Rising Seas Put Millions of Americans at Risk for Flooding

New estimates suggest more U.S. land prone to flooding than previously thought.

About 3.7 million Americans are at risk for flooding as the sea level continues to rise in the coming century, according to a new study from a team that includes University of Arizona researchers.

Areas on the south Atlantic Seaboard and surrounding the Gulf of Mexico appear to be most prone to future flooding. In terms of numbers of people at risk, Florida is the most vulnerable, closely followed by Louisiana, California, New York and New Jersey.

“We found that 3.7 million people live within 3 vertical feet of the present-day high tide line,” said study co-author Jeremy L. Weiss of the UA. “It’s not only beach-front property at risk, but low-lying areas further inland, as well.”

The researchers and other scientists anticipate the sea level will rise about 3 feet by the end of the century. In the U.S., coastal regions within 3 vertical feet (1 meter) of the high-tide line are most at risk – an area that totals about 12,350 square miles (32,000 square km) – larger than the state of Maryland.

The rising seas also will affect the nation’s seaports. The top nine U.S. ports, ranked by tonnage, include ports on the East Coast, the Gulf of Mexico and also California’s ports of Los Angeles and Long Beach.

Other areas at risk in Southern California include beaches, marinas and housing along the coast.

For example, the research indicates the famed canal region in Venice, Calif. will be vulnerable to flooding, said Weiss, a senior research specialist in the UA’s department of geosciences.

“Where I visit at Mission Beach in San Diego, 1 meter of sea level rise will put the whole beach area at risk of being under water, right up to the boardwalk and houses that line the sand,” he said.

Benjamin H. Strauss of Climate Central is the lead author on the study, Tidally adjusted estimates of topographic vulnerability to sea level rise and flooding for the contiguous United States.” Other authors are Remik Ziemlinski of Climate Central and Jeremy L. Weiss and Jonathan T. Overpeck of the UA.

The paper was published online today in IOP Publishing’s journal Environmental Research Letters.

The research expands upon the team’s previous work by using the most recent (2010) census figures, more detailed data on coastal elevation and linking the coastal elevation to local high-tide levels.

When the researchers entered the newer, more detailed information into their computer models, they found that more land area was at risk from sea level rise than their previous work indicated.

Overpeck said, “I am quite surprised and troubled by how much worse our new analysis indicates sea level damages could be in this century.”

Overpeck is co-director of the UA Institute of the Environment and a UA professor of geosciences and of atmospheric sciences.

Human-caused climate change is causing global sea levels to rise from thermal expansion – the expanding of water as it warms – and the melting of glaciers and ice caps.

In addition, Weiss said, global warming is driving additional changes to the great polar ice sheets that result in more ice being discharged from land into the ocean, raising sea levels even more.

Strauss said: “The sea level rise taking place right now is quickly making extreme coastal floods more common, increasing risk for millions of people where they live and work. Sea level rise makes every single coastal storm flood higher.

“With so many communities concentrated on U.S. coasts, the odds for major damage get bigger every year.”

– By Mari N. Jensen

*Source: The University of Arizona (Published on March 14, 2012)

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