A new study finds that the maximum water levels in New York harbor during storms have raised about two and a half feet since the mid-1800's. This makes the chances of storm surge overtaking the Manhattan seawall over twenty times greater than they it was 170 years ago.

Though the rise in sea level is a global occurrence, it is only responsible for a foot and a half of the raised water levels in New York harbor since the mid-19th century. However, this new study shows that the city's "once in 10 years" storm tide has grown an additional foot in the same period of time. This storm tide increase means that New York City is at risk for more frequent and extensive flooding than was anticipated by the sea level raise alone.

manhattan sea wall

The lead author for this study is Stefan Talke, an assistant professor of civil and environmental engineering at Portland State University in Portland, Oregon who was accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union. The research published in this study confirms that the New York harbor storm tide produced by Hurricane Sandy was the largest since at very least 1821. Talke used tide gauge data that show a major "10-year" storm hitting New York City today causing bigger storm tides and potentially more damage than an identical storm in the mid-1800's. These "10-year" storms are called such because New York anticipates that a truly bad storm will hit the city every ten years. However, Talke suggests that there is a ten percent chance of any storm tide from a storm reaching the maximum height of six and a half feet, where as the maximum height in the 1800's was only five and a half feet.

"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," Talke said.