Vulnerable Cities: Coastal Flood Risk

U.S. cities’ annual coastal flood risks

Hurricane season along the Atlantic and Gulf coasts—June 1 through November 30–is approaching, elevating local coastal flood risks.

Sea level rise is making hurricane and coastal storm surges more dangerous and costly in U.S. cities. A Nature Communications study led by researchers from Climate Central showed that human-caused sea level rise accounted for $8.1 billion, or 13% of Hurricane Sandy’s damages in New York, New Jersey, and Connecticut. Northeastern cities face some of the highest sea level rise risks in the country, and those risks are projected to rise sharply in the coming decades.

Using data and maps from Risk Finder and Coastal Risk Screening Tool, Climate Central assessed annual coastal flood vulnerability—the likelihood of experiencing specific flood levels, and the impacts of each—for 23 U.S. cities. 

Vulnerable cities

The data for all 23 U.S. cities are available in this downloadable spreadsheet (.xlsx). Additional water levels can be explored at: riskfinder.climatecentral.org

Three key elements are provided across multiple potential water levels for each included city:

• likelihood of experiencing specific water levels within a year (selected for each city based on how much land is exposed to coastal flood risk, and the levels’ range of expected probability);

• the land area within the risk zone; 

• and links to dynamic maps for self-serve generation of visuals.

Select locations also have animated maps (YouTube) showing the change in vulnerable areas across multiple water levels.

Key terms

• Water levels – flood water level above Mean Higher High Water (MHHW), in feet.

• Likelihood – the expected probability of the location experiencing the given flood level (e.g., 3, 4, and 5 feet) in any particular year during the 2020s. Note that this probability accounts for all potential causes of increased water level, including storms other than hurricanes.

• Land area – area potentially exposed to the given flood levels, in square miles.

All data and maps can be customized through Risk Finder and Coastal Risk Screening Tool. 

Hurricanes and climate change

Research shows that atmospheric warming has increased the proportion of strong hurricanes (Category 4 and 5 storms) globally. And a recent study projects that climate change may increase the frequency of back-to-back hurricanes. Studies also suggest that warmer sea surface temperatures may enable hurricanes to strengthen more quickly—known as “rapid intensification.”

Additional reporting resources

• More Climate Central resources about tropical cyclones and hurricanes

• Tropical Weather & Climate Research at Colorado State University
  Annual extended range forecast of Atlantic seasonal hurricane activity

• NOAA and National Weather Service
  Tropical weather outlook 

Experts available for interview

Daniel Gilford, PhD
Climate Scientist
Climate Central
Contact: dgilford@climatecentral.org

If you have technical questions about Climate Central’s suite of sea level rise tools, please contact: Kelly Van Baalen, program manager, at kvanbaalen@climatecentral.org