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U.S. Flood Risk Greatly Underestimated

A new study led by researchers at the University of Bristol in the United Kingdom has found that 41 million Americans are at risk from flooding rivers and streams, which is more than three times the current estimate of 13 million people based on existing regulatory flood maps. The new figure does not include the millions more Americans vulnerable to coastal flooding...
March 7, 2018

A new study led by researchers at the University of Bristol in the United Kingdom has found that 41 million Americans are at risk from flooding rivers and streams, which is more than three times the current estimate of 13 million people based on existing regulatory flood maps. The new figure does not include the millions more Americans vulnerable to coastal flooding.

The study is based on a high-resolution model that maps flood risk across the entire continental United States, whereas the existing regulatory flood maps produced by the Federal Emergency Management Agency (FEMA) cover about 60 percent of the continental United States. The study also integrates new maps from the Environmental Protection Agency that more precisely estimate where people live and where future population growth is expected.

The increase in numbers of those at risk is a result of the expanded coverage of the map combined with its ability to estimate flooding on small streams—something that wasn’t adequately captured in previous flood-risk models, according to the study’s researchers.

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