500-year floods about every 4 years? That could be Jamaica Bay's future, study says

If the world continues on its current path, Jamaica Bay could face devastating flooding about every four years in the future.

Reza Marsooli and co-author Ning Lin found that under a very high greenhouse gas emissions scenario, rare flood levels will become much more common in the bay during hurricanes. Marsooli says a "very alarming conclusion was that a 500-year flood level in Jamaica Bay will become a 4-year flood level by the end of the 21st century."

That means that the kind of flooding previously seen on average every 500 years, like in Superstorm Sandy, will happen every four years or so instead. Sandy cost New York City $19 billion in damage and lost economic activity, according to the city, and had a devastating impact on Long Island's South Shore.

Their paper was published in November in Climatic Change. Marsooli is an assistant professor at Stevens Institute of Technology in New Jersey whose research is mainly focused on flood hazards, flood mitigation and climate change impacts. He said Inwood and the east side of Jamaica Bay, east of Kennedy Airport, are very vulnerable to sea level rise.

This interview has been edited and condensed. It discusses a representative concentration pathway, called RCP8.5, which is a high greenhouse gas emissions scenario. Professor Katharine Hayhoe, who codirects the Texas Tech University Climate Center, said in an email that "we are still on an RCP8.5 pathway." But she said she very much hopes "that we will be bending away from it very soon" — and that "based on countries' commitments to the Paris Agreement there is some basis for that hope."

NEWSDAY: Can you walk me through the main findings of your study on Jamaica Bay?

MARSOOLI: We looked at hurricane flood hazards in the Jamaica Bay area in Brooklyn and the Queens area in the Jamaica Bay watershed. The purpose was to look at the combined effects of sea level rise and storm climatology change on flood hazards in Jamaica Bay. Our method was based on numerical modeling, so we used dynamic models to simulate a large number of hurricane scenarios.

What we found was interesting and very alarming, actually. This study was based on the worst-case climate change scenario. I mean a very high greenhouse gas emissions scenario. It means there won't be any climate mitigation.

NEWSDAY: That's the RCP8.5 scenario, right?

MARSOOLI: Exactly. Using the results of our models, we concluded that based on this high greenhouse emissions scenario, in Jamaica Bay a current 100-year flood level [for the period 1980-2000] will be a 9-year flood level in 2050, and a 1-year flood level in the late 21st century. It means that if a flood level at this time in Jamaica Bay has occurred on average every 100 years, that flood level is going to occur on average every year in the late 21st century.

The main cause of this abrupt change is sea level rise. We found that not only in Jamaica Bay, but in the Northeast of the United States, sea level rise is the main cause of increase in future flood levels. Hurricane climatology change also will contribute, but not as much as sea level rise. The climatology of future hurricanes is going to change because of global warming — but the impact on flood levels in the Northeast is not as much as the impact of sea level rise.

Another very alarming conclusion was that a 500-year flood level in Jamaica Bay will become a 4-year flood level by the end of the 21st century. It means that if we see a flood level which occurs on average every 500 years, like Hurricane Sandy, then we'll see that flood level every four years on average by the end of the 21st century.

NEWSDAY: To linger on Superstorm Sandy, it was such a disaster for New York City and New Jersey and Long Island, so it's just hard to imagine that happening every four years by the end of the century. But that's what people have to think about, right?

MARSOOLI: Exactly. Under this high greenhouse gas emissions scenario, we can see, with 50% chance, the sea level rise is going to be more than 1 meter or 3 feet. Because of that large increase in the mean sea level, in the future we are going to see a much higher flood level during a storm, because the mean sea level is going to be higher, and if you add a little bit of storm surge on top of that, you are going to get a flood level which would be almost equal to Hurricane Sandy flood level. But again, this is a very pessimistic projection, because we are looking at RCP8.5, and I'm hoping that all nations, including the U.S., are going to take action against climate change, and we're going to mitigate the impact of climate change. If there won't be any action, then these nightmares will happen, actually, by the end of the 21st century.