US Army Corps of EngineersBUILDING STRONG®
USACE Levee Safety Risk AnalysisProcess and Methodology Overview
Jason Needham, P.E.Consequence Specialist
USACE Risk Management Center
09 December 2011
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Levees pose risk to people and property► Inherent risk associated with living near rivers and oceans► Degradation of existing structures► Changing construction techniques► Increase in population, climate change, etc
Increase in public awareness► Katrina and other recent events► Congress points to USACE
Large portfolio - limited funds► How do you decide what to fix first?
Problem
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Previous Situation
HQ
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Assess the integrity and viability of levees and recommend actions to assure they do not present unacceptable risks to the public, property, and the environment.
► Hold public safety paramount► Reduce economic damage► Maximize cost effectiveness► Develop reliable and accurate
information (decision driven)► Build and maintain public trust
USACE Levee Safety Program
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Levee Safety Portfolio Risk Management
Process
5
RoutineInspections
Incident or inspection
finding triggers LSAC
review?
NO
IRRM
Levee issue requires further
evaluation?
No
Implement Risk Management
Measures
Yes
Reassess Risk & Revise LSAC
YES
All Levees
PeriodicInspections
Classification(LSAC)Screening
No Routine O&M& Monitoring
Yes
Study Justified?
Base Condition Risk Assessment
LSAC Communicationand
Plan Non-routine ActivitiesLevee Safety Risk Management Study
(Major Rehab/Feasibility)
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Levee Safety Portfolio Risk Management
Process
Routine Activities
6
RoutineInspections
Incident or inspection
finding triggers LSAC
review?
NO
IRRM
Levee issue requires further
evaluation?
No
Implement Risk Management
Measures
Yes
Reassess Risk & Revise LSAC
YES
All Levees
PeriodicInspections
Classification(LSAC)Screening
No Routine O&M& Monitoring
Yes
Study Justified?
Base Condition Risk Assessment
LSAC Communicationand
Plan Non-routine ActivitiesLevee Safety Risk Management Study
(Major Rehab/Feasibility)
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Levee Safety Action Classification System
Transition from Routine to Non-routine Reflects urgency of action Depicts range of risk
►combination of • likelihood of inundation • consequences of inundation• with an emphasis on life-safety
Provides consistent and systematic guidelines for actions commensurate with the risk
7
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Levee Safety Action Classification
Class Urgency Characteristics Actions
I Urgent and Compelling(Unsafe)
Likelihood of inundation with
associated consequences
characterizing each class.
Actions recommended for each class and level of
urgency.
II Urgent(Unsafe or Potentially Unsafe)
III High Priority(Potentially Unsafe)
IV Priority(Marginally Safe)
V Normal(Adequately Safe)
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Levee Safety Portfolio Risk Management
Process
Non-Routine Activities
9
RoutineInspections
Incident or inspection
finding triggers LSAC
review?
NO
IRRM
Levee issue requires further
evaluation?
No
Implement Risk Management
Measures
Yes
Reassess Risk & Revise LSAC
YES
All Levees
PeriodicInspections
Classification(LSAC)Screening
No Routine O&M& Monitoring
Yes
Study Justified?
Base Condition Risk Assessment
LSAC Communicationand
Plan Non-routine ActivitiesLevee Safety Risk Management Study
(Major Rehab/Feasibility)
BUILDING STRONG®10
RoutineInspections
Incident or inspection
finding triggers LSAC
review?
NO
IRRM
Levee issue requires further
evaluation?
No
Implement Risk Management
Measures
Yes
Reassess Risk & Revise LSAC
YES
All Levees
PeriodicInspections
Classification(LSAC)Screening
No Routine O&M& Monitoring
Yes
Study Justified?
Base Condition Risk Assessment
LSAC Communicationand
Plan Non-routine ActivitiesLevee Safety Risk Management Study
(Major Rehab/Feasibility)
Levee Screening Tool► Developed to quickly assess
the condition and consequences of levees in the Corps of Engineers portfolio
► Combines information from:• National Levee Database;• Levee inspection process;• Limited Engineering
Assessment of project features.
► Relative Risk Index► Philosophy
• Data consistency• Conservative judgements
► Largo portfolio• Simplify!
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Plotting – Prior to Overtopping
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Initial Results – New Orleans
System levees designed to reduce flooding from Mississippi River and Lake Pontchartrain
FOR OFFICIAL USE ONLY
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Segment Screenings
Vicinity/Segment Map
Pontchartrain LD
East Jefferson LD Orleans LD
2
1
3
5
46
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Plotting – Overtopping
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Initial Results – New Orleans► Recommended LSAC Rating = LSAC 2► Combination of life, economic, or environmental consequences
with the probability of inundation due to overtopping with subsequent breach, is very high.
► Justification:• Performance concern: Breach during overtopping• Evidence:
Good performance expected for events up to 100% loading Incipient overtopping frequency estimated at 200-year return period Studies show breach likely for event at or about 200-500 yr event Breach during overtopping would significantly increase consequences Critical infrastructure includes numerous hospitals, oil & gas refineries, and
chemical industry facilities that could lead to major impacts well beyond the protected area
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RoutineInspections
Incident or inspection
finding triggers LSAC
review?
NO
IRRM
Levee issue requires further
evaluation?
No
Implement Risk Management
Measures
Yes
Reassess Risk & Revise LSAC
YES
All Levees
PeriodicInspections
Classification(LSAC)Screening
No Routine O&M& Monitoring
Yes
Study Justified?
Base Condition Risk Assessment
LSAC Communicationand
Plan Non-routine ActivitiesLevee Safety Risk Management Study
(Major Rehab/Feasibility)
Levee Safety Portfolio Risk Management
Process
16
When We Use Risk Analysis
Risk Analysis Approach is
Decision Driven
Relative
Absolute
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USBR Public Protection Guidelines
1.E-08
1.E-07
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
1.E-01
1.E+00
0.1 1 10 100 1000 10000
Average Incremental Life Loss Per Failure
Ave
rage
Ann
ual P
roba
bilit
y of
Fai
lure
USBR Justification to take expedited action to reduce risk
USBR Justification to take action to reduce risk
USBR Justification to take action to reduce probability of failure
USBR Diminishing justification to take action to reduce risk
ANCOLD Tolerable Risk Guidelines
1.E-08
1.E-07
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
1.E-01
1.E+00
1 10 100 1000
Incremental Life Loss Due to Dam Failure (N)
Ann
ual P
roba
bilit
y of
Incr
emen
tal L
ife L
oss
>= N
ANCOLD Limit Of Tolerability For Existing Dams
ANCOLD Limit Of Tolerability For New Dams and Major Modifications