Short Wave - Climate Change Means More Subway Floods; How Cities Are Adapting

Episode Date: September 15, 2021

Millions of people rely on subways for transportation. But as the world warms, climate-driven flooding in subways is becoming more and more common. NPR correspondents Lauren Sommer and Rebecca Hersher talk about how cities across the world are adapting. For more of Rebecca's reporting on climate-driven flooding, check out "NYC's Subway Flooding Isn't A Fluke. It's The Reality For Cities In A Warming World."(https://www.npr.org/2021/09/02/1021185475/climate-change-means-more-subway-flooding-worldwide-like-new-york-just-experienc)You can follow Lauren on Twitter @lesommer and Rebecca @rhersher. Email Short Wave at [e-mail] pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. A flash flooding siege in the northeast. Flooding killed at least 50 people in the New York region a couple weeks ago. The floods were caused by the storm previously known as Hurricane Ida. That storm got powerful when it formed over abnormally warm water in the Gulf of Mexico. And when the hurricane hit Louisiana, it had powerful winds. But by the time it got to New York, New York, it was all about the rain.

For the first time in recorded history, the National Weather Service issuing a flash flood emergency for all five boroughs of New York City. More than seven inches of rain in just a few hours. Waterfalls pouring down station stairs, trains pulling into fine platforms submerged. People waiting through waste high water. The night of the storm, the mayor of New York told residents to avoid the subways in a city where millions of people rely on them. Climate change means more flooding in subways.

And New York is just the latest. It's happening all around the world. And that means cities are racing to keep the water out. I'm Rebecca Hersher, a climate reporter at NPR. And I'm Lauren Summer, also a climate reporter at NPR. Today on the show, subways provide crucial transportation for millions of people and they're magnets for climate-driven flooding. We're going to talk about how cities are adapting.

You're listening to Shortwave, the Daily Science Podcasts from NPR. Okay, Rebecca, we're talking about flooding in subways. There was a lot of footage of New York subway, and it seemed like an incredible amount of water was pouring into it. Yeah, and that was flooding from torrential rain, which is getting more common as the earth gets hotter. So what happens is a lot of rain falls in a very short period of time. New York got more than three inches in an hour at one point during the storm. Wow. And there's nowhere for the water to go.

It's a big deal. One expert I talked to estimated that dozens of cities have already experienced flooding in their subways and that hundreds of thousands of passengers have been directly affected. So that means they've experienced water firsthand in a subway. But there's another kind of flooding too, salty flooding. Salty flooding. It sounds like kind of extra nasty flooding, but I'm pretty sure you just mean saltwater here, right? Yeah, exactly. Salty flooding, not a technical term. It's a turn. I made up, is flooding related to sea level rise, which is also happening because of climate change. So salty water is getting into stations, into tunnels. It can happen slowly and repeatedly, like in some parts of Boston, the subway system, you know, there's flooding during high tides. Or it can be dramatic, like during Hurricane Sandy in New York City, the storm surge was huge and it flooded multiple tunnels. Okay, so two different kinds of subway flooding, you know, both are

tied to climate change. I have to say this feels like kind of an insurmountable problem because water flows downhill. I know that. I'm a science reporter. Good job. And subways are underground. Is there anything cities can do about it? Yeah, it is a thorny problem, but there are actually lots of things that can be done to keep water under control. And they all start with predicting where and when these floods will happen because it's not every station, every tunnel, every time it rains, right? In fact, it can be pretty hard to predict where the flooding hotspots will be in a city. Huh. Wait, why is that? It seems like the flooding hotspots would be near the water, right? A good guess, but not always. So here's an example. You know, I live in Baltimore. That means I'm right up the road from a subway system that has repeatedly flooded. That's the subway system in Washington, D.C.

So here we are on Connecticut Avenue. It's one of the thoroughfares of the city. So I met up with Nicholas Bernard outside a subway station. He works for the D.C. Department of Energy and the Environment. And this station that we met up at is in a residential area. It's next to a shopping center. There's CVS. There's restaurants. There's banks. There is no water in sight.

