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© Arcadis 2015
USING RISK ANALYSIS TO INFORM LEVEE INVESTMENT PRIORITIES IN THE CA AND DUTCH DELTAS
Jessica Ludy, CFM
Larry Roth, PE
May 3, 2017
115 May 2017
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How lowlands 5,000 miles apart left the dark side for a risk-informed approach.
Jessica Ludy, CFM
Larry Roth, PE
May 3, 2017
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Dutch lesson
• Hoogwater
• Dijk
• Droge voeten
Dutch people are direct!
Dutch people love football.
Dutch people are very proud
Of their dikes.
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Problems: increasing risk
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We need a strategy to address it
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Evolution in thinking
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Flood control
“level of protection”
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Evolution in thinking
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Flood control
Recognition of unacceptable risks
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Evolution in thinking
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Flood control
Recognition of unacceptable risks
Flood risk management
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Today’s discussion
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Risk and tolerable risk guidelines
A tale of two deltas
How risk analysis was applied to inform strategy
RISK AND TOLERABLE RISK GUIDELINES
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What is risk ?
What are the
hazards and how
likely are they to
occur?
How will the
infrastructure
perform?
Who and what are in harms way?
USACE
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Risk = Probability x Consequences
Sacramento 1862
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How do we measure risk?
Loss of life: Expected Annual Fatalities (EAF)
• Considers the probability of flooding
• Number of individuals exposed to floodwaters
• Affected by warning time, water depth and velocity, rate of rise, water temperature, etc.
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How do we measure risk?
Damage to property and infrastructure: Expected Annual Damages (EAD)
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• Annual cost of flooding
• Integrates the product of:
the probability of flooding
potential economic damage over all flood levels
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Quantifying risk enables
How do we decide whether risks are tolerable?
• Understanding and communicating risk (and residual risk)
• Deciding if more risk reduction warranted
• Identifying actions to address most urgent risks
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What do we mean by tolerable?
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Consider that risk cannot be eliminated
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Tolerable risk is
Unacceptable Broadly acceptable
Range of Tolerability
The level of risk that people are willing to live with in order to secure certain benefits
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We make decisions everyday on what level of risk is tolerable to us
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Yet with floods, we rely on Levels of Protection
USACE
“100-yr level of protection”
44 Code of Federal Regulations
Measured with a water level.
Addresses only the hazard.What are the
hazards and how
likely are they to
occur?
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And we ignore the consequences
USACE
How will the
infrastructure
perform?
Who and what are in harms way?
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Using LOP ignores residual risk
Residual risk is the flood risk that remains after actions have been taken to reduce that risk
Adapted from Eisenstein et al (2007)
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Limitations of the LOP approach
• Implies risk can be eliminated
• Favors structural measures
• Focus on water level
• Basically an insurance standard
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The one-percent annual chance LOP is not a safety standard.
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Tolerable risk in other practices
Nuclear Power Plants Commercial Aviation
Dams Hazardous Occupations
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Tolerable Risk Guidance
Best practices identified by
USACE and USBR (2015)
USACE Design and
Construction of Levees
(2016) will encourage risk
assessment procedures
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Risk informed studies in the UK
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How to use risk analysis and TRG?
Identify Options to Reduce Risk Characterize Risk
Implement Options and
Continuously Review Risk Evaluate Options
1.
2.
3.
4.
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How safe is safe enough?
