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International Approaches to Floodplain Management:
Making more informed decisions using risk information
Netherlands New Zealand France
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Alternate title…
Jessica, Anna, and David go on vacation!
Netherlands New Zealand France
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Today’s Session
International Approaches to Floodplain Management
Risk-informed decision making and int’l examples
Jessica Ludy
Useful information provided by different types of regulatory flood maps in the European Union
Anna Serra Llobet
Applying risk-informed floodplain management lessons from overseas in the U.S. A
David Powers
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NFIP has been successful in reducing some flood
losses in communities since 1968, but it falls short.
Goal: We must provide additional tools to
stakeholders (and the public) make better
floodplain management decisions
“(2P+2R)(PPR)= Resilience” (Judge Emmett)
Today’s Session
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Using tolerable risk guidelines to manage flood risk
Image: Associated Press, Gizmodo.au Sept 16. 2017
Jessica Ludy, CFM (ESA)
Larry Roth, PE;GE (Arcadis)
ASFPM 2018: Phoenix
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Today’s discussion
• What is risk and tolerable risk?
• How to use risk analysis in floodplain management
• International Examples
• Takeaways
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What is risk?
•
7June 27, 2018© Arcadis 2015
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What is Risk?
What is the
hazard and how
likely is it to
occur?
Who and what are
in harm’s way?
How vulnerable are
they to harm?
How much harm will
be caused?
Image adapted from HR Wallingford and Anna Serra Llobet
What is the
pathway of hazard
to the receptor?
how will
infrastructure
perform?
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What is risk?
Risk = Probability x Consequences
Image adapted from HR Wallingford and Anna Serra Llobet
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How do we measure risk?
Loss of life: Expected Annual Fatalities (EAF)
• Considers the probability of flooding
• Consequences of flooding:
− Number of individuals exposed to floodwaters
− Affected by warning time, water depth and velocity, rate of
rise, water temperature, etc.
10Image: Fox News Aug 27, 2017
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How do we measure risk?
Damage to property and infrastructure:
Expected Annual Damages (EAD)
11June 27, 2018
• Probability of flooding
• Consequences of flooding
• Assets, infrastructure
• Depth Damage curves
• Integrates the product of these over all flood levels
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Quantifying risk enables
• How much risk is there?
• Where risks are
greatest?
• What actions to take?
• Are risks tolerable? Is
more risk reduction
warranted?
How do we decide whether risks are tolerable?
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What is tolerable risk?
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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
15
ne 2018
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We make decisions everyday on what level of risk is tolerable to us
1627 June 2018
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With the NFIP, we tend to focus on the hazard
Risk = Probability x Consequences
Image adapted from HR Wallingford and Anna Serra Llobet
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And often ignore consequences
Risk = Probability x Consequences
Image adapted from HR Wallingford and Anna Serra Llobet
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LOP prevents discussion of how safe is safe enough?
Limitations of the NFIP approach
• Insurance standard
• Measures water level, not risk
• Implies risk can be eliminated
• Favors structural solutions
• Hard to measure
– Risk reduction
– Cost-effectiveness
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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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Lower Residual Risk
Flood Height (ft)Higher Residual Risk
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Ignoring residual risk has adverse
consequences
• Public safety
• Land use
• Infrastructure
investment
• Preparedness
21https://www.cbsnews.com/news/ellicott-city-maryland-flooding-today-2018-05-27-live-updates/
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Principles of Tolerable Risk
Life safety is paramount
Risk cannot be ignored
Absolute safety cannot be guaranteed
Equity and efficiency
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ALARP: As Low As Reasonably Practicable
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Tolerable risk guidance from other settings
Nuclear Power Plants Commercial Aviation
Dams Hazardous Occupations
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Tolerable Risk Guidance in the US
Best practices identified by
USACE and USBR (2015)
Manual encourages risk
assessment procedures (revised 2018)
24
Risk-informed planning
manual (revised 2017)
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How safe is safe enough?
A policy decision with expert input
• Informed by analysis, risk
assessment, and
communication
• Considers:
• Individual risks
• Societal risks
• Equity
252527 June 2018
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How to use risk analysis in FPM
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Applying risk analysis and tolerable risk principles
Identify Options to Reduce Risk • Structural• Non-structural• Nature-based• Calculate risk reduction
Characterize Risk• Inventory assets• Identify Hazards• Assess vulnerabilities• Calculate risk &
uncertainty
Implement Measures & Continuously Review
• Communicate risks• Adapt to change• Perform robust OMRR&R*
Evaluate Options• Do measures reduce risk to
tolerable levels?• Compare cost-effectiveness
measures, trade-offs• Assess residual risk
1.
2.
3.
4.
2727 June 2018
*Operations, maintenance, repair, replacement, and rehabilitation
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Advantages of a risk-informed approach over the NFIP approach
Facilitates
• Understanding risk
• Communicating risk
• Managing risk
Enables
• Evaluation of trade-offs and cost-effectiveness
• Allocating scarce resources
• Fair treatment
Recognizes • Risk cannot be eliminated
• Absolute protection is not possible
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International Examples of Risk-informed
Decision making
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Netherlands…a long history of flood prevention
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Flood of record informed contemporary
Dutch floodplain management
1953
North Sea
70,000 Evacuated
1,835 casualties
€450-680M damages
Where was Europe in
1953?
