Nearly four million Americans are at risk of severe flooding by the end of the century as climate change raises sea levels around the country.
Researchers from Climate Central and the University of Arizona say around 32,000 square kilometers of US land lies within one vertical meter of the high tide line - encompassing 2.1 million housing units and nearly four million people.
The team created a new model to identify the areas at risk of flooding. And with sea levels predicted to rise by at least a meterby the end of the century, they say that the government's currently designated flood zones are too small.
And a second study bears this out, showing that most of the 55 locations studied will see far more frequent storm-driven high water levels by the middle of the century.
At a state level, say the researchers, areas surrounding the Gulf appear to be the most vulnerable. In terms of population, Florida is most at risk, closely followed by Louisiana, California, New York and New Jersey.
Greater Los Angeles is of particular concern, they say, as previous research suggests that flooding may reach rare heights more swiftly in southern California than in any other mainland US area.
The second study examined the effect of heavy storms on past water levels at 55 stations across the US and combined these with estimates of future global sea level rises to predict the frequency and extent of future flooding.
"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," says Ben Strauss, a researcher at Climate Central.
"Sea level rise makes every single coastal storm flood higher. With so many communities concentrated on US coasts, the odds for major damage get bigger every year."