A new study shows that within three decades, floods that used to strike New York City only once every 500 years, could occur every five years.

The study was published Monday in the Proceedings of the National Academy of Sciences, just days ahead of the fifth anniversary of Superstorm Sandy.

Researchers based their analysis on models that factored in predictions for sea level rise and storm intensity.

They say before 1800, floods of 7.4 feet or more struck the city once every 500 years.

Floods like that now occur every 25 years.

They could happen once every five years between 2030 and 2045.

The research team included scientists from Rutgers University, Penn State, MIT, Princeton, Nanyang Technological University, the University of Massachusetts and the Woods Hole Oceanographic Institution.