As tides rise, flood risk grows higher

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, 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,” says study co-author Jeremy L. Weiss of the University of Arizona. “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. The team’s complete findings are published online in the journal Environmental Research Letters. For example, the research indicates the famed canal region in Venice, California will be vulnerable to flooding, says Weiss, a senior research specialist in 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 says. 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. “I am quite surprised and troubled by how much worse our new analysis indicates sea level damages could be in this century,” says Jonathan T. Overpeck, co-director of the UA Institute of the Environment and 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 says, 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. Lead author Benjamin H. Strauss, of Climate Central, says: “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.” Remik Ziemlinski of Climate Central also contributed to the study.