US Army Corps of Engineers

BUILDING STRONG®

Consequence Assessment for Dam Failure Simulations

Kurt Buchanan, CFMEconomistMapping, Modeling, and Consequences CenterUS Army Corps of EngineersHuntington, WV

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Overview

Corps Dam Safety Program overview

Consequence Estimation Using HEC-FIA (Flood Impact Analysis)

► Data inputs required► Methodology used by the software► Results

Indentifying Critical Infrastructure within dam failure inundation areas

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USACE Dam SafetyRisk Assessment Activities

Screening► Minimal effort, classify portfolio

Periodic Assessments andIssue Evaluation Studies

► Validate screening, identify path forward

Dam Safety Modification Studies (DSMS)

► Risk reduction alternative analysis

Critical Infrastructure Protection and Resiliency (CIPR)

► Aligned with DHS homeland security

High Probability

High Consequence

Low Probability

Low Consequence

High Probability

Low Consequence

Low Probability

High Consequence

Increasin

g Risk

Consequence

Pro

bab

ility

RISK = (Probability, Consequence)

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USACE Dam SafetyMapping, Modeling, and Consequences Team

Virtual team of technical experts from across the Corps GIS specialists, hydraulic engineers, and economists Provides a standard operating procedure, technical

training, and quality reviews Produces a dam break hydraulic model, consequence

estimate, and inundation map for each project Results in a quality standardized product to support the

risk assessment process

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USACE Dam SafetyConsequence Assessment Workflow

New Risk Assessment

3 new “teams”

MMC (H&H/Econ)1. Generic dam

break modeling2. Consequence

modeling (HEC-FIA)

Risk Team (H&H/Econ)1. PFMA specific dam

break modeling2. Consequence

model refinement (HEC-FIA)

Dam Break & HEC-FIA models

District Team 1. Dam break

modeling input and “QC”

2. Consequence modeling input and “QC”

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Consequence EstimationCorps HEC-FIA Software

GIS-based software program, currently beta version

Uses data from a HEC-RAS dam failure model (depth grids, hydrograph, cross sections, etc.)

Structure inventory can be developed using data from FEMA’s HAZUS program

► Tax parcel data or point shapefiles can also be used

Program gives a statistical estimate of direct damages and loss of life to individual structures

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Consequence EstimationHEC-FIA Variables

Warning System Curves► Default lowest curve is the emergency broadcast system

Mobilization curves► Default is a maximum of 98% of population mobilized► Can be changed depending on expected evacuation capability

Evacuation velocity► Modeled as a straight line from the structure to the nearest safe zone,

average evacuation speed is set at an average of 10 mph

Warning time relative to the breach initiation

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Consequence EstimationMobilization Curve Example

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Consequence EstimationExample of a HEC-FIA Model

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Consequence EstimationHow HEC-FIA Works

For physical damages:► Determine the inundation depth at the structure from

the depth grid► Apply the appropriate depth-damage curves based on

structure type

For life loss estimate:► Determine if population was warned and had time to

mobilize from arrival time data► Assign a fatality rate for remaining population based

on inundation depth and structure type

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Consequence EstimationFatality Rate Zones (1-story)

Fatality rates are based on historical averages

Chance Zone – 91% >FH + 15'

Compromized Zone - 12% FH + 13' to 15'

Safe Zone – 0.02%<FH + 13'

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Consequence EstimationDouble Warnings

Downstream inundation is split into two warning zones

► No Fail Zone – Area flooded prior to or regardless of the dam failure (i.e. spillway flow)• Population gets warned when flooding is predicted from

heavy rainfall and will have more time to evacuate

► Fail Zone – Not flooded until after the dam fails• Population is not at risk from normal flooding and will not

have any reason to evacuate until a dam failure occurs or is predicted to occur

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Double-Warning Procedure

Must be implemented any time there is significant non-fail Population at Risk

13

TIMEOvertopping

Failure ExpectedFailure

FLOWFailure Evac.

Warning

MajorFloodingForecast

Major Flood Evac.

Warning

Damaging Release

HEC-FIA WARNING ISSUANCE

TIMES

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Consequence EstimationExample HEC-FIA Model

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Consequence EstimationResults

Direct damage estimates to structures, contents, and vehicles

Population at risk during the day and at night

Loss of life during the day and at night

Agricultural damages

Results can be identified by locations/areas

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Consequence EstimationResults

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Critical InfrastructureWhy it matters

Important to identify Critical Infrastructure and Key Resources (CIKR) that could be at risk from a dam failure

Impacts caused by damage to CIKR are not included in the direct damage estimate

Impacts can be cascading

Potential damage to CIKR can be included in planning and mitigated for if identified

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Critical InfrastructureExamples of CIKR

Chemical manufacturing facilities, power generation plants, medical facilities

Water, sewer, and power infrastructure

Police stations, fire stations, prisons, schools

Transportation and communication networks

Many, many others…

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Critical InfrastructureCorps Path Forward

Currently developing a GIS-based method to identify and prioritize CIKR assets in inundation areas using DHS datasets

Priority will be given to CIKR that could impact human life safety

Integrate CIKR information into the overall risk estimate of each dam

Communicate risk levels to CIKR owners and operators

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Summary

Corps Dam Safety Program overview

Consequence Estimation Using HEC-FIA (Flood Impact Analysis)

► Data inputs required► Methodology used by the software► Results

Indentifying Critical Infrastructure within dam failure inundation areas

BUILDING STRONG®

Questions?

My Contact Info:► Kurt Buchanan► Kurt.L.Buchanan@usace.army.mil► (304) 399-5187

Hydraulic Engineering Center Website:► www.hec.usace.army.mil