The staircase was filled to the brim with water despite the fact that it hadn’t rained that day. Most passing New Yorkers shrugged the unusual scene off and kept walking, but illustrator Kaye Blegvad decided to stop and snap a photograph of the G train’s flooded Broadway Station entrance.
“The other subway entrances were dry and normal and nobody seemed to be freaking out, so I just got on the train,” Blegvad tells Quartz’s Zoë Schlanger. “Only once I was on the train did I start thinking, wait, that really was quite insane.”
After accessing the platform through a drier station entrance, Blegvad posted the image on Twitter alongside the caption “MTA explain yourself.”
The Metropolitan Transit Authority Twitter account replied about 90 minutes later. The page offered up a joke—“We’re pivoting to submarines”—before revealing the actual explanation: “We were testing a new ‘flex gate,’ which is a flood barrier that would allow us to seal off a subway entrance. We ‘test flood’ the entrance for four hours to make sure it was installed correctly, which it was.”
The account added, “We're doing this because climate change is real.”
In 2012, Hurricane Sandy flooded a dozen New York City subway tunnels and nine train stations, inflicting billions of dollars of damage on the city’s transit system. At the time, subway staff only had sandbags and plywood to protect stations from incoming water.
“We've learned our lesson—won't happen again,” MTA Chairman Joe Lhota told NY1’s Jose Martinez in 2017.
But actually, we were testing a new "flex gate," which is a flood barrier that would allow us to seal off a subway entrance. We "test flood" the entrance for four hours to make sure it was installed correctly, which it was!— NYCT Subway (@NYCTSubway) November 20, 2019
We're doing this because climate change is real. ^JLP
The flex gate is one of several tools used to protect low-lying subway stations from a storm surge, or an abnormal rise in seawater triggered by strong storm winds that push ocean water ashore. The gate—developed by engineering company ILC Dover—is made of woven Kevlar and is designed to be deployed by a single person within minutes. As Justine Calma reports for the Verge, the MTA has already installed 65 flex gates around the city; the transit authority plans on installing an additional three gates in the near future.
“Our barriers are impervious and designed to handle flooding as much as 16 feet deep,” Dan Klopp, a product managing marketer at ILC Dover, tells Atlas Obscura’s Isaac Schultz. “There can be some slight leakage at the interfaces between our barriers and the surrounding infrastructure, however this amounts to much less water ingress than would happen during a light spring rain shower.”
Flex gates aren’t the only devices employed to keep a future storm surge out of the subway’s tunnels: According to the Verge, the MTA has also installed thousands of portable vent covers, as well as heavy, submarine-like doors. As Schultz reports, officials have even outfitted high-risk, low-elevation stations with “resilient tunnel plugs”—essentially 32-foot-long balloons.
A separate threat linked with hurricanes is groundwater seeping into the underground tunnels.
“These gates do not address the increasing stress of groundwater penetration into the subway, which is also likely to increase with climate change,” Thaddeus Pawlowski, managing director of Columbia University’s Center for Resilient Cities and Landscapes, tells Atlas Obscura. “Many of the streams that once flowed through the city are buried underground and find their way into the subway.”
In the event of a major hurricane, the MTA will deploy flood protections days before the actual storm reaches the city.
“We're always going to have a 24-hour period of time in the event that we know there's a hurricane coming,” Lhota told NY1 in 2017. “There's more than ample time.”