Michael K Deering, P.E ., D.WRE Senior Hydraulic Engineer Hydrologic Engineering Center, CEIWR-HEC

1. Flood Risk and Asset Management using HEC-WAT with FRA Compute Option Michael K Deering, P.E., D.WRE Senior Hydraulic Engineer Hydrologic Engineering Center, CEIWR-HEC International Workshop to Discuss the Science of Asset Management 9 December 2011

2. Flood Risk Management with HEC-WAT with FRA Compute Option • Systems Approaches and USACE Guidance • Introduction to the HEC-WAT • Introduction to HEC-WAT with FRA compute option • Economic and Performance Metrics • Columbia River Treaty HEC-WAT/FRA Application

3. Need for System Approaches with Risk Analysis • ER 1105-2-100, Planning Guidance Notebook, 22 April 2000, requires systems approaches, "The planning process shall address the Nation’s water resources needs in a systems context…" • ER 1105-2-101, Risk Analysis for Flood Damage Reduction Studies, 3 January 2006, requires risk analysis for all flood damage reduction studies, "All flood damage reduction studies will adopt risk analysis…“ • EC 1105-2-409, Planning in a Collaborative Environment, 31 May 2005, provides revised procedures for conducting Corps water resources planning, "Collaboration is the keystone of the Corps watershed approach…" • USACE Campaign Plan, Goals 1 - 4, require comprehensive systems approaches that include integrated sustainable solutions where decisions are risk-informed

4. Watershed Analysis Tool (HEC-WAT) An overarching interface that allows the PDT to perform water resources studies in a comprehensive, systems based approach by building, editing and running models commonly applied by multi-disciplinary teams and save and display data and results in a coordinated fashion.

5. Environmental Hydrology Flood Damage Reservoir Hydraulics

7. Interactive Schematic Computation Editors Output Displays

8. HEC-WAT Model Integration • Integrate model and tools used during the analytical process • Hydrology - HEC-HMS, GeoHMS • Reservoir Operations - HEC-ResSim • Hydraulics - HEC-RAS, GeoRAS • Economics - HEC-FIA • Environmental - HEC-EFM • Statistical - HEC-SSP • Other software - GSSHA, FLO-2D, ADH, RiverWare • Share data across models • Involve modelers early in the study process; encourages a team approach

9. Development of FRA Compute Option • CEIWR-HEC began researching and creating a tool within the WAT that would perform risk management with parameter sampling and a life-cycle approach. • Provides a systems and life-cycle approach to plan formulation for assessing risks and uncertainties in simple systems as well as complex, interdependent systems. • Provides an effective tool for risk communication. • FRA will apply the Monte Carlo simulation & allow for a life-cycle type computation of consequences (economic and loss-of-life) and associated performance indices. • Incorporate new computational methodologies.

11. FRA Monte Carlo Sampling Sequence For each project alternative, a single scenario of the project life cycle (e.g., 50 years) is simulated by sampling annual maximum flood events for the duration of the life cycle. For agricultural damage, may sample season by season within each year, or sample a time of occurrence. Hydrologic Sampling Sample Historic Pool of events with associated Hydrograph Set or Sample from frequency curve and hydrograph sets Sample System-Wide Fragility Functions

12. FRM Monte Carlo Sampling Sequence(Continued) Route Hydrograph Set Consequence Area (CA) system Failures are based on hydraulics and fragility curves Hydrographs will get adjusted as Dictated by Spills/Failures based on hydraulic model Determine Flow and Stage at all Consequence Areas 2D Spreading can be performed in areas where needed Compute Damage/Loss-of-Life for all Consequence Areas Repeat

13. FRM Sampling SequenceComputing EAD by Event Sampling Simple Monte Carlo Simulation Reservoir Analysis Channel Hydraulics Levee Behavior Hydrograph sets Peak Discharge (cfs) Exceedance Probability Random choice of probability U[0,1] to "generate" event Method 1 stage One Realization Spreading Model Inundation Mapping Structure Inventory Damage to Structures damage Damage(i) After all realizations are computed you now have EAD:

