earthea nance, phd, pe, cfm assistant professor, university of new orleans research associate,...
TRANSCRIPT
Earthea Nance, PhD, PE, CFMAssistant Professor, University of New OrleansResearch Associate, Dillard University-DSCEJ
Presented at the HBCU Student Climate Change ConferenceDillard University April 6, 2013
Flood Risk Management in the Age of Climate Change
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How can flood hazards be
managed in a changing climate?
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Natural HazardsNatural Hazards
Hazards do not become disasters until they collide with the human, or “built”, environment.
“Floods are acts of nature, but flood losses are largely acts of man.”
Gilbert White
Joel Gratz © 2006
Miami Beach, 1926 and 2006Miami Beach, 1926 and 2006
Wendler Collection
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Flood Risk = Probability x ConsequenceFlood Risk = Probability x Consequence
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“Hazard mitigation means any sustained action taken to reduce or eliminate the long-term risk to human life and property from hazards.”
Source: US Code of Federal Regulations (44 CFR 201.2)
“Mitigation is the effort to reduce loss of life and reduce loss of life and property by lessening the impact of disastersproperty by lessening the impact of disasters. This is achieved through risk analysis, which results in information that provides a foundation for mitigation activities that reduce risk, and flood insurance that protects financial investment.”
Source: FEMA (www.fema.gov/government/mitigation.shtm#1)
Hazard MitigationHazard Mitigation
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“Adaptation is adjustment in ecological, social, or economic systems in response to actual or expected climatic stimuli and their effects or impacts......It involves adjustments to reduce the vulnerability of adjustments to reduce the vulnerability of communities, regions, or activities to climatic change communities, regions, or activities to climatic change and variability.”
Source: IPCC Fourth Assessment Report, WGII (2007)
Adaptive CapacityAdaptive Capacity
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“Disaster resilience is the capacity of a community exposed to hazard to adapt, by resisting or changing, in order to reach and maintain an acceptable level of functioning and structure.”
Source: Cutter, et al, CARRI Research Report I (2008)
“The ability of a system and its component parts to ability of a system and its component parts to anticipate, absorb, accommodate, or recover from the anticipate, absorb, accommodate, or recover from the effects of a hazardous event effects of a hazardous event in a timely and efficient manner...”
Source: IPCC, Managing the Risks of Extreme Events…(2012)
Disaster ResilienceDisaster Resilience
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Climate ChangeClimate Change
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Increased Mean TemperatureIncreased Mean Temperature
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Increased Temperature VariabilityIncreased Temperature Variability
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Changing Probability DistributionChanging Probability Distribution
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Frequency of heavy precipitation will increase (66-100% probability).
Average tropical cyclone wind speed will increase (66-100% probability).
Frequency of cyclones will either decrease or remain the same (66-100% probability).
Mean sea level will rise (90-100% probability). Areas currently experiencing coastal erosion Areas currently experiencing coastal erosion
and flooding will continue on an upward trend and flooding will continue on an upward trend (90-100% probability).(90-100% probability).
Climate ChangeClimate Change
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Result = Increased Probability andResult = Increased Probability and Severity of Flooding Severity of Flooding
Estimated Total Flood Damages in the United States, 1934-2011 (Billions)
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Riverine and coastal flooding accounts for 75% flooding accounts for 75% of all federal disaster declarationsof all federal disaster declarations, present in all 50 states, total of $471 Billion in flood damages since 1903 and rising (10% of this 2005 alone).
Flood risk is measured as the standard 100-year base flood (1% annual chance). This represents the damage worth protecting and the risk worth accepting without excessive cost to property owners. Established as the US formal standard by Executive Order 11988 in 1977. Reconfirmed by FEMA in 1983.
Flood Risk in the USFlood Risk in the US
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Floods and other hydrological events accounted for over 50% of all disasters over 50% of all disasters between 2001 and 2010.
About 800 million people live in flood-prone areas, and about 10% are annually exposed to floods.
Floods interrupt food and water supplies, affect economic development, and cause acute and long-term health impacts.
Flood Risk around the WorldFlood Risk around the World
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Areas Most SusceptibleAreas Most Susceptible
The severity of flood impact depends strongly on the The severity of flood impact depends strongly on the level of exposure and vulnerability.level of exposure and vulnerability.
Increased population and property values in coastal coastal areas areas of the US and Caribbean increases exposure and vulnerability. Sea level rise and land subsidence compounds the surge impacts of tropical cyclones.
Informal settlements Informal settlements made of weak building materials and located in drainage areas and riverine floodplains have increased exposure and vulnerability to flash floods.
Tropical small island states Tropical small island states in the Pacific, Indian, and Atlantic Oceans are exposed to rising seas and are vulnerable to coastal erosion, ecosystem disruption, economic loss, population displacement.
