Report

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 US Army Corps of Engineers BUILDING STRONG® 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 BUILDING STRONG® 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 BUILDING STRONG® 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. BUILDING STRONG® Environmental Hydrology Flood Damage Reservoir Hydraulics BUILDING STRONG® HEC-WAT Framework HEC-HMS Plug-In HEC-ResSim Plug-In HEC-RAS Plug-In HEC-FIA Plug-In HEC-HMS HEC-ResSim HEC-RAS HEC-FIA HEC-WAT Simulation With Default Program Order Model Results (simulation.dss) BUILDING STRONG® Interactive Schematic Computation Editors Output Displays BUILDING STRONG® 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 BUILDING STRONG® 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 lifecycle type computation of consequences (economic and lossof-life) and associated performance indices. ● Incorporate new computational methodologies. BUILDING STRONG® HEC-WAT Framework with FRM Compute Option & Cost Analysis Frequency Sampler Plug-In Fragility Sampler Plug-In HEC-RAS Plug-In Spreading Plug-In HEC-FIA Plug-In Cost Plug-In Freq Sampler Fragility Sampler HEC-RAS Spreading Model HEC-FIA CSRA Frequency Breach Hydrographs Inflow Hydrograph Set Hydrograph Sets Depths, Velocities per Grid Model Results (simulation.dss) Net Benefit Sampler Damage Sets Model Convergence ? Expected Net Benefit, CDF Benefits No BUILDING STRONG® 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 BUILDING STRONG® 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 BUILDING STRONG® FRM Sampling Sequence Computing EAD by Event Sampling Hydrograph sets Peak Discharge (cfs) Reservoir Analysis Channel Hydraulics Levee Behavior Simple Monte Carlo Simulation Exceedance Probability stage Spreading Model Inundation Mapping Structure Inventory Damage to Structures Random choice of probability U[0,1] to "generate" event Method 1 One Realization damage Damage(i) After all realizations are computed you now have EAD: 1 N EAD Dam age(i) N i 1 BUILDING STRONG® Hydrologic Sampling - Method 2 ● pull out an event, use all its hydrographs, put it back…SHAKE keep events whole ● pull out an event, use all its hydrographs, put it back…SHAKE 100-year 1 200-year 500-year 8 12 22 6 7 15 18 5 20 14 4 10 21 13 19 2 16 9 17 3 ● pull out an event, use all its hydrographs, put it back…SHAKE 11 BUILDING STRONG® 20-years of 50-year life-cycle after drawing 50 random U[0,1] values 600000 500000 400000 200-year event 300000 200000 100000 0 BUILDING STRONG® Inflow Qi Inflow Qi FRM Load Distribution Time Time Qi Qb (ft) Reservoir 1 Stage Reservoir 2 Qo Outflow Qo Probability of Levee Failure Inflow Qi Li Time Time BUILDING STRONG® Inflow Qi Inflow Qi Inflow Spreading and Consequences Time Li Probability of Levee Failure Cn+1 Inflow Qi Stage (ft) Time Time Cn BUILDING STRONG® Consequence Analysis - Inundation Mapping on Structure Inventory BUILDING STRONG® Risk Communication ● Life-Cycle Economic Performance ● Annual Exceedance Probability ● Conditional NonExceedance Probability ● Long-Term Exceedance Probability ● Loss-of-Life ● Risk Maps BUILDING STRONG® EAC1 = Ctot / 500 EAC2 =Ctot / 2*500 EACn = Ctot / n*500 EACn+1 - EACn < Tol ? Example Realization of Project Life-Cycle COSTS 6/18/2010 Project First Cost 9/17/2022 Repair for Event 1 5/8/2030 Repair for Event 2 8/8/2011 O&M each year N EACn+2 = Ctot / (n+2)*500 Y 9/17/2042 Repair for Event 3 1/17/2035 Scheduled Rehab of Pump Station EADw/o- EADw = DR 12/18/2053 Repair for Event 4 BNet = DR - EAC 2010 2060 8/7/2021 Flood Event 1 5/18/2029 Flood Event 2 2/1/2042 Flood Event 3 3/1/2053 Flood Event 4 FLOOD DAMAGES Y N EAD1 = Dtot / 500 EAD2 = Dtot / 2*500 EADn = Dtot / n*500 EADn+1 - EADn < Tol ? EADn+2 = Dtot / (n+2)*500 BUILDING STRONG® 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) BUILDING STRONG® 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 Expected annual benefit and cost ($’000) Net benefits ($’000) Benefits Cost Mean Std. dev. Prob. Net benefit is>0 20’ levee 355 300 55 68 25’ levee 500 400 100 30’ levee 570 550 Channel 375 Detention basin Relocation Plan Net benefit that is exceeded with specified probability ($’000) 0.75 0.50 0.25 0.80 8 54 99 88 0.88 45 104 164 20 116 0.55 -62 14 91 300 75 74 0.83 19 72 120 325 275 50 96 0.70 -17 50 113 355 250 105 63 0.97 62 100 145 BUILDING STRONG® 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 BUILDING STRONG® 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. 100 90 25 20 80 15 70 87% of AEPs for 70' are less than 1% 60 10 83 5 0 76 70 1.81 2.07 2.33 2.59 2.85 3.11 3.37 3.63 64 58 50 52 46 40 0 30 10 20 87% of 1% stages are less than 70' 20 10 0 99 90 75 50 25 10 5 2 1 .5 .2 .1 BUILDING STRONG® 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) BUILDING STRONG® 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) BUILDING STRONG® 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 post2024 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. BUILDING STRONG® FRM AEP Grid BUILDING STRONG® 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. BUILDING STRONG® QUESTIONS? www.hec.usace.army.mil US Army Corps of Engineers BUILDING STRONG® BUILDING STRONG®