Climate change lessons from California's historic flooding : Short Wave Winter storms have flooded parts of California, broken levees and forced thousands to evacuate. Climate change is altering the historic weather patterns that infrastructure like reservoirs and waterways were built to accommodate. Urban planners and engineers are rethinking underlying assumptions baked into buildings and water systems in order to adapt to the changing climate. Today, NPR climate correspondent Lauren Sommer walks us through three innovations happening around the country to help cities adapt to shifting and intensifying weather patterns.

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California's flooding reveals we're still building cities for the climate of the past

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KWONG: California has been hammered by a parade of winter storms.


UNIDENTIFIED REPORTER #1: With now the eighth atmospheric river in just 16 days.

KWONG: Rivers and streets have flooded, levees have broken, and thousands have been evacuated.


UNIDENTIFIED REPORTER #2: So we'll see a couple of areas approaching flood stage, if not reaching that flood stage.

KWONG: And it's not just California that's experiencing these disasters. On a planet that's getting hotter, these extremes just keep coming. So we wanted to know, what can we learn from these storms? How can we be better prepared for these disasters? Well, Lauren Sommer from NPR's climate desk is here with me to help answer that.

LAUREN SOMMER, BYLINE: Yes. And I've got three innovative things that people are trying that could help make this a bit better, and they all have something in common. It has to do with a rethinking an underlying assumption that's baked into all of our buildings and cities and water systems because, you know, that's where the risk comes from, right? It's not the weather alone that's a problem; it's how it impacts the stuff we've built.

KWONG: Right. Yeah. You could say that so much of the damage and destruction is actually driven by how and where we've chosen to live.

SOMMER: Yeah. And all of that built environment around us was designed for certain weather. So when you step over, like, a storm drain in the gutter, that's designed to handle a certain amount of rainfall. When you walk on a levee next to a river, it's designed for the flow of the river. And we've always used the past as a guide.

KWONG: Yeah. But with climate change, that's a big problem because now weather patterns are changing.

SOMMER: Exactly. The future is not going to be like the past. Rainfall is getting heavier from storms, and the assumption that we've made about what our neighborhoods can handle just isn't true anymore.

KWONG: So today on the show, three big lessons from California's severe storms and what cities and communities are trying out to be better prepared for next time. You're listening to SHORT WAVE, the daily science podcast from NPR.


KWONG: So, Lauren, what's strange about what the West has been going through is that even with all this water, there's still a historic drought going on.

SOMMER: Yeah. I can say that, you know, living here in California, it's a big disconnect. The reservoirs started out extremely low, so it's really only now that those levels are finally getting up there.


SOMMER: Some are still below average, though. But there's so much water and rain, there's just a lot of runoff and flooding all over the state. And that has a lot of people asking, how can we save more of this floodwater for the dry season?

KWONG: Ooh. So that sounds like innovation No. 1. That's possible. But I'm guessing just scooping up that floodwater is not that simple.

SOMMER: No, not quite because today there's actually this rule that's working against that in some cases, and it's that reservoirs are not allowed to be full in the winter. They have to empty themselves out.

KWONG: Really? That doesn't seem like a great idea for a state with a lot of drought.

SOMMER: Yeah, I could see that.

KWONG: Yeah.

SOMMER: But reservoirs actually have two jobs. They do store water for when it's dry. But in the winter, they also have to catch the runoff from storms so that it doesn't flood cities and towns downstream. They can't do that if they're full because the dams could be easily overwhelmed by a lot of water. So that's why reservoirs have these automatic rules that say, in late fall, they have to release a certain amount of water if they have too much.

KWONG: OK. So reservoirs - partially empty to be able to take on more water. How much water are they releasing?

SOMMER: So one example - there's this big reservoir outside of Sacramento, Calif., called Folsom Reservoir. The rule there said it could only be 60% full of water in the winter at the most. So, you know, sometimes the reservoir would empty out millions of gallons when it didn't really need to because no big storms arrived after that.


SOMMER: So now they're trying something else, which is to dynamically manage the reservoir using the weather forecast. So the reservoir - yeah, it doesn't empty out preemptively. It only does if a big storm is on the way.

KWONG: That is so neat and just feels very futuristic that the forecast could determine what the reservoir does. But that means the forecasts need to be pretty accurate.

SOMMER: Yeah, it really does. And there actually is a research team that's working on that right now.


UNIDENTIFIED PILOT: Power's set. Airspeed's alive.

SOMMER: So those are the NOAA Hurricane Hunters. That's the National Oceanic and Atmospheric Administration. And earlier this month, they were on a mission to fly into an atmospheric river.

KWONG: They don't just track Santa Claus, people. We just did an episode about these storms that stretch hundreds of miles.

SOMMER: Yeah. They're like these rivers of moisture in the sky. And from 45,000 feet, that team releases special instruments called dropsondes. They kind of look like burritos with parachutes.


UNIDENTIFIED PILOT: Three, two, one, mark. Release sondes now.

SOMMER: So the instruments gather vital data about the storm, which is helping forecasters better predict exactly what atmospheric rivers do. And that, in turn, is helping these reservoirs that are trying to dynamically manage their water.

KWONG: Lauren, is managing reservoirs this way something that could help California's drought this coming year?

SOMMER: It could, you know, especially if there's a repeat of last year where the storms kind of just dried up after January.

KWONG: Yeah.

SOMMER: And as the climate gets hotter, this could be a pattern California sees more of. That's what Marty Ralph, who studies reservoirs at UC San Diego's Scripps Institution of Oceanography, told me.