14. Hydrologic Sampling - Method 2 • pull out an event, use all its hydrographs, put it back…SHAKE • pull out an event, use all its hydrographs, put it back…SHAKE • pull out an event, use all its hydrographs, put it back…SHAKE keep events whole 100-year 1 20 8 14 12 4 200-year 22 10 19 17 6 500-year 18 2 16 3 21 7 5 9 13 11 15

15. 20-years of 50-year life-cycle after drawing 50 random U[0,1] values 200-year event

16. Qi Qb Inflow Qi Inflow Qi Inflow Qi Time Time Time Reservoir 1 Li Reservoir 2 Qo Outflow Qo Stage (ft) Time Probability of Levee Failure FRM Load Distribution

17. Inflow Qi Inflow Qi Inflow Qi Time Time Time Li Stage (ft) Cn+1 Probability of Levee Failure Cn Inflow Spreading and Consequences

18. Consequence Analysis - Inundation Mapping on Structure Inventory

19. Risk Communication • Life-Cycle Economic Performance • Annual Exceedance Probability • Conditional Non-Exceedance Probability • Long-Term Exceedance Probability • Loss-of-Life • Risk Maps

20. EACn+1 - EACn < Tol ? EAC1 = Ctot/ 500 EAC2 =Ctot/ 2*500 EACn= Ctot/ n*500 EACn+2 = Ctot/ (n+2)*500 N Y EADw/o- EADw = DR BNet = DR - EAC Y EADn+2 = Dtot/ (n+2)*500 EADn+1 - EADn < Tol ? EAD1 = Dtot/ 500 EAD2 = Dtot/ 2*500 EADn= Dtot/ n*500 N

21. Life-Cycle Transients in HEC-FRM • Watershed Variables (HMS, RAS) • Operational Variances (ResSim, RAS) • Diminished structure values after event (FIA) • Increasing Structure values during rebuild (FIA) • Diminishing levee/component fragility over time (RAS) • Increased stability after O&M, repair, or rehabilitation (RAS)

22. Net Benefits with Uncertainty • EADw/o- EADw = DR (DR=Damages Reduced) • BNet = DR – EAC (EAC=Expected Annual Cost) • Determine BNet probability distribution by sampling DR and EAC distributions

23. Annual Exceedance Probability - AEP • Key element in defining the performance of a plan. It is the probability that a specific capacity or target stage will be exceeded in a given year. For levees, the chance of failure or exceedance in any given year. • HEC-WAT calculates AEP at every grid cell and structure • AEP in this instance is probability of ground stage being equaled or exceeded • Creating a flood map from this data will be a simple raster calculation within a GIS program

24. CNP or Assurance 100 25 20 90 15 80 10 5 • The index that a specific target (e.g. the top of a levee) will not be exceeded, given the occurrence of a specific flood event. 70 60 3.63 50 40 30 87% of AEPs for 70' are less than 1% 20 10 0 83 76 87% of 1% stages are less than 70' 0 70 1.81 2.07 2.33 2.59 2.85 3.11 3.37 64 58 52 46 99 90 75 50 25 10 5 2 1 .5 .2 .1 0 10 20

25. Long Term Exceedance Probability • The probability that one or more flood events will occur within a specified time period or the likelihood the target stage will be exceeded in a specified time period. The calculations are made directly using the binomial distribution (see EM 1110-2-1415). • Long-Term Exceedance Probability = 1 – (1-AEP)n • AEP = annual exceedance probability • n = term of interest (e.g., thirty years)

26. Loss of Life • HEC-FIA can do Life Loss estimation. Care needs to be taken to make parameters match real life data (warning systems, population characteristics, flood evacuation plans)

27. HEC-WAT ApplicationColumbia River Treaty Study • From HEC-WAT the FRM compute option will be used to calculate the expected annual damage for the assumed post-2024 base condition. • The models that are part of HEC-WAT watershed are being developed with the flexibility to evaluate numerous hydrologic scenarios, including climate change, and numerous operational modifications during any time period.

28. FRM AEP Grid

29. Conclusion • USACE will conduct risk assessments in a systems context • HEC-WAT/FRM will be a tool that performs these calculations • It will include systems approaches, event sampling, alternative analyses, structural and non-structural analyses, parameter sampling, life-cycle cost and economic analysis, loss-of-life, agricultural damage analyses. • Could be used nationwide for levee evaluations, levee assessments, and planning and design studies.

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