Consequence Assessment for Dam Failure Simulations

Consequence Assessment for Dam Failure Simulations

Kurt Buchanan, CFM

Economist

Mapping, Modeling, and Consequences Center

US Army Corps of Engineers

Huntington, WV

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

USACE Dam SafetyRisk Assessment Activities

Screening

Minimal effort, classify portfolio

Periodic Assessments and

Issue Evaluation Studies

Validate screening, identify path forwardDam Safety Modification Studies (DSMS)Risk reduction alternative analysisCritical 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

Increasing Risk

Consequence

Probability

RISK =

(Probability

, Consequence)

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

USACE Dam SafetyConsequence Assessment Workflow

New Risk Assessment

3 new “teams”

MMC (H&H/Econ)

Generic dam break modeling

Consequence modeling (HEC-FIA)

Risk Team (H&H/Econ)

PFMA specific dam break modeling

Consequence model refinement (HEC-FIA)

Dam Break & HEC-FIA models

District

Team

Dam break modeling input and “QC”

Consequence modeling input and “QC”

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

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 capabilityEvacuation velocityModeled as a straight line from the structure to the nearest safe zone, average evacuation speed is set at an average of 10 mphWarning time relative to the breach initiation

Consequence EstimationMobilization Curve Example

Consequence EstimationExample of a HEC-FIA Model

Consequence EstimationHow HEC-FIA WorksFor physical damages:

Determine

the inundation depth

at

the structure from the depth grid

Apply the appropriate depth-damage curves based on structure typeFor life loss estimate:Determine if population was warned and had time to mobilize from arrival time dataAssign a fatality rate for remaining population based on inundation depth and structure type

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'

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

Double-Warning ProcedureMust be implemented any time there is significant non-fail Population at Risk

13

TIME

Overtopping

Failure Expected

Failure

FLOW

Failure Evac.

Warning

Major

Flooding

Forecast

Major Flood Evac.

Warning

Damaging Release

HEC-FIA

WARNING

ISSUANCE

TIMES

Consequence Estimation

Example HEC-FIA Model

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

Consequence Estimation

Results

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

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…

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

Summary

Corps Dam Safety Program overview

Consequence Estimation Using HEC-FIA (Flood Impact Analysis)

Data inputs required

Methodology used by the software

ResultsIndentifying Critical Infrastructure within dam failure inundation areas

Questions?

My Contact Info:

Kurt Buchanan

Kurt.L.Buchanan@usace.army.mil

(304) 399-5187

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