A policy decision with expert input
Informed by analysis and risk assessment
Considers:
• Individual risks
• Societal risks
• Equity
Use F-N plots to inform decisions
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A TALE OF TWO DELTAS
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California
Netherlands
Geography
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Image: Poolman-Schmidt
A tale of two Deltas
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A tale of two Deltas
Netherlands Delta California Delta
Miles of levees* 2,250 (primary) 1,100
Year reclaimed 1100 1850s
Land below sea level Yes (-9 feet-ish) Yes (-24 feet)
Population in Delta 9 million 500,000
Flood of record 1953 1862
(Katrina 2005)
Major concern Life safety, economic
development
Water supply reliability
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California Delta
Courtesy: Delta Stewardship Council3315 May 2017
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Mediterranean Marine
Climate and major rivers
Rhine River
766 mi
(starts in Switzerland)
400 mi
365 mi
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Deltas used to be wetlands:“Polderen”
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NetherlandsCalifornia
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Reclamation in Netherlands
Oldest dike 100-200 BCE
River embankments 1100
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Reclamation in California
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1850’s Westward movement and gold rush
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Levees &Management
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2,250 miles primary levees
26 “Waterschappen”
Oldest democratic inst. In EU
http://www.topomania.net/mapinfo/Wa
terschappen%20van%20Nederland
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Levees &Management
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1,100 miles primary levees
60 “islands” or polders
Over 100 Reclamation Districts
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Below sea-level
Ludy 2013
Hoekstra 2006
Public Policy Inst. California
Ranstad
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Below sea-level
Ludy 2013
Hoekstra 2006
Public Policy Inst. California
Sacramento
Stockton
Ranstad
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Dikes built for one purpose now serve many others
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Dikes built for one purpose now serve many others
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Levees critical for navigation
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Netherlands California
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Levees are critical for agriculture
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Netherlands California
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Similar hazards and consequences
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Floods
Earthquakes*
Subsidence
Seepage
Sea-level rise
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Water supply risk
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The Delta supplies water to
25 million people and
4 million acres farmland
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Flood of record-CA
1861-1862: “Inland Sea”
40 miles wide X 300 miles long
California: bankrupt
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Flood of record-NL1953
70,000 Evacuated
1,835 casualties
€450-680M damages
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How did these floods affect policy?
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Levee failures since flood of record?
Netherlands:
Levee failures = World Cup titles
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Levee failures since flood of record?
Netherlands:
Levee failures = world cup titles
California:
~ 200
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Unacceptable risk: Never Again!
The Delta Works (1958-1997)
Designed for Dry Feet, 2006
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Unacceptable risk: Never Again!
• Loosely risk-informed approach to setting safety standards
• But still largely “flood control”
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California: Ehh, it’d be nice if it didn’t flood again.
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CA DWR
But… Katrina
WHERE ARE WE NOWUsing Risk Analysis in the Deltas
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Recognition of unacceptable and increasing risks
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Delta Levees Investment Strategy
Charge: Recommend priorities for state investments in Delta levees to reduce flood risk
and advance the coequal goals.
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Environmental Science Associates
Catalyst Group
Convey
Shannon & Wilson
RiverSmith
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From Level of Protection to Risk
Scope of work: What is the appropriate level of protection (LOP) for each island?
What level of risk is tolerablekey stakeholders?
• Identify the hazards and consequences
• Quantify the risk
• Determine where risks are the greatest
• Determine the urgency for action
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Probability of flooding
Seismic Recurrence
Stage Recurrence
Levee Fragility
Inventory of flood hazards
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Consequences of flooding
Inventory of assets and people at risk:
Life
Property
• Homes and businesses
• Farms, livestock, and crops
Infrastructure
• Roads and railroads
• Gas and electric
Ecosystem assets
Water supply and water quality
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Characterize Risk of flooding
California
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Harm to the Ecosystem
Water Supply
Disruption
Damage to Delta as a
place
Expected Annual
Fatalities (EAF)
Expected Annual
Damage (EAD)
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Estimating Composite Risk in California
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FLOOD DAMAGE RISK (EAD)
ECOSYSTEM HARM
LIFE LOSS RISK (EAF)
WATER SUPPLY DISRUPTION
DAMAGE TO DELTA AS A PLACE
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California results
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California results
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• Identified high risk islands
• Set priorities for levee investment
• Recommended complimentary actions
• Did not use risk analysis to set levee heights
• Did not set TRG
• Amended the Delta Plan
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Characterize Risk of flooding
Netherlands
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Expected Annual
Fatalities (EAF)
Expected Annual
Damage (EAD)
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Dutch approach more comprehensive
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Dutch approach more comprehensive
• Tolerable individual life risk: 1 in 100,000 annual chance of dying from a flood
• Higher standard in areas of high “societal risk”
• Benefit-cost determines levee height
• Investment priorities determined by economic efficiency
• Multi-layered safety (nonstructural) where cannot justify levee investment
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Using risk analysis
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What actions to take?
