The front yard of a vacant home is flooded from rising ground water in Robbins, Maryland. Many homes in the region are slowly eroding away as sea levels rise — a problem set to get worse, according to a new study. (Mark Wilson/Getty Images)

Coastal flooding from sea-level rise and human activity could increase “several hundredfold” by 2100, researchers say this week in the journal Nature Climate Change.

This projected surge, then, could threaten U.S. cities from the Northeast to Texas, thanks to the impact of sea-level rise and the predicted increased frequency of large coastal storms taken together.

"When you look at hazards separately, it's bad enough, but when you consider the joint effects of two hazards together, you can get some surprises," said Radley Horton, a climate scientist at Columbia University's Earth Institute and a study coauthor, . "Sometimes, 1 plus 1 can equal 3."

Water temperatures, which influence sea level, are expected to rise sharply in the 21st century along the eastern United States. Redder areas on the map show projected temperatures at the higher end of the scale. (Little et al., Nature Climate Change 2015)

In the short term, flooding from this year's El Nino system could cause additional days of flooding across many U.S. coastal communities, with the worst impacts expected in the mid-Atlantic, the National Oceanic and Atmospheric Administration said earlier this month.

Glacier melt and the expansion of seawater as the ocean warms acts as the main drivers of sea-level rise around the world, both today and in the future. The U.S.'s East Coast might be in particular danger, as there, the sea is rising even faster than the 8-inch-since-1980 world average, . Current models predict an additional 2-to 4-foot increase by 2100; some models go as high as six feet, researchers said in the press release.

But the total threat to the coasts need to also consider the impact of severe storms, which is why the current paper analyzed both impacts for five locations: Atlantic City, New Jersey; Charleston, South Carolina; Key West, Florida; Pensacola, Florida, and Galveston, Texas. In these cities, with these two factors taken together, the flood level might increase 35 to 250 times. Additional glacier and ice sheet melt could only add to the hazard.

Recently, a study predicted that over the next several thousand years, the could add upwards of 160 feet to the world's oceans, a “sea-level rise unprecedented in human history.”

Both papers urged action toward greatly reducing global greenhouse gas emission. "By using more and more fossil energy, we increase the risk of triggering changes that we may not be able to stop or reverse in the future," co-author of the Antarctic study Anders Levermann said in a press release.

MORE ON WEATHER.COM: Stunning Photos of Climate Change's Impact

The Ash Creek Fire seen here is one of some 27,000 fires which have destroyed nearly 2 million acres of the western U.S. since the start of 2012. Extremely dry conditions, stiff winds, unusually warm weather, and trees killed by outbreaks of pine bark beetles have provided ideal conditions for the blazes. (Credit: NASA)