AECOM conducted the Climate Change Study for FEMA to analyze potential long-term implications of climate change on the NFIP. The climate change impact assessment includes all 50 states, as well as consideration of the U.S. territories.

However, since the concern is impact on the NFIP as a whole, it is recognized that not all regions have the same relative significance. A detailed region-by-region assessment of climate change was not intended. Major attention, therefore, was given to areas of greatest population and the largest inventory of at-risk properties.

FEMA intends to use the findings of this study to assist in the development of recommendations addressing the impacts of climate change and future development on Flood Insurance Rate Maps (FIRMs).

Download and read the study, “The Impact of Climate Change and Population Growth on the National Flood Insurance Program.”

Summary of Technical Findings

  • In riverine environments, by the year 2100, the relative increase in the median estimates of the 1 percent annual chance floodplain (floodplain) depth and area (Special Flood Hazard Area or SFHA) is projected to average about 45% across the nation, with very wide regional variability.
  • In coastal environments, assuming a fixed shoreline, the typical increase in SFHA is projected to be about 55% by the year 2100, with very wide regional variability. Using the receding shoreline assumption, negligible change in coastal SFHA is projected. This is because the amount of new coastal SFHA resulting from rising sea levels will be equally offset by the land area lost to sea level rise-induced inundation and erosion, when averaged over time and shoreline length.
  • The national average increase in SFHA by the year 2100 may approximate 40% for riverine areas and coastal areas if shoreline recession is assumed; and 45% for riverine areas and coastal areas if fixed coastlines are assumed.

Summary of Economic Findings

Riverine and Receding Coastal Shorelines

  • The total number of NFIP insurance policies may increase by approximately 80% by 2100. The number of riverine policies may increase by about 100%, and the number of coastal policies may increase by approximately 60%.
  • The average loss cost per policy may increase approximately 50% by the year 2100.

Riverine and Fixed Coastal Shorelines

  • The total number of NFIP policies may increase by approximately 100% by the year 2100. The number of riverine policies may increase by approximately 80%, and the number of coastal policies may increase by 130%.
  • The average loss cost per policy may increase approximately 90% by the year 2100.

The figure, Median Projected Percent Change in Special Flood Hazard Area for 2100 Over Current Conditions, shows the median projected percent change in the Special Flood Hazard Area for 2100 over current conditions.

Review Panel

A team of experts from the engineering, climate science, and insurance sectors played a key role in the study through a process of methodology and report review and comment as well as assistance identifying and obtaining data. Panel members included federal agency representatives, state floodplain representatives, and independent experts.

“I appreciate the transparency of your explanation of your methods. I think that is the real strength of what you’ve done… I would commend you on that.” – William Gutowski, Iowa State University, review panel member

USGCRP Review

Prior to its release, a draft of the report was reviewed, though not necessarily endorsed, by experts from other federal agencies. Prominent among them was the review by the U.S. Global Change Research Program (USGCRP). Four anonymous reviewers, one each from USGS, EPA, DOE and NOAA, commented on the final draft report as a part of USGCRP review. These individuals conveyed, strongly and unanimously, that they felt, as a scoping-level study, this report is a solid piece of work and that, furthermore, as representing a concrete step towards adaptation, it should be released at the earliest opportunity.

Publications and Presentations

  • American Society of Civil Engineers, ASCE Journal of Water Resources Planning – “Estimating the Impacts of Climate Change and Population Growth on Flood Discharges in the United States,” J.B. Kollat, J.R. Kasprzyk, W.O. Thomas, A.C. Miller, and D. Divoky
  • ASCE Council on Disaster Risk Management Monograph No.6, Sea level rise and coastal infrastructure; prediction, risks and solutions 2012 (pp. 59-77) –  “The impact of climate change on the National Flood Insurance Program,” D. Divoky, S. Eberbach, and M. Crowell
  • American Water Works Association (AWAA) New Jersey Local Chapter, “Flood Events: Are We Prepared for the New Normal,” Manalapan, New Jersey, September 27, 2012
  • National Conference on Ecosystem Restoration (NCER), “Planning for the Impact of Climate Change for FEMA’s National Flood Insurance Program,” Baltimore, Maryland, August 1-5, 2011
  • American Society of Civil Engineers (ASCE) Environmental and Water Resources Institute (EWRI) World Environmental & Water Resources Congress, “Estimating the Impacts of Climate Change and Population Growth on Flood Discharges in the United States,” Palm Springs, California, May 22-26, 2011
  • 28th Annual National Flood Conference, “Impact of Climate Change on the National Flood Insurance Program,” New Orleans, LA, May 1 – May 4, 2011
  • American Water Resources Association (AWRA), Specialty Conference on Managing Climate Change Impacts on Water Resources: Adaptation Issues, Options, and Strategies, “Using Projections of Extreme Climate Indicators and Their Uncertainty to Predict the Impact on Riverine Flooding in the United States,” Baltimore, Maryland, April 18-20, 2011
  • Hydro Vision International Conference, “Using Uncertain Projections of Extreme Climate Indicators to Quantify the Effects of Climate on Extreme flooding in the United States: Climate Change: New Challenges and Opportunities for Hydropower, Charlotte, North Carolina, July 27-30, 2010
  • Association of State Floodplain Managers (ASFPM) 34th Annual Conference, “Evaluating the Impact of Climate Change on the National Flood Insurance Program,” Oklahoma City, OK, May 16‑21, 2010
  • American Water Resources Association (AWRA) Annual Conference, “Coastal Flood Risk: Estimating the Influence of Climate Change,” Seattle, Washington, November 12, 2009
  • Maryland Association of Floodplain and Stormwater Managers (MAFSM) Annual Conference, “An Uncertainty Based Framework for Quantifying the Effects of Climate Change on Extreme Event Flooding in the United States,” Linthicum, MD, October 22, 2009
  • Proceedings of Coastal Zone 09, “Evaluating the Impact of Climate Change on the National Flood Insurance Program,” Boston, Massachusetts, July 19 to 23, 2009
  • AECOM Webinars
    • Joshua Kollat, “Using Uncertain Climate Change and Population Growth Projections to Estimate Changes in Extreme Event Flooding in the United States,” April 14, 2010
    • David Divoky, “Coastal Flooding and Climate Change,” March 22, 2011

Project Team

The study was led by AECOM with support from Michael Baker Jr., Inc., and Deloitte Consulting, LLP. The project team was led by two eminent technical experts, the late David Divoky and Dr. Arthur Miller with support from Wilbert Thomas, Jr. and Susan Pino. Scott Edelman served as principal-in-charge of the project with support from project manager Perry Rhodes and assistant project manager Manas Borah.

Mark Crowell served as FEMA’s task leader, providing general oversight of the project. Roy Wright, deputy associate administrator for FEMA’s Mitigation Directorate and Doug Bellomo, Risk Analysis Division director, also provided critical comments and suggestions.

The study was sponsored by FEMA and was recommended by the Government Accountability Office (GAO) in its March 2007 report titled “Climate Change: Financial Risks to Federal and Private Insurers in Coming Decades are Potentially Significant.”

Dedication

This report is dedicated to the memory of David Divoky, who played a pivotal role in getting the team to collaborate creatively and develop innovative, simple solutions to carry out the analysis.

Contact Information

All questions concerning this study should be directed to:

Art Miller, AECOM, (814) 571-0486, Art.Miller@dev-aecom.pantheonsite.io