerability * Amount

21. International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Combine hazard types

22. International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Combine annual risk

23. International Institute for Geo-Information Science and Earth Observation (ITC) ISL 2004 Thank you