NYC Storm Tides Rise, May Lead to Extensive Flooding

A new study confirms that the odds of storm tides overflowing the Manhattan seawall have risen 20-fold from 170 years ago, and the Big Apple should brace for serious flooding in the future.

Maximum water levels in New York harbor during major storms have risen by nearly two and a half feet since the mid-1800s, in part due to rising sea levels, which have jumped nearly a foot and a half in the harbor.

Combining the newly calculated rise in storm tide with the surge in sea level, researchers found that today, waters can be expected to overtop the lower Manhattan seawall - 1.75 meters (5.74 feet) high - once every four to five years. Storm tides - or the amount that water levels rise during a storm - are supposed to crest over the seawall only once every 100 to 400 years, researchers report.

"What we are finding is that the 10-year storm tide of your great-, great-grandparents is not the same as the 10-year storm tide of today," lead author Stefan Talke said in a news release.

Tide gauge data analyzed in the study show that a major, "10-year" storm hitting New York City (NYC) today causes bigger storm tides and potentially more damage than the identical storm would have years ago. There is a 10 percent chance that storm tides, at any time, will reach their maximum height.

Researchers reached their analysis by photographing handwritten tide measurements which are kept by the US National Archives. The study's findings, published in the journal Geophysical Research Letters, indicate that storm surges may continue to get stronger and larger.

The study also added that Hurricane Sandy was the largest storm to rock NYC harbor since the 1800s.

Talke and his team point out the obvious causes of rising storm tides - climbing sea levels and global warming - but if local factors are at play, like deepening shipping channels, they may be in luck.

"If it turns out to be a local reason, as has been suggested in some cases, there could be local solutions as well," Talke said. "In some cases, we may be able to turn back the clock on that a bit."