Presentation on theme: "Earthea Nance, PhD, PE, CFM Assistant Professor, University of New Orleans Research Associate, Dillard University-DSCEJ Presented at the HBCU Student Climate."— Presentation transcript:
Earthea Nance, PhD, PE, CFM Assistant Professor, University of New Orleans Research Associate, Dillard University-DSCEJ Presented at the HBCU Student Climate Change Conference Dillard University April 6, 2013 Flood Risk Management in the Age of Climate Change
2 How can flood hazards be managed in a changing climate?
3 Natural 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
7 “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) reduce loss of life and property by lessening the impact of disasters “Mitigation is the effort to reduce loss of life and property 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 Mitigation
8 adjustments to reduce the vulnerability of communities, regions, or activities to climatic change “ 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 communities, regions, or activities to climatic change and variability.” Source: IPCC Fourth Assessment Report, WGII (2007) Adaptive Capacity
9 “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) ability of a system and its component parts to anticipate, absorb, accommodate, or recover from the effects of a hazardous event “The ability of a system and its component parts to anticipate, absorb, accommodate, or recover from the effects of a hazardous event in a timely and efficient manner...” Source: IPCC, Managing the Risks of Extreme Events…(2012) Disaster Resilience
14 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 and flooding will continue on an upward trend (90-100% probability). Climate Change
15 Result = Increased Probability and Severity of Flooding Estimated Total Flood Damages in the United States, 1934-2011 (Billions)
16 flooding accounts for 75% of all federal disaster declarations Riverine and coastal flooding accounts for 75% of 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 US
17 over 50% of all disasters Floods and other hydrological events accounted for 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 World
18 Areas Most Susceptible The severity of flood impact depends strongly on the level of exposure and vulnerability. coastal areas Increased population and property values in coastal 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 Council Water Resources and Technology Board Levees and the National Flood Insurance Program: Improving Policies and Practices 19 Mississippi River Levee (Source USACE)
20 Flood Risk Flood risk is a function of: hazardthe characteristics of the hazard, exposurethe exposure to the hazard, vulnerabilitythe vulnerability of that which is exposed, and consequencesthe consequences that could occur.
21 Flood Risk Analysis quantifying probabilities and consequences of a flood event. An analytical process quantifying probabilities and consequences of a flood event. Current US approach Establishes 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 levees Ignores residual risk behind levees. Move to comprehensive risk analysis implemented by the Army Corps’ IPET Task Force in 2006 in response to Hurricane Katrina.
22 Hurricane Katrina - Approximately 515,000 homes were destroyed (320,000 in New Orleans Metro) and over 50 major levee breaches were discovered. flood maps seriously understated flood risk. The levee system was de-accredited and it became clear that the existing flood maps seriously understated flood risk. improperly designed and constructed It was discovered that the levees were not only damaged by the storm, but had been improperly designed and constructed. flood insurance program went bankrupt National flood insurance program went bankrupt. Interagency Performance Evaluation Task Force (IPET) to analyze the flood risk using best available science. The Army Corps established an Interagency Performance Evaluation Task Force (IPET) to analyze the flood risk using best available science. Flood 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 23
24 Evolution of Flood Risk Management Willingness to live with floods Individuals and small communities adapt to nature’s rhythm. Desire to utilize the floodplain Fertile land in floodplain is drained for food production. Permanent communities are established on the floodplain. Demand for control of floods Large scale structural approaches are implemented. FEMA and Army Corps are the primary governmental organizations. Need to reduce flood damages A recognition that engineering alone has limitations. Effort is devoted to increasing the resilience of communities should a flood occur. Non-structural mitigation, natural functions, multiple lines of defence. A need to manage risk Recognize gradation of risk and damage. Risk management provides more precise information about flood risk. Neighborhood & household scale. Tailored approach yields better decisions on mitigation, rates, communication.
Risk Communication: Mapping Technological advances have opened the door for vastly improved flood risk mapping. Provides an opportunity for better communication of flood risk. 31
32 Emerging 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 Adaptation ◊Maps + Rates = Imposed Adaptation. ◊Risk communication remains poor.
33 How are we Managing Flood Risk? Better levees and better flood risk analysis came first. Better flood maps and actuarial insurance rates are next. ◊Hurricane Katrina and the levee failure initiated a series of national changes in flood risk management. Better levees and better flood risk analysis came first. Better flood maps and actuarial insurance rates are next. little to no communication ◊So far there has been 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 communities ◊Consequences disproportionately impact coastal communities who have already had to adapt to the impacts of hurricane surge, the oil/gas industry, navigation, and urban development.
34 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.Conclusions
35 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? or Have we created too many vulnerable communities in coastal areas? Closing Thoughts