International Workshop to Discuss the Science of Asset Management 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

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

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

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.

Hydrology Environmental Flood Damage Reservoir Hydraulics Configurations are defined globally and are available to all the CWMS standard models. 5

Interactive Schematic Output Displays Computation Editors

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

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. 9 9

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

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

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

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

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

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

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

Consequence Analysis - Inundation Mapping on Structure Inventory

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

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

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)

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 Plan Expected annual benefit and cost ($’000) Net benefits ($’000) Prob. Net benefit is>0 Net benefit that is exceeded with specified probability ($’000) Benefits Cost Mean Std. dev. 0.75 0.50 0.25 20’ levee 355 300 55 68 0.80 8 54 99 25’ levee 500 400 100 88 0.88 45 104 164 30’ levee 570 550 20 116 0.55 -62 14 91 Channel 375 75 74 0.83 19 72 120 Detention basin 325 275 50 96 0.70 -17 113 Relocation 250 105 63 0.97 62 145

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

CNP or Assurance 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. 10 20 30 40 50 60 70 80 90 100 87% of 1% stages are less than 70' 87% of AEPs for 70' are less than 1% 3.63 5 10 15 20 25 46 52 58 64 70 76 83 1.81 2.07 2.33 2.59 2.85 3.11 3.37 99 90 75 50 25 10 5 2 1 .5 .2 .1

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)

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)

HEC-WAT Application Columbia 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. 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. 27

FRM AEP Grid

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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