SMAR Daily Industry News

Many Homes Face Flood Risk Even Outside FEMA Zones

A recent study published in Applied Geography reveals that a substantial number of homes in Houston are at risk of flooding despite being located outside FEMA’s 100-year flood zones. Researchers from Arizona State University, the University of Colorado Boulder and local scholars built a flood-risk score for nearly one million residences, combining parcel-level flood depth estimates, building age and condition, nearby traffic volume and financial exposure.

The analysis found that flood-risk scores varied more between individual houses on the same street than between different neighborhoods. This means that neighborhood-average flood maps can mask the presence of some of the county’s most vulnerable homes, while other homes in high-risk areas may be well protected.

Four key factors drive a home’s vulnerability. First, the projected water depth from a 100-year flood event was taken from a national flood model for each parcel in Harris County. Second, building data from county appraisal records identified older, lower-quality structures in poor repair. Third, traffic density within half a mile and three miles of each home measured mobility challenges that affect evacuation and emergency response. Fourth, financial metrics captured estimated repair costs and the proportion of nearby homes with flood insurance, reflecting recovery capacity.

Earlier work by the same team showed that more than half of 100,000 documented flood-prone buildings in Houston lie outside official flood boundaries, and these overlooked structures are more likely to be in disrepair and uninsured. The new house-by-house approach helps pinpoint exactly where limited public funds for flood-proofing, drainage improvements and post-event assistance should be directed.

Homeowners can use the study’s findings to assess their own risk. Practical steps include checking local flood-plain offices for past inundation records, reviewing property age and condition through public appraisal data, evaluating whether daily routes to work or school flood, and confirming whether they carry a separate flood insurance policy, as standard homeowner policies typically exclude flood damage.

Municipalities can adopt the researchers’ methodology by integrating existing address-level flood scores with local building, road and insurance data. By focusing on the granular factors that influence damage, officials can allocate scarce mitigation resources more effectively, targeting the homes that are truly at greatest risk rather than relying on broad neighborhood averages.

Why it matters

Understanding individual home flood risk helps insurers, homeowners and local officials allocate protection and recovery resources more precisely.

FAQ

How many homes are estimated to be at risk beyond FEMA’s flood maps?
About 6 million more homes, and 14.6 million properties in total, are estimated to be at risk according to one estimate.

What four factors did the study use to score flood vulnerability?
The study combined projected flood depth, building age and condition, nearby traffic volume, and financial exposure including repair cost and insurance coverage.

Did the study find more variation in risk within neighborhoods or between them?
Risk scores differed more from house to house within a neighborhood than between neighborhoods.

What practical steps can homeowners take to assess their flood risk?
Homeowners can check local flood-plain records, review property age and condition, evaluate flood-prone routes, and verify if they have flood insurance.

Source: Insurance Journal. See the original source for full details.