Environment

Experts: Long Island could see ‘very strong increase’ of flooding in two decades

A new study has predicted more frequent high tide flooding on U.S. coastlines in the mid-2030s, exacerbated by climate change-induced sea-level rise and tidal patterns influenced by the moon’s 18.6-year cycle. 

Based on this study, Stony Brook University professor Edmund Chang said Long Island could see “a very strong increase” in flooding in the early 2040s. 

Led by members of the NASA Sea Level Change Team from the University of Hawaii, the July 2021 paper predicts increased flooding for coastal communities, heightened in part by the moon’s “wobble” — a regular oscillation that suppresses daily tides during half of the moon’s cycle and amplifies them during the other half. 

Mr. Chang, interpreting supplementary data, said the region is on a timeline similar to Boston, the nearest city discussed in the paper. The study projects a minor increase in flooding for the Long Island region in the late 2020s and then a period of relative stability until the early 2040s. 

“I think this has an important message to both citizens as well as management, that actually we have to be aware of this and don’t get complacent when we don’t see flooding events increase, especially over the next few years,” said Mr. Chang, whose research focuses on mid-latitudinal storms, including their societal impacts and how they may be influenced by climate change. “The more major change for our region is actually predicted to be early 2040s.” 

Flooding is already a concern for Long Islanders. Storms such as Superstorm Sandy and hurricanes can do serious damage to the region. As of May 2019, New York State was implementing 29 projects in Suffolk County to repair and bolster communities against future storms, according to the governor’s office of storm recovery. 

“It’s pretty well understood at this point we’ve seen some amount of a sea level rise globally, which is already starting to impact … what we call ‘sunny day flooding,’ ” said Kevin Reed, a Stony Brook University professor who studies climate modeling and extreme weather events. “These are events in which the coastline or your downtown urban area, in areas sometimes like Miami, it’s flooding on a sunny day. This is coming from sea level rise.” He added that “it’s worth noting” sea level rise expectations are not uniform; the ocean will not rise at the same levels everywhere, although many coastal regions are going to be susceptible to flooding. 

“I think where the real impacts will come from, particularly for our region — you know, the sunny day events will happen, particularly in urban areas — but the real impacts are going to come from when we have storms associated on top of that sea level rise,” Mr. Reed said. 

For instance, if Long Island is hit with a tropical storm, storm surge combined with high tide and sea level rise could wreak havoc on island structures and infrastructure. Flooding from significant rainfall on top of all that could “make things even more devastating,” according to Mr. Reed. Part of the reason Superstorm Sandy caused such extensive flooding across the island and in the New York metro area nearly a decade ago is that it occurred at a full moon during high tide. 

“Another aspect of [increased flooding] is actually the fact that storms themselves could be changing. A storm is maybe going to be more intense in 2030, which means it could have a larger storm surge associated with it,” Mr. Reed said. 

That compounded effect of sea level rise, potential increases in storm surge and increases in the amount of rain falling during individual events, he said, could make these events “become really impactful.” 

“It’s really through these types of flooding events, and the changes in our weather and our extreme weather events, that we as Long Islanders will really feel the impact of climate change,” he added. 

Mr. Chang said the study’s results are not certain — flooding over the next few years will be impacted by the rate of sea level rise. The NASA paper is mostly using intermediate sea level rise projections from NOAA, which projects an increase of about 3.2 feet by the end of the 21st century. 

“If sea level increases faster, then that timeline may change,” he said. “If sea level increases slower, then it will be later.” 

Mr. Chang added that “we need to plan ahead” for future flooding. Although total rainfall “may not change a lot,” it will be “more concentrated into shorter periods of time,” creating more intense rainstorms. 

“In terms of infrastructure, the drainage system that was designed for a decade or a couple of decades ago will not be as effective as time goes on, because we expect more water to come down within the same period of time,” he said.

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