The Cost of Climate: America’s Growing Flood Risk
In February 2021, the First Street Foundation released a report -- The Cost of Climate -- that analyzes the financial risks and economic impacts of flooding across the country. As a whole, the report estimated losses from current and future flood risks to residential properties in the contiguous United States. Current annual flood losses are estimated to be around $20 billion. With sea-level rise and increased freshwater flooding from climate change, these annual flood losses are estimated to increase by 61% to $32 billion by 2051. The analysis was conducted at the census tract scale. State by state and detailed flood estimates are presented in the report.
The report finds that the greatest current flood risks are in coastal areas. Florida, California, South Carolina, Texas, and Louisiana have the largest total flood losses. The states with the greatest flooded losses as a share of property values are Delaware, South Carolina, West Virginia, and Florida. The lowest total flood damages are in the Great Plains states of North Dakota, Kansas, and Nebraska.
Using an alternative metric based on flood risk relative to National Flood Insurance Program premiums, Delaware, South Carolina, and Washington have the highest relative risks, while Kansas, Nebraska, and North Dakota have the lowest relative risks.
The report found that climate change is likely to cause greater increases in economic risks in counties that are prepared for current levels of flooding, but that are not yet prepared for future increases in flood risk. Coastal states face the greatest increase in economic risk from climate change and sea-level rise, especially Louisiana, South Carolina, Texas, Florida, and Mississippi. Inland states, led by Colorado, Missouri, and Tennessee also face increased economic losses from increased flooding but the risks are lower than those facing coastal states.
The report presents results for each of the contiguous 48 states displaying results by county for:
- estimated value of current flood losses,
- where climate change is estimated to increase flood losses the most, and
- relative property losses versus NFIP premiums.
The First Street Foundation used publicly available and private data sources on location and topography of more than 25 million residential properties (including single family homes and 1-4 unit residential buildings) in the contiguous U.S. to estimate current and future flood risks in individual census tracts. Flood frequencies between 1-in-2- and 1-in-500-year-events were estimated for current climate conditions and climate conditions in 2051. The estimates incorporate projected increases in sea-level rise, change in hurricane intensity and location, and change in precipitation patterns and river flow. The climate projections used RCP 4.5, which is one of the lowest climate warming scenarios used by the Intergovernmental Panel on Climate Change and would require substantial reductions in greenhouse gas emissions from current levels.
Publication Date: February 2021
- First Street Foundation