A new study has suggested that occurrence rates of New York City flooding during a storm will be much greater than what was previously thought. Maximum levels up to which water has risen in the New York Harbor during storms are nearly two-and-a-half feet since the mid-1800s.

This clearly indicates that water has chances to rise at the Manhattan seawall at least 20 times greater than what they overtopped 170 years ago.

Global sea level rise cannot be singled out for this cause as it accounts for less than foot and half. An additional foot of rise has been, surprisingly, sought by a once-in-ten-years storm for its maximum height since the mid-19th century.

"Knowing that there has been an increase in storm tides and figuring out why the increase occurred could help scientists better predict what will happen in the coming decades and help cities mitigate future problems", said Stefan Talke, the lead author of the new study and a professor in the civil and environmental engineering department of Portland State University.

Historic sea-level rise has undoubtedly increased the chances of flooding in New York Harbor and climate change will only exacerbate the situation, said Daniel Zarrilli, director of the newly launched Office of Recovery and Resiliency for New York City Mayor Bill de Blasio

Zarrilli said the administration understands the gravity of the situation and is being involved in taking steps to reduce the risk and build a stronger, more resilient New York. He talked about a report that showed a progress update on efforts to protect the city's 520 miles (840 kilometers) of coastline. Former Mayor Michael Bloomberg started these efforts for which the report was released by Mayor de Blasio on April 22.

Adding sand to beaches, reforming flood insurance are some of the efforts to ensure small relief for New York residents from floods, along with strengthening building codes in low-lying areas, and rebuilding areas damaged by Hurricane Sandy in October 2012.