New model shows river flooding poses bigger risk

A new study finds that 41 million Americans are at risk of flooding from rivers, three times more than past estimates.

Regulatory flood maps produced by the Federal Emergency Management Agency only cover about 60 percent of the country, said Joe Fargione, science director for The Nature Conservancy's North America region based in Minneapolis. He said that leaves some people unaware they are in a flood-prone area.

"Flooding obviously takes a big human toll, and that's true even for people who have insurance," Fargione said. "But for those who don't realize they're at risk, they may be less likely to have insurance. So they're more at risk of losing everything."

The study found places in every state where people are at risk of flooding and probably don't know it, Fargione said.

Over the past 30 years, freshwater flooding in the United States has caused an average of $8.2 billion in damages annually, according to the study.

Knowing the places most likely to flood could help people avoid building in those areas, Fargione said. Without a full understanding of the risk, an additional 20 million people could be living in flood plains by 2050, he said.

It's also possible that climate change could exacerbate the flooding problem, Fargione said.

"We know that warmer air carries more water, and we expect bigger storms and storms in places that previously hadn't had storms of that magnitude," he said. "So we know there will be more flooding in places where people weren't expecting it."

The study was published in the journal Environmental Research Letters.