Recognize intolerable risks
Flood risk management of the hazard and the consequences
Life safety
Allocate scarce resources
Residual risk
What is the risk? Where is it the greatest?
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For more information
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http://www.hse.gov.uk/risk/theory/r2p2.pdf
HSE Reducing Risks, Protecting People)
http://www.iwr.usace.army.mil/Portals/70/docs/iwrreports/10-R-8.pdf
Exploration of Tolerable Risk Guidelines
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For more information
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Delta Levees Investment Strategy
http://deltacouncil.ca.gov/delta-levees-investment-strategy
http://cedb.asce.org/CEDBsearch/record.jsp?dockey=0432079
Civil Engineering, September 2016
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F-N PLOTS
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FR
EQ
UE
NC
Y
OF
AN
AD
VE
RS
E
EV
EN
T
CONSEQUENCES
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F-N PLOTS
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FR
EQ
UE
NC
Y
OF
AN
AD
VE
RS
E
EV
EN
T
CONSEQUENCES
NOT TOLERABLE
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F-N PLOTS
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FR
EQ
UE
NC
Y
OF
AN
AD
VE
RS
E
EV
EN
T
CONSEQUENCES
NOT TOLERABLE
TOLERABLE
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F-N PLOTS
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FR
EQ
UE
NC
Y
OF
AN
AD
VE
RS
E
EV
EN
T
CONSEQUENCES
NOT TOLERABLE
TOLERABLE
Limit of Tolerable Risk
(judgement)
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F-N PLOTS
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FR
EQ
UE
NC
Y
OF
AN
AD
VE
RS
E
EV
EN
T
CONSEQUENCES
CURRENT RISK
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F-N PLOTS
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FR
EQ
UE
NC
Y
OF
AN
AD
VE
RS
E
EV
EN
T
CONSEQUENCES
CURRENT RISK
LEVEES DETERIORATE
POPULATION GROWS
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F-N PLOTS
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FR
EQ
UE
NC
Y
OF
AN
AD
VE
RS
E
EV
EN
T
CONSEQUENCES
CURRENT RISK
IMPROVE LEVEES
IMPROVE
EVACUATION
LEVEES DETERIORATE
POPULATION GROWS
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If you can measure risk, you can measure the cost-effectiveness of efforts to reduce risk
Other benefits of risk analysis & TRG
Recognizes
• Risk cannot be eliminated
• Absolute protection is not possible
Enables
• Evaluating effectiveness
• Allocate scarce resources
• Establishing priorities
• Fair treatment
• Equal consideration of structural + nonstructural flood management tools
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Characterize Risk
• Inventory assets and hazards
• Calculate EAF and EAD
• Evaluate socio-economic measures
• Where is risk the greatest?
• Are any risks intolerable?
Life safety concerns
Critical infrastructure
Historic places
Endangered species
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Identify Options to Reduce Risk
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• Structural
• Nonstructural
• Crisis management
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Natural and Nature-based Features
Identify Options to Reduce Risk
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Evaluate Options
• How well do measures reduce risk?
• How the cost-effective are risk reduction options?
• What is the level of residual risk?
• Is the residual risk tolerable?
• What are the trade-offs?
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Continuously Review & Communicate Risks
• Communicate
Decision-makers
Stakeholders
Public
• Review and adjust to changing conditions
Population
Infrastructure
Hydrology, SLR
• Provide OMRR & R
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