US Army Corps of Engineers

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Michael K Deering, P.E., D.WRESenior Hydraulic EngineerHydrologic Engineering Center, CEIWR-HEC

Flood Risk and Asset Management using HEC-WAT with FRA Compute Option

International Workshop to Discuss the Science of Asset Management

9 December 2011

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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

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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

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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.

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Reservoir

Environmental

Hydraulics

Hydrology

Flood Damage

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HEC-WAT Framework

HEC-WATSimulation

With DefaultProgram

Order

HEC-ResSim Plug-In

HEC-RAS Plug-In

HEC-HMS HEC-ResSim HEC-RAS HEC-FIA

HEC-HMS Plug-In

HEC-FIA Plug-In

Model Results (simulation.dss)

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Interactive Schematic

Output Displays

Computation

Editors

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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

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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.

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No

HEC-WAT Framework with FRM Compute Option & Cost Analysis

FrequencySamplerPlug-In

FragilitySamplerPlug-In

HEC-RASPlug-In

SpreadingPlug-In

HEC-FIAPlug-In

CostPlug-In

Spreading Model

CSRAFreq

SamplerFragilitySampler

HEC-RAS HEC-FIA

Model Results (simulation.dss)Hydrograph

SetsDamage

Sets

FrequencyInflow

HydrographSet

BreachHydrographs

Depths, Velocities per Grid

ExpectedNet Benefit,

CDF

NetBenefitSampler

BenefitsModel

Convergence?

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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

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FRM Monte Carlo Sampling Sequence(Continued)

●Route Hydrograph SetConsequence Area (CA) system Failures are based on hydraulics

and fragility curves Hydrographs will get adjusted as Dictated by Spills/Failures based

on hydraulic modelDetermine 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

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FRM Sampling SequenceComputing EAD by Event Sampling

SimpleMonte CarloSimulation

Random choice of probability U[0,1] to "generate" event Method 1

Reservoir AnalysisChannel HydraulicsLevee Behavior

After all realizations are computed you now have EAD:

N

i

iDamageN

EAD1

)(1

Spreading ModelInundation MappingStructure InventoryDamage to Structures

stage

damageDamage(i)

Hydrograph sets

One Realization

Exceedance Probability

Pea

k D

isch

arg

e (c

fs)

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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…SHAKE7

5

26

9

4

1 8

3

10

11

14

13

12

16

15

1918

17

20

21

200-year

100-year

500-year

22

keep events whole

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20-years of 50-year life-cycle

after drawing 50 random U[0,1] values

0

100000

200000

300000

400000

500000

600000

200-year event

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FRM Load DistributionIn

flow

Qi

Time

Inflow

Qi

TimeIn

flow

Qi

Time

LiSta

ge (

ft)

Probability of Levee Failure

Qi Qb

Qo

Ou

tflow

Qo

Time

Reservoir 1

Reservoir 2

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Inflow Spreading and ConsequencesIn

flow

Qi

Time

Inflow

Qi

TimeIn

flow

Qi

Time

Li

Sta

ge (

ft)

Probability of Levee Failure

Cn

Cn+1

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Consequence Analysis - Inundation Mapping on Structure Inventory

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Risk Communication

● Life-Cycle Economic Performance

● Annual Exceedance Probability

● Conditional Non-Exceedance Probability

● Long-Term Exceedance Probability

● Loss-of-Life

● Risk Maps

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Y

EAD1 = Dtot / 500 EAD2 = Dtot / 2*500EADn+2 = Dtot / (n+2)*500

EADn+1 - EADn < Tol ?EADn = Dtot / n*500

EAC1 = Ctot / 500 EAC2 =Ctot / 2*500 EACn+2 = Ctot / (n+2)*500EACn+1 - EACn < Tol ?EACn = Ctot / n*500

Y

N

N

EADw/o- EADw = DR

BNet = DR - EAC

Example Realization of Project Life-Cycle

2010 2060

6/18/2010Project First Cost

COSTS

FLOOD DAMAGES

8/7/2021Flood Event 1

9/17/2022Repair for Event 1

8/8/2011O&M each year

12/18/2053Repair for Event 4

1/17/2035Scheduled Rehab of Pump Station

5/18/2029Flood Event 2

2/1/2042Flood Event 3

3/1/2053Flood Event 4

9/17/2042Repair for Event 3

5/8/2030Repair for Event 2

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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)

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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. Netbenefit 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 375 300 75 74 0.83 19 72 120

Detention basin 325 275 50 96 0.70 -17 50 113

Relocation 355 250 105 63 0.97 62 100 145

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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

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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.

99 90 75 50 25 10 5 2 1 .5 .2 .10

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

0 10 2046

52

58

64

70

76

83

1.81 2.07 2.33 2.59 2.85 3.11 3.370

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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 probabilityn = term of interest (e.g., thirty years)

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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)

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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.

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FRM

AEP Grid

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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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US Army Corps of Engineers

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QUESTIONS?

www.hec.usace.army.mil