Rising sea levels threaten millions, reports find

Wednesday , March 14, 2012 - 5:06 PM

Tony Barboza

About 3.7 million people in the United States live within several feet of the high-tide line and are at increasing risk of coastal flooding as sea levels rise because of global warming, according to new reports.

Two studies published Wednesday paint a picture of the growing threat of the rising sea in combination with high tides and storm surges, offering grim predictions for California and other coastal states where scientists say that in coming decades, floods will hit more often and in places they never have before.

While Florida has the greatest number of people at risk, researchers found vulnerable populations on every coast, with Louisiana, California, New York and New Jersey following close behind.

In one study, researchers used new figures from the 2010 census and more detailed data on coastal elevation to map more than 12,000 square miles of low-lying coastline vulnerable to flooding with a predicted sea level rise of 1 meter by the end of the century.

"Our estimates of people or areas at risk have increased, which is troubling," said co-author Jeremy Weiss, a geosciences researcher at the University of Arizona. "The situation has the potential to be worse than what we were anticipating just a year ago."

The research was published Wednesday by Climate Central, a New Jersey-based research nonprofit that seeks to educate people about climate change, in collaboration with the University of Arizona and the National Oceanic and Atmospheric Administration.

A website produced to accompany the research, called Surging Seas, features interactive maps that can zoom in to the neighborhood level, illustrating where flooding might occur.

One of the studies used readings from dozens of tidal gauges across the country to predict that the swelling ocean, in combination with high tides and storm surges, will increase flooding in coastal areas over the next few decades.



The odds of floods are going up the fastest in Southern California, where scientists say storm surges that used to hit just once a century could by an annual occurrence by 2050.

That means densely populated coastal communities that for now are safe from high water -- particularly low-lying areas around Orange County, San Diego and the L.A.-Long Beach port complex -- would flood during coastal storms for the first time as the water line goes up over the next several decades.

"A lot of people and a lot of businesses have been built there. It's attractive to be near the water on flat land," said Ben Strauss, a co-author of the two studies and director of Climate Central's sea-level rise program. "Historically that land has been safe from flooding. But that's going to change."

Globally, sea levels have risen about 8 inches over the last century. The pace is expected to accelerate with climate change.

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