CHALLENGE

Connecting flood exposure to individual property values at a national scale

Flooding is one of the costliest climate-related hazards in the United States, yet its financial implications remain difficult to measure at the individual property level.

Traditional flood maps, including FEMA's designated flood zones, provide an important regulatory baseline but don't capture every property exposed to flooding. As a result, housing prices may not fully reflect the financial risks associated with a property's location.

This creates uncertainty for buyers, lenders, insurers, and local governments that rely on accurate property valuations to make financial and planning decisions.

To investigate the scale of potentially unpriced flood risk, Boston University's Places Lab needed to combine detailed flood hazard models with property attributes, tax assessments, and market valuations across the country.

Doing so required a consistent nationwide parcel dataset that could connect these different sources of information to individual properties.

SOLUTION

Standardized nationwide parcel data connects flood models with property valuations

Through Regrid's Data With Purpose program, Boston University's Places Lab used Regrid's nationwide parcel data as a common spatial foundation for its research.

Regrid's standardized parcel boundaries and attributes enabled researchers to connect residential properties with high-resolution flood models developed by the First Street Foundation, alongside tax and property valuation information.

Using this integrated dataset, the team could estimate how flood exposure affects residential property values and compare those estimates with prevailing market prices.

Regrid's consistent parcel structure was particularly important for conducting the analysis across all 50 states, allowing researchers to work with property information from different jurisdictions within a common framework.

By connecting flood hazards with individual properties and their economic characteristics, the team could investigate the financial implications of flood exposure at a level of detail that broader geographic analyses could not provide.

RESULTS

Revealing $187 billion in residential overvaluation and widespread overlooked flood exposure

The research identified an estimated $187 billion in residential property overvaluation associated with flood risk that is not fully reflected in market prices.

By linking 14.6 million residential properties to detailed flood models, the team also found that 83% of the at-risk homes identified in the study were located outside FEMA's 100-year flood zones.

The findings revealed significant geographic disparities. Although unpriced flood risk exists across the country, the South and Southeast showed the greatest concentration, while lower-income counties were found to be particularly vulnerable.

These insights have implications well beyond academic research. For banks and lenders, understanding potential overvaluation can inform property risk assessments and lending decisions. Insurers can use more detailed flood exposure information to better understand the risks associated with individual properties.

For municipalities and policymakers, the findings highlight potential vulnerabilities in local property tax bases, infrastructure planning, and communities that may face disproportionate financial impacts from flooding.

By providing the parcel-level foundation needed to connect environmental hazards with economic data, Regrid helped researchers reveal risks that conventional flood maps and broader market analyses can overlook.

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