Federal maps underestimate flood risk for tens of millions of people, scientists warn | Science News

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Federal maps underestimate flood risk for tens of millions of people, scientists warn

Researchers harnessed multiple types of data to come up with a new estimate

By
3:13pm, December 13, 2017
flooding in Louisiana

UNDER WATER  More than 60 centimeters of rain inundated parts of Louisiana (Baton Rouge shown) in August 2016, driving river gauges across the state to near-record levels and costing more than $10 billion in damages. New research suggests more areas in the United States are at risk for flooding than previously thought.

NEW ORLEANS — National flood maps are underestimating the risk for tens of millions of people in the United States. That’s the conclusion of researchers presenting a new study December 11 at the American Geophysical Union’s fall meeting.

The U.S. Federal Emergency Management Agency estimates that about 13 million people live in a “1-in-100-year” floodplain zone, a region that has a 1 percent chance of flooding in any given year. But the agency’s risk assessment largely focuses on larger streams and rivers, and lacks assessments of risk along smaller tributaries. FEMA’s calculations “miss a lot of the risk,” says Oliver Wing, a geographer at the University of Bristol in England.

Wing and his colleagues amassed a wealth of data, including the U.S. Geological Survey’s river gauge data, lidar measurements of land-surface elevation, rainfall data from the National Oceanic and Atmospheric

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