Committee on Levees and the National Flood Insurance Program
National Research CouncilWater Resources and Technology Board
Levees and the National Flood Insurance Program:
Improving Policies and Practices
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Mississippi River Levee (Source USACE)
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Flood RiskFlood Risk
Flood risk is a function of:
•the characteristics of the hazardhazard,
•the exposureexposure to the hazard,
•the vulnerabilityvulnerability of that which is exposed, and
•the consequencesconsequences that could occur.
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Flood Risk AnalysisFlood Risk Analysis
An analytical process quantifying probabilities and quantifying probabilities and consequences of a flood event.consequences of a flood event.
Current US approachEstablishes a level of protection (100-year).Assumes accredited levees withstand floods Assumes accredited levees withstand floods and
non-accredited levees do not withstand floods.Computes expected water elevation of 100-yr flood.Accounts for uncertainty through freeboard
requirement.Ignores residual risk behind leveesIgnores residual risk behind levees.
Move to comprehensive risk analysis implemented by the Army Corps’ IPET Task Force in 2006 in response to Hurricane Katrina.
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Hurricane Katrina - Approximately 515,000 homes were destroyed (320,000 in New Orleans Metro) and over 50 major levee breaches were discovered.
The levee system was de-accredited and it became clear that the existing flood maps seriously flood maps seriously understated flood risk.understated flood risk.
It was discovered that the levees were not only damaged by the storm, but had been improperly improperly designed and constructeddesigned and constructed.
National flood insurance program went bankruptflood insurance program went bankrupt. The Army Corps established an Interagency Interagency
Performance Evaluation Task Force (IPET) to Performance Evaluation Task Force (IPET) to analyze the flood risk using best available science.analyze the flood risk using best available science.
Flood Risk AnalysisFlood Risk Analysis
State-of-the-Science Flood Risk Analysis
Modern flood risk analysis employs recent advances in hydrology, meteorology, geotechnical engineering, 3D hydrodynamic modeling, and computational mapping to evaluate the probability of :•Flood events ● Levee Performance ●
Consequences
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Evolution of Flood Risk ManagementEvolution of Flood Risk Management
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≈30,000 Miles of Levees (FEMA 2012)
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MitigationMitigation
Multiple lines of defense.
Levees.
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Coastal Wetlands Levee/Pumping/Drainage Systems Total Water Management Neighborhood Drainage Elevation in Place Flood-proofing Secondary Levees/Polders Structure Relocation Permitting Decisions Building Code Enforcement Evacuation Planning Disaster Warning System Flood Insurance
Flood Risk ManagementFlood Risk Management
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Flood Risk Management
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Risk Communication: Mapping
• Technological advances have opened the door for vastly improved flood risk mapping.
• Provides an opportunity for better communication of flood risk .
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Emerging Policy ApproachesEmerging Policy Approaches
◊ FEMA Digital Flood Insurance Rate Maps FEMA Digital Flood Insurance Rate Maps now use IPET risk modeling results. Significant changes to flood zones, esp. coastal areas.
◊ National Flood Insurance Reform Act of 2012 National Flood Insurance Reform Act of 2012 eliminates subsidies and grandfathering; imposes actuarial flood insurance rates and national rate increases. Hits 2nd homes, older homes, non-compliant homes, and new purchases first.
◊ Maps + Rates = Imposed AdaptationMaps + Rates = Imposed Adaptation.
◊ Risk communication remains poor.
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How are we Managing Flood Risk?How are we Managing Flood Risk?
◊ Hurricane Katrina and the levee failure initiated a series of national changes in flood risk management. Better levees and better flood risk Better levees and better flood risk analysis came first. Better flood maps and actuarial analysis came first. Better flood maps and actuarial insurance rates are next.insurance rates are next.
◊ So far there has been little to no communication little to no communication about insurance changes to the public by Congress or FEMA. They are leaving this to local officials.
◊ Consequences disproportionately impact coastal Consequences disproportionately impact coastal communities communities who have already had to adapt to the impacts of hurricane surge, the oil/gas industry, navigation, and urban development.
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How can flood hazards be managed in a changing climate?
1.Use best available science to estimate risk.2.Use multiple lines of defense to mitigate.3.Better communicate the actual risk.4.Better adapt through policy changes that reduce exposure and vulnerability.
ConclusionsConclusions
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Little to no investment in relocation of communities exposed to flooding.
Not enough investment in levees & land use planning to protect communities exposed to flooding.
Too-little-too-late investment in coastal restoration. Limits of adaptation in coastal communities.
Are coastal communities the new sacrifice zones?
orHave we created too many vulnerable
communities in coastal areas?
Closing ThoughtsClosing Thoughts
