Underwater: Rising Seas, Chronic Floods, and the Implications for US Coastal Real Estate 

The Union of Concerned Scientists (UCS) researched the impact of sea level rise tidal flooding on coastal real estate, for the entire coastline of the lower 48 states. The study identified the number of residential and commercial properties at risk of chronic inundation, including the total current property value, estimated population, and property tax base affected. UCS determines that some coastal real estate markets will not likely recover under high future GHG emissions scenarios in which sea levels rise greatly; and the number of properties facing chronic inundation is much reduced under low emissions scenarios. Interactive maps are available that show the results of this study, including how many homes are at risk by state, community, and ZIP Code.

This resource was featured in the June 28, 2018, ASAP Newsletter.

"The latest Union of Concerned Scientists report examines the impact of worsening tidal flooding caused by sea level rise on coastal real estate. According to the report, up to 311,000 homes are at risk of chronic flooding within the next 30 years—the lifespan of a typical mortgage. By 2100, as many as 2.4 million homes could be at risk—roughly the equivalent of Los Angeles and Houston combined.."

The analysis estimates the number of homes and commercial properties in the coastal U.S. that will face chronic, disruptive flooding - defined as flooding that occurs 26 times per year or more. This flooding is from higher high tides, or higher sea levels, rather than from storms or storm surge inundation. Under a high sea level rise scenario, UCS found that within the next 15 years approximately 147,000 existing homes and 7,000 commercial properties - currently worth $63 billion - are at risk of chronic flooding. More than 300,000 of today’s properties at risk within the next 30 years, and the cumulative current value of the properties that will be at risk by 2045 is estimated at around $136 billion.

However, with a low sea level rise scenario, by the year 2060, the analysis finds that the number of homes at risk of chronic inundation would be reduced by nearly 80%, from 625,000 to 138,000.

The report identifies “Hotspots of Risk” in Louisiana, Maryland, North Carolina and New Jersey based on poverty levels, racial inequities and increased coastal flooding. Two metrics to identify communities that may have fewer resources to cope with chronic flooding were used for this assessment - poverty rate and the percentage of the community composed of traditionally underserved groups - African Americans, Hispanic Americans, and tribal communities. Of the nearly 175 communities nationwide that are projected to have significant chronic flooding by 2045, approximately 40%, or 67 of these communities currently have poverty levels above the national average. The majority of these is in Louisiana, where there are 25 communities with above-average poverty rates and 10% or more of the homes at risk by 2045.

The report describes the financial losses that homeowners and commercial property owners face if their properties flood regularly. As flooding becomes more frequent, the value of flooded homes will decline and mortgages could exceed the value of the home, homes will be increasingly difficult to insure, and could be in a deteriorated condition from flooding beyond repair. Additionally, declining property values could erode the tax base for communities. These risks and more are detailed for: Homeowners and Business Owners, the Local Tax Base, and for the Wider Economy - Lenders, Taxpayers, Developers and Investors.   

UCS also identifies methods to reduce these risks to communities under the following categories:

  • State and local policymakers must help disseminate flood risk information to communities, and set local zoning and building regulations in line with these risks.
  • The federal government must play a lead role in communicating risks to the public and incorporating those risks into its own policies and actions.
  • Flood-risk disclosure in the marketplace is vital to help individuals and businesses understand the risks to their investments and drive more resilient outcomes.

To determine the number of coastal properties at risk from this level of chronic flooding, the analysis uses property data from the online real estate company Zillow combined with the findings of the 2017 analysis When Rising Seas Hit Home: Hard Choices Ahead for Hundreds of US Coastal Communities, which uses a peer-reviewed methodology to assess areas at risk of chronic inundation.


Publication Date: July 2018

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Resource Types:

  • Assessment
  • Policy analysis/recommendations


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