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

SUPPORT SCIENCE NEWS

Science News is a nonprofit.

Help us keep you informed.


News in Brief

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.

Sponsor Message

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 Administration, and population density maps from the Environmental Protection Agency. By combining these data, the researchers found that about 40 million people in the United States live in 1-in-100-year risk zones, three times as many people as FEMA’s estimate. A paper based on this work is in review at Environmental Research Letters.

Based on estimated future land development in the country, the number of people in a 1-in-100-year floodplain zone will climb to 60 million by 2050, and to 75 million by 2100, the team reported. But those figures account only for development in areas currently at risk, Wing says. As the planet continues to warm, rainfall patterns around the globe will shift — and some parts of the United States will see their flood risks rise.

Citations

O. Wing et al. Estimates of present and future flood risk in the conterminous United States. American Geophysical Union fall meeting, New Orleans, December 11, 2017.

C.C. Sampson et al. Validation of a 30m resolution flood hazard model of the conterminous United States. American Geophysical Union fall meeting, New Orleans, December 12, 2017.

A. Smith et al. Large scale flood risk analysis using a new hyper-resolution population dataset. American Geophysical Union fall meeting, New Orleans, December 11, 2017.

Further Reading

L. Hamers. Climate change is shifting when Europe’s rivers flood. Science News. Vol. 192, September 2, 2017, p. 14.  

T. Sumner. Gravity variations foretell flood risk months in advance. Science News. Vol. 186, August 9, 2014, p. 20.

Get Science News headlines by e-mail.

More from Science News

From the Nature Index Paid Content