New York City is vulnerable to rising seas and larger, more powerful storms that result in more frequent and intense flooding and what was once a 500-year flood prior to human-induced climate change now occurs on average once every 24 years. This is according to a study published in the Proceedings of the National Academy of Sciences.
“Flood heights are increasing and have increased since the pre-anthropogenic era, not only because of rising sea levels but also because of the impact that climate change is having on tropical cyclones,” said lead author Andra Reed of Penn State University.
Reed and colleagues made their conclusions based on climate models that simulated tropical storms and subsequent flooding for the region beginning in 850. They found that average flood height increased by more than 4 feet from 850 to 2005.
When Hurricane Sandy hit New York in 2012, it caused an estimated $50 billion in damage and destroyed at least 650,000 houses. Prior to 1800, such a flood could be expected to hit the city every 3,000 years. Today, a flood of that magnitude will occur on average every 130 years, Reed said. 
“Our planning is not designed to look forward,” said Melanie Gall, a University of South Carolina professor who studies disaster risk and emergency management. “When you look at flood insurance or how flood zones are mapped, it is always based on past events. It never looks at how storm surge will change in the future. There needs to be more proactive planning.”
Continuing development in New York and other coastal areas is also making the impact of such floods worse, similar to how water in a bathtub rises when displaced by a person entering the tub.
“The area that will be affected is larger because there is more development,” Gall said.
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