1. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Risk modeling

2. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions

3. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions

4. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Principles What is probabilistic risk analysis (PRA)? – Structured approach to identifying failure modes and analyzing their effects – Accounting scheme for combining uncertainties – Approach to reasoning about uncertainties using the math of probability. What it is not … –Inherently different from traditional practice

5. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Hazard Inventory Vulnerability Loss Risk models Some of the hazards (perils) modeled: –Earthquakes –Floods –Hurricanes –Fire, wildfire, conflagration –Tornados –Tsunamis –Landslides –Extreme weather

6. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Annual exceedance probability (AEP) Loss Exceedance Probability L p AEP = Annual probability of an event or consequence greater than a given level.

7. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions History The reason we use PRA is because we don’t have enough data.

8. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions History The reason we use PRA is because we don’t have enough data. The reason we use PRA is because people have (very) poor intuition about probability.

9. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Approaches to hazard modeling 1.Where most of the work is done for CAT models –Seismic –Hurricane –Flood –Fire 2.Approach I.Spatial statistical model of occurrence II.Historical frequency model of severity III.Spatial model of effect at a particular site (Note: there may by a difference between frequency of event and frequency of effect) Hazard Inventory Vulnerability Loss

10. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Earthquake risk Source: Jones, K. 2003 Willis Limited

11. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Wind risk the USAID Office of Foreign Disaster Assistance and the Caribbean Regional Program

12. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Wildfire outbreak risk Virginia Department of Forestry

13. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Approaches to inventory modeling Geospatial databases (GIS) Biggest advance in recent years; changing quickly Mostly publicly available records (e.g., HAZUS) –Impacted by DHS concerns Many web-based (free or cheap) tools Hazard Inventory Vulnerability Loss

14. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Approaches to vulnerability (reliability) modeling Failure modes and effects analysis (FMEA) Event tree analysis Fault tree analysis Stochastic simulation (Monte Carlo) Hazard Inventory Vulnerability Loss

15. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Principles Levels of probabilistic reasoning

16. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions FMEA Failure Modes and Effects Analysis

17. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions FMEA

18. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions FMEA

19. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions FMEA

20. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Event trees Simple representation of earth dam system

21. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Dam Safety Reasons for Dam Failures –OVERTOPPING ~ 35% of all failures Inadequate Spillway Design Debris Blockage of Spillway Settlement of Dam Crest –FOUNDATION DEFECTS ~ 30% of all failures Differential Settlement Sliding and Slope Instability High Uplift Pressures Uncontrolled Foundation Seepage

22. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Dam Safety Reason for Dam Failures –PIPING AND SEEPAGE ~ 20% of all failures Internal Erosion Through Dam Caused by Seepage- "Piping" Seepage and Erosion Along Hydraulic Structures Such as Outlet Conduits or Spillways, or Leakage Through Animal Burrows Cracks in Dam –CONDUITS AND VALVES ~ 10% of all failures Piping of Embankment Material Into Conduit Through Joints or Cracks –OTHER ~ 5% of all failures

23. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Event trees Generic event tree (US NRC 1975).

24. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Event trees Simple event tree for an embankment dam

25. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Event Trees Dependence of Probabilities on earlier events

26. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Event trees Annualized initiating event generates input

27. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Event Trees Event trees = sample space

28. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Event Trees

29. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Event Trees

30. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Event Trees Hydrologic, piping, and strength failure parts of the levee failure event trees

31. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Influence diagrams

32. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Event Trees Influence diagram for levee failure

33. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Event Trees Influence diagram for levee failure, including active decision node

34. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Event Trees Partial event tree for hydrologic failure at Alouette Dam (Salmon 1995)

35. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Dam Safety Different approaches of the various owners and regulators –Bureau of Reclamation –US Army Corps of Engineers –New South Wales (Austl) –Canadian Electricity Association Dam Safety Interest Group – BCHydro, OPG, HydroQuebec, Vattenfall, Scottish & Southern Energy Ontario Ministry of Natural Resources & OPG –Department of Environment and Rural Affairs (DEFRA- UK)

36. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Glenmaggie Dam

37. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Fault tree analysis

38. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Fault tree analysis

39. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Fault trees Fault tree of dam failure (Fry 2001)

40. “ Building Strong “ Delivering Integrated, Sustainable, Water Resources Solutions Approaches to consequence modeling Economics (NED) Loss of life/property Environmental Historical Hazard Inventory Vulnerability Loss