How climate change is forcing cities to rebuild stormwater systems : Short Wave Deep below our city streets lie intricate networks of underground piping built to carry away excess rainfall run off. These stormwater systems mostly go unnoticed until heavy rains overwhelm them, causing streets to flood. Now, with rising rainfall averages in much of the nation, cities need to plan for more water. Guest host Dan Charles talks to climate correspondent Lauren Sommer about the challenges of such planning and why many cities aren't set up to handle the coming rains.

How climate change is forcing cities to rebuild stormwater systems

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EMILY KWONG, BYLINE: You're listening to SHORT WAVE...

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KWONG: ...From NPR.

DAN CHARLES, HOST:

Hello, SHORT WAVErs. Dan Charles here. Go stand on the corner of a city block. It's the usual scene - the road, sidewalk. Notice that storm drain on the corner? Well, NPR science correspondent Lauren Sommer is here to tell us there is a whole different way to think about all this stuff we've built.

LAUREN SOMMER, BYLINE: Hi, Dan. And yes, what you're seeing really is a moment frozen in time.

CHARLES: That sounds very profound, Lauren. What does it mean?

SOMMER: Really, it's the moment that all that concrete was poured. It was probably decades ago. That's when city planners designed what you're seeing. And they said, you know, all the stuff we're building has to withstand the elements, rain in particular because in a city, rain becomes runoff.

CHARLES: Right. With all that pavement, can't soak into the ground, so it just runs off.

SOMMER: Yeah. But luckily, there's this network of pipes under our feet that carries all the runoff away. It's the storm water system.

CHARLES: I love storm water systems, this incredible network of huge pipes underground that nobody knows exist.

SOMMER: Exactly, yeah. And city planners design them to handle the kinds of storms that particular city experiences, at least the kind that it used to experience.

CHARLES: Right - because storms are changing - right? - getting more intense as the climate gets hotter?

SOMMER: Yeah. And extreme storms in particular - they're dropping even more rain in most of the country. And that's overwhelming storm water systems built for last century's milder storms.

CHARLES: So you're saying our cities are designed for a climate that no longer exists. Those miles and miles of buried concrete pipes aren't ready for all the water that's coming.

SOMMER: Exactly. And cities know this is a problem. Flooding is getting worse. The good news is that soon, they're going to have billions of dollars to spend on improving their water systems from the federal infrastructure bill that Congress passed. But right now, cities don't have forecasts about how climate change will make rainfall even worse where they are. In fact, many of them are still building infrastructure based on really outdated rainfall records, the records of last century.

CHARLES: So today on the show, how cities are struggling to plan for climate change and the relatively simple fix they're asking for. You're listening to SHORT WAVE, the daily science podcast from NPR.

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CHARLES: So, Lauren, when I think of flooding, I usually think of creeks and rivers. You know, it rains a lot. They overtop their banks, flood homes or buildings next to them. But you're talking about something different?

SOMMER: Yeah. The flooding I'm talking about can happen far from any river, in places where people aren't really likely to expect it. It happened this winter where I live, actually.

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SOMMER: There was a big rainstorm in the San Francisco Bay area in December. It's what's known as an atmospheric river.

The gutters are full of water. It's pouring down the side of the street.

I was recording on my phone.

All the way down to a storm drain. And this storm drain is overloaded, and you've got a huge puddle gushing into the street here.

CHARLES: I see that all the time, actually, in a big rainstorm, Lauren. You got flooded intersections that make you nervous driving through them.

SOMMER: Yeah. I mean, sometimes, it's just that the storm drain is kind of clogged. But in a heavy downpour, it's because the system is overwhelmed. The size of the pipes underground can't handle all that water. And it can cause flooding that's more than, you know, just a nuisance. That happened last summer, when the remnants of Hurricane Ida hit the Northeast.

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PHIL MURPHY: So to state the obvious that yesterday, Tropical Storm Ida swept across the state with high winds...

SOMMER: That's New Jersey Governor Phil Murphy giving an update on the storm that ultimately caused 50 people to drown.

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MURPHY: The majority of these deaths were individuals who got caught in their vehicles by flooding and were overtaken by the water.

SOMMER: Other people died in their basement apartments. Another deadly storm was Hurricane Harvey, which hit Houston in 2017 and dropped 60 inches of rain.

CHARLES: But, Lauren, that was such a phenomenal amount of rain. Could any city's infrastructure handle that much?

SOMMER: No, probably not because to build a storm water system that's big enough to carry all of that away, it would be incredibly expensive. So cities just don't build them that large. But even weaker storms are still a problem. I mean, before Harvey hit, the city planners there knew that flooding was getting worse. And one of the reasons is that the city was using old rainfall records.

CHARLES: Old rainfall records. I want to make sure I understand this. You're saying flooding was getting worse even before Harvey because the city was designing its - you know, its drains and everything to handle the amount of rain it typically got in the past?

SOMMER: Right. Yeah. So cities design their stormwater infrastructure based on a particular kind of storm. You know, that's typically a 1-in-5-year storm or 1-in-25-year storm. Cities need to know how much rain those kinds of storms bring to their area. So they rely on historical rainfall records to show that average. And most cities get those records from a federal agency, the National Oceanic and Atmospheric Administration, or NOAA. That agency compiles all the rainfall data and puts out a report.

CHARLES: NOAA is actually my favorite acronym for a federal agency - I got to tell you that - that deals with flooding. But listen. Cities must know how much rain they're getting. Why do they need this data from NOAA?

SOMMER: Right. Cities get all kinds of rainstorms all the time. But what NOAA does is the agency looks at all that historical data, averages it together. And that helps cities understand what kinds of storms they should plan for. So what's a common storm look like? What's a rare storm look like? They really need...