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Intolerable Risk: Never again!
Late 1950’s the Dutch
implemented loosely risk-
informed standards
− Higher levels of protection in
areas with greater number of
people and assets
− Lower levels of protection with
fewer people and assets
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Flood Prevention: “Dry feet”
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Still a “level of protection” policy of:
Flood control
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Flood control to flood risk management
Image adapted from HR Wallingford and Anna Serra Llobet
Recognizing increasing risk, Dutch flood policy
evolves
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Flood control to flood risk management
“Multi-layered safety”: Prevention, Protection, Preparedness
Image adapted from HR Wallingford and Anna Serra Llobet
Recognizing increasing risk, Dutch flood policy
evolves
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Netherlands sets risk-based safety standard
• Individual life risk standard:
1/100,000 chance of dying
from a flood per year.
• Higher safety standards in
areas of great “societal risk”
• Investment priorities
determined by economic
efficiency
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Netherlands sets risk-based safety standard
• Use “Multi-layered safety”
where levee investment
cannot be justified
• Use benefit-cost analysis to
determine levee height
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How the Dutch can meet risk-based standard
Image adapted from HR Wallingford and Anna Serra Llobet
EAF: 1/100,000 annual chance of dying from flood
• Option 1: Levee: 1/100,000 water level
• Option 2: smaller levee, 1/10,000 water level+ elevate +
evacuate for additional x 10
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Dutch Takeaways
• It is possible to shift a decades-old paradigm from flood
control to flood risk management
• Setting a risk-based standard (instead of probability based
standard) enables more flexibility with meeting safety
standards
• Using risk analysis enables a cost-effective and cost
efficient means of prioritizing actions and determining levee
heights
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New Zealand:
Franz Josef Glacier
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Flood risk management in New Zealand
New Zealand is highly exposed to multiple geologic hazards
Central government: emergency response
Local & regional governments: floodplain management and flood defense
No national “level of protection” standard
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Franz Josef Glacier
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Image: Jessica Ludy
Franz Josef Glacier
Waiho River
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Franz Josef Glacier: Tourism Hot Spot
− Population: 510• (444 rateable properties)
− Tourism
− Unesco World
Heritage Site
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Retreating glacier, alluvial fan, stopbanks
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Flooding March 2016
https://www.odt.co.nz/news/national/flooding-chaos-west-coast
“1meter of gravel through the hotel”
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Also… earthquakes.
Source: Natural Haz. Assessment for town of Franz Josef Glacierhttp://www.wcrc.govt.nz/Documents/Natural%20Hazard%20Reports/GNS%20Final%20Franz%20Josef%20Report%202016.pdf
Alpine Fault
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Risk-informed planning
1. Characterized Conditions
2. Analyzed Risk and
Vulnerability
3. Identified Possible Solutions
4. Evaluated and Compared
Solutions
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Characterize, Quantify Risk & Vulnerability
Hazards
• Earthquake
• Flood
• Landslide
Assets
• Infrastructure
• 510 people
• Tourism industry
• Unesco World Heritage
site
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Identify Options to Reduce Risk
Avoid risk
Manage Risk
Transfer Risk
Accept Risk
Reduce probability, or relocate
Reduce consequences
Reduce burden of risk
Requires stakeholder support/buy-in and communication
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Primary “Packages” (options)
Living with Nature’s Challenges
• Relocate main assets off of fault
• Allow the Waiho River more room, stop improving levees
Avoiding Nature’s Challenges
• Relocate the entire town
Defending against nature’s challenge
• Improve levees
• Remove gravel
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Evaluate Risk Reduction Options
• Risk Reduction
• Earthquake Risk
• Flood risk
• Landslide risk
• Disruption to community
• Investment certainty
• Cost (Benefit cost)
• Tradeoffs
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Top performers:
Living with Nature’s Challenges
Defending against nature’s challenge
Both require level of risk understanding, tolerance, and acceptance
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Next steps for Franz Josef Glacier
• Stakeholder groups
• Governance
• Decision
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Franz Josef Takeaways
• Quantifying risk enables evaluating alternatives for how
well they reduce risks
• And for whether or not they reduce ALL types of risk
• Communicating all risks and alternatives allows stakeholders to determine whether risks are tolerable as they are, or whether more action is warranted
• Given the costs
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Risk Analysis is applied in the United Kingdom
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A few examples of risk-informed FPM in California
• Tillman Reclamation Plant (CA)
• California Delta
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Conclusions and other Applications
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• Facilitates understanding, managing, and
communicating risk
− Whereas the NFIP only considers the hazard
• How safe is safe enough?
• Enables selection of measures from full suite of
options based on risk reduction and cost effectiveness
− If you measure risk, you can measure how well options
reduce risk;
• Promotes efficient use of public resources
• Recognizes that absolute protection is not possible
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Why use a risk-informed approach?
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Contacts:
c 916.740.0930
LARRY ROTH, PE, GE, ENV SPVice President, Arcadis
Phoenix, AZ
c 734.604.0282
JESSICA LUDY, CFMWater Resources Planner, ESA
San Francisco, CA