We're miles from any major river, but there is a slight hill in each direction. It is very subtle. So if you imagine a drop of rain falling on a street, which way does it go? And it starts to go downhill. And so a drop of rain that goes a block. north that starts to come here in a drop of wind that goes a block south that starts to come here too. Okay, so I'm imagining you've got torrential rain and all those rain drops, they run downhill towards the subway station from every direction. So there's just so much water. It overwhelms the drainage

pipes. You've got water pooling on the streets. You've got puddles on the sidewalk. And then it just goes wherever it can, basically. Exactly. You painted a picture. And that water goes into air vents. It goes downstairs, it goes down the escalator for the subway station. And if I'm at the bottom of the stairs, what do I see? What you would see is you would see a waterfall coming down the stairs. And that actually happened at this station in 2016. There was a waterfall on the escalator. Now, even on a sunny day, there are sandbags outside the station entrance,

and they're ready to be stacked up if there's a rainstorm to prevent that from happening again. Okay, but a short-term fix, I'm guessing. Yeah. Yeah, sandbags are not the whole answer. And the bigger fixes are more expensive and more time-consuming. So Bernard's office is working on a computer model that would help predict where this type of flooding is most likely to happen in the city. And the transit authority is spending millions of dollars waterproofing leaky tunnels, keeping water out of vents and station entrances, upgrading emergency warnings so that people know when this is happening. Wow, yeah.

I mean, is this something every city with an underground transit system is going to have? have to do? They're going to have to try to predict where the floods will happen and how to stop them. Yeah. In fact, some of the cities that are on the cutting edge of this are in Asia, and that's for a couple of reasons. So climate-driven flooding is really serious in many Asian cities with large subway systems. Think Taipei, Bangkok, multiple cities in China and Japan. And like the U.S., this is part of the world where there are tropical storms. They can bring both heavy rain and salty flooding from storm surge. But unlike the U.S. and Europe, the subway systems there are often quite new, which means they were designed for a more modern climate using more modern construction techniques.

So you can imagine it would be easier to waterproof subway tunnels that originally opened in the 1990s, like in Taipei, compared to tunnels built in the early 1900s, like New York. Yeah, I could see that. So what are the lessons that the U.S. should be taking from these other countries? So, for example, Taiwanese authorities, they raise. the entrances to stations to keep the water out. Wait, so the entrance is higher than the street level? Like you actually have to walk up before you go down? Yeah, exactly. Another example is Bangkok. They've long had a flood warning system to keep passengers safe, even though the city has struggled to prevent underground train flooding. In Kyoto, Japan, researchers actually built a full-scale model

of a subway station escalator and simulated a flash flood to see how much water people could safely walk through. Oh, wow. Okay. Yeah. That's wild. Yeah. And, you know, that model helped authorities create emergency plans for closing stations during storms so people wouldn't end up in a dangerous situation underground. Huh. So it seems like with all of these examples, it's expensive. It's got to be pretty expensive to keep water out of subways. And the stakes are high, right? Because this is a real safety issue. People actually drown, right? If there's a flash flood underground? Yeah. Yeah, totally. And this is, something I heard about from some of the experts I talked to. Preparing for and preventing subway flooding and public transit flooding in general, it's really labor intensive and it is really expensive.

So an official for the Washington D.C. Transit Authority told me they are spending more than they ever have keeping water under control. Millions of dollars. And there may be more money coming from the federal government. You know, the infrastructure bill that's in Congress includes upwards of $100 billion for trains. It also strikes me that there's a real kind of climate-y tension here. You know, on one hand, climate change is making it harder to run these kind of reliable subway systems. On the other hand, you know, subways are exactly the kind of public transportation that helps control emissions, right, to avoid more climate change. Yeah, isn't that like a thorny and comfortable thing? And that's actually why even though it's so clear that subways are prone to climate-driven flooding, they're still

popular. Like, Fort Lauderdale, Florida is considering a new subway line right now. Okay. A city known for water. It's right on the coast. Yes. Also a fun fact, Fort Lauderdale is sometimes called the Venice of America. So that gives you a sense of exactly how watery it is. But it also has a traffic problem. And the mayor told me he's excited about the possibility of less traffic, fewer passenger cars downtown, if they build this new underground train. And he's confident that it won't flood. Although, Experts I spoke to said it's important to think long-term before building underground infrastructure in places like Florida, where sea levels are rising really quickly. Yes, that long-term thinking, I can see how that would raise some eyebrows. Yes.

Becky, thank you for this reporting. My pleasure. Stay dry. This episode was produced by Rebecca Ramirez and Thomas Liu, edited by Viet Leigh and fact-checked by Indy Kara. I'm Lauren Summer. I'm Rebecca Hersher. You're listening to Shortwave from NPR.