Study reveals America's most flood-vulnerable communities

By Cheryl Dybas and Alison Satake

Inland flood zones often overlooked, leading to need for more risk awareness.

Flooding is not only the most common natural disaster -- it's the natural disaster that kills the greatest number of people.

As the threat of floods increases worldwide, scientists have been gathering valuable information on vulnerability to floods in counties throughout the U.S.

The results are published in the journal Annals of the American Association of Geographers.

Trends from 2001 to 2011 show that urban development has declined in coastal flood zones; however, development in flood zones in inland counties has grown.

"We found more urban development in inland flood zones than in coastal areas between 2000 and 2011, which is a worrisome trend," said scientist Nina Lam of Louisiana State University, a co-author of the study. "The implications are that people living in the coastal zone want to migrate inland. But they don't realize they are still vulnerable if they live in flood zones in inland areas."

The trend may point to a need for more awareness, education and communication about flood risk in inland counties, the researchers said. They believe that more affordable housing in non-flood zones and strategies to mitigate floods are also needed.

"These results show that people in coastal areas are more aware of flood threats than those living in inland flood zones, and that populations in inland areas are increasing," said Judy Skog, a director of the National Science Foundation's (NSF) Coastal SEES (Science, Engineering and Education for Sustainability) program, which funded the research. "This information could aid future flood-planning efforts in inland communities."

The researchers compiled urban development, flood hazard and census data and overlaid it on a map of the U.S.

Although the analysis shows that Americans have become more aware of the risk of floods over the 10-year study period, the researchers identified several U.S. hotspots where urban development has grown in flood zones, including those near New York City and Miami.

"Flooding is the most common and widespread disaster we face nationally, and the one that is the easiest to alleviate by effective planning," said Richard Yuretich, a director of NSF's Dynamics of Coupled Natural and Human Systems program, which co-funded the research. "This study provides important data on flood hazards across the country, and demonstrates that research and education about floods over the past decade have helped manage risk. Yet there are still places where people are in harm's way."

The three counties in the U.S. with the largest concentration of people living in flood zones are near the Gulf of Mexico: Cameron Parish in Louisiana, with 93.6 percent of its population in the flood zone; Monroe County in Florida, with 91.4 percent of its population in the flood zone; and Galveston County in Texas, with 82.8 percent of its population in the flood zone.

The research focused on the U.S., but scientists see the potential for the results to help address a worldwide threat. "This nationwide study of flood zones, human populations and urban development provides a tool that could be used globally," Skog said.