CHARLES: OK.

SOMMER: ...Real numbers to plan with. But the problem with NOAA's reports is that they're old.

CHARLES: Oh. How old?

SOMMER: Well, some Texas agencies were using reports that were last updated in 1961. Houston had compiled its own data, but it was still 20 years old.

CHARLES: See, I don't understand. Rainfall data is being collected all the time at weather Stations. Why would these reports be so outdated?

SOMMER: Yeah. It has to do with NOAA's policies. Under the current system, the agency only updates these rainfall reports when a state or local agency requests and pays for it themselves, which can be expensive. So in Texas, you know, agencies and flood districts had to raise $1.75 million to get new reports for the whole state. They did that in 2016 because they knew they needed to. It seemed like the storms were changing.

CHARLES: So they wanted this new, updated information on rainfall. They got it. What did it say?

SOMMER: Well, here's how Craig Maske, chief planning officer at the Harris County Flood Control District, describes it.

CRAIG MASKE: May have been a case of be careful what you wish for because, especially those of us in the Houston and Austin areas especially, saw pretty large increases in the rainfall.

SOMMER: So just one example - the one-in-100-year storm used to drop 13 inches of rain, but now it drops 17 inches of rain.

CHARLES: Seventeen inches instead of 13 - that's a lot more water to plan for. But does that matter? What exactly does that mean for Houston?

SOMMER: It changes a lot. It means all the roads, bridges, housing developments they were planning to build, all those big projects need to be engineered to handle more water, and that raises the costs. The Regional Transportation Planning Agency for Houston told me that it made the big projects that were planned there more expensive, you know, $150 million to $200 million more expensive. That's a tough change to make. But Maske told me because the city had just been through this record-breaking disaster, many people saw the need to spend that kind of money.

CHARLES: So the updated rain data shows storms have gotten worse. But I'm thinking the climate's still warming, rain patterns will keep changing. So you don't have to just build stuff for today's climate. You want to actually get ready for the future.

SOMMER: Yeah. And that's the other huge issue here. There are plenty of nationwide studies, you know, about how big storms are going to keep getting more intense. In New Jersey, for example, by the year 2100, extreme storms can release up to 50% more rain. But cities need localized data to show how that's going to happen to them specifically.

CHARLES: 2100 feels far away, but I guess if you're planning a city, you really have to think that far ahead.

SOMMER: Right. It all lasts a long time because it's supposed to. That's what Chad Berginnis, executive director of the Association of State Floodplain Managers, told me.

CHAD BERGINNIS: When you put a bridge in today, that bridge is going to be designed to last maybe 25, 50, 75 years. And so we really need to know or get an estimate of what that future condition is if we're going to design it properly.

SOMMER: There are a handful of cities that are working to get tailor-made climate forecasts by working with universities.

CHARLES: What do they do, call up local professors and ask them to do a report?

SOMMER: I mean, yeah. They kind of form some partnerships. San Francisco is working with Lawrence Berkeley National Lab. Seattle and Portland work with the University of Washington. In fact, Seattle upgraded a huge stormwater project based on the climate change information they got; they made it able to handle even more water. But you can see how this might be problematic - right? - because those are big cities with big universities.

CHARLES: Sure.

SOMMER: Smaller cities, more rural areas, they don't have connections like that, so they're not going to get that information about climate change.

CHARLES: So what's NOAA saying about this? Are they open to changing the way things are done to help cities?

SOMMER: They are. I spoke to NOAA officials who say the way they're doing things right now is not ideal. This kind of patchwork approach to the rainfall records, which are - they're called Atlas 14, it's a problem, they agree. In fact, it would be more efficient and cheaper to do this whole analysis for the whole country at once because it's expensive to break it into these small regional studies. But until now, NOAA's had no budget for this nationwide approach, even though Chad Berginnis of the Association of State Floodplain Managers says it really wouldn't cost that much.

BERGINNIS: The cost to do this is almost decimal dust when it comes to the overall federal budget. We're only talking probably about $3 million to $5 million a year to produce these data.

CHARLES: Three to five millions dollars - I mean, you can spend more than that these days building a pedestrian bridge. Shouldn't NOAA be able to find that much money?

SOMMER: It's possible it could happen soon because NOAA is going to be getting a lot of money from the Federal Infrastructure Bill 2. You know, right now, the agency is coming up with a spending plan for that, and they told me they can't comment at this time about whether rainfall records or climate change forecasts will be part of it, but a lot of city planning officials are really pushing for it.

CHARLES: It seems like this story is really about sort of the nitty-gritty details of dealing with the practical effect of climate change. Cities know it's an issue they need to plan for, but actually doing it is quite challenging.

SOMMER: Yeah. And this is something I keep coming back to as a reporter over and over because the science is clear at the larger scale, but that science kind of has to trickle all the way down into those, you know, few sentences about stormwater drainage in, like, a city's planning ordinances.

CHARLES: Yeah.

SOMMER: And each city is doing this on its own. It's not easy, and stormwater is, you know, out of sight, out of mind until a big storm hits. You know, kind of on top of this whole thing is most cities already have a huge backlog of maintenance projects to do, and now they're facing some very expensive upgrades to deal with climate change. You know, but it's a problem that's going to get worse the longer they wait.

CHARLES: Well, thank you very much for digging this up, Lauren.

SOMMER: Of course. Happy to.

CHARLES: This episode was produced by Berly McCoy, edited by Stephanie O'Neill and fact-checked by Kathryn Sypher. The audio engineer for this episode was Patrick Murray. I'm Dan Charles. Thanks for listening to SHORT WAVE from NPR.

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