MARTY RALPH: Longer droughts, deeper droughts and bigger storms between them. So we need to prepare. There's a lot at stake, and these are methods that could really help us with climate adaptation.

SOMMER: It's just two reservoirs in California doing this now, but a handful of others are studying it to see if it could work there, too. It's a big shift because it's changing water rules that were created, you know, half a century ago, when many of these dams were built.

KWONG: OK. So that is the first innovation - retrofitting reservoir use to the weather forecast. What is the second?

SOMMER: OK. So No. 2 - we were just talking about rivers, but that's not the only reason we saw so much flooding in California. There were flooding problems, you know, in neighborhoods and streets that were not even close to rivers.

KWONG: So it was just because of rainfall, then? Like, a huge amount of water from the sky hit a lot of pavement and flooded everywhere?

SOMMER: Yeah. That's what happens. It's this overwhelming amount of water. And the stormwater infrastructure, which is those drains and pipes that go underground, they're just not designed for that much water.

KWONG: Is that because the stormwater infrastructure itself was designed based on, like, old rainfall records?

SOMMER: Yeah. That's it exactly, right? It's these really old rainfall records from decades ago.

KWONG: Yeah.

SOMMER: But we're still using them today. Like, I spoke to the Louisville and Jefferson County Metropolitan Sewer District in Kentucky, their water utility. And their stormwater infrastructure is based on rainfall data from 1961.


SOMMER: The problem is that storms are getting more intense, right? And the utility did a study that found extreme rainstorms have already gotten worse and, with climate change, will drop 2 to 3 more inches of rain by 2065.


SOMMER: Infrastructure planning manager Stephanie Laughlin says, you know, they are feeling those effects.

STEPHANIE LAUGHLIN: Because those climate change storms are happening more frequently, now is the time to invest in updating those systems that were installed a hundred years ago.

KWONG: Yeah. So why don't utilities just switch to more recent rainfall records to design their infrastructure?

SOMMER: Some big water utilities are doing that. But in general, the problem is that they rely on the official rainfall data from the federal government. That's put out by NOAA. In late December, President Biden signed a law that requires NOAA to update these records for the entire country and to include climate change forecasts about future storms for the first time. So NOAA is already working on that update.

KWONG: OK. Which would give everyone, even California, that data, too.

SOMMER: Yeah, that's right.

KWONG: And, Lauren, I know infrastructure is a big focus right now of the Biden administration. Congress passed the bipartisan infrastructure law, and billions of dollars are being spent. But will NOAA's nationwide weather update be ready in time for all those projects?

SOMMER: No. For the most part, no. The problem is that NOAA won't have that new climate data until 2026, and the vast majority of the infrastructure funding - and that's almost $12 billion for these water systems - will be distributed by then. You know, I talked to NOAA, and the officials there say it will take that long because doing the analysis for the whole country is pretty complex.

KWONG: So what should cities and states do in the meantime if they're planning big water projects to make sure that they're ready for climate change, but they're being, like, mindful of data they don't even have?

SOMMER: Yeah. That's the key issue they're facing because what's built today is going to last, you know, 50, 60 years, even longer. I spoke to Rachel Cleetus, who works on extreme weather policy with the Union of Concerned Scientists, about this. And she said even without this updated rainfall info, cities need to build in, you know, some kind of margin of safety to deal with climate change.

RACHEL CLEETUS: What we need to do is make sure that we're mainstreaming it into all of our infrastructure decisions from here on out. Otherwise, we will be putting good money after bad. You know, we will have roads and bridges that might get washed out. We might have power infrastructure that's vulnerable.

KWONG: Right. It's that same shift in philosophy - that the past isn't a great guide to the future anymore.

SOMMER: Yup. You got it. And there's one more way that's happening. And this is innovation No. 3. And for that, we're going to take a little trip into the past.

JOHN CARLON: It looks like a bomb's gone off is what it looks like.

SOMMER: So that's John Carlon. And back in 2017, I was going down the Feather River with him in Northern California. He ran River Partners, which is a nonprofit that does river restoration, though he recently retired. We were looking at damage from the last big flood on that river, and it really looked grim. You know, the levees that separate the river from the land, they were just eaten away with these huge gouges in them. But then we went to this spot that was downriver a little bit.

Here, the riverbank has brush and trees.

CARLON: Cottonwoods and willows and Sycamores.

SOMMER: And they're caked in mud almost over our heads, showing just how high the floodwaters rose. But that makes Carlon grin.

CARLON: It's absolutely amazing to see. It's designed to take that.

SOMMER: It's an area that's supposed to flood. More than a decade ago, the levees were right up next to the river, like a lot of the rest of the river. But then the levee was moved back by about a quarter mile to make this space that acts as a floodplain. So when the river is running high, the water can just spread out there.

KWONG: OK. So it gives the water somewhere to go so it doesn't do as much damage.

SOMMER: Yeah. It gives the river room when it needs it, and that's how rivers are supposed to work. We tend to, you know, think of them as these relatively static things. We put buildings right up to the edge. But rivers are meant to expand and shrink with the seasons. And by channelizing them and making them narrow, the water moves really fast and can easily cause more flooding.

KWONG: That makes a lot of sense. But what does a change like that mean for people who already live along the riverbanks, who have their homes there?

SOMMER: Yeah. That's the hard part because you have to buy out the properties and relocate people or just get people to sell the land. And all of that is really tricky and expensive to do.

KWONG: Yeah.

SOMMER: So, so far, it's really just a handful of projects around California where they've been able to make this work. But, obviously, the costs from flooding are also huge, so it's kind of relative.

KWONG: Yeah. It's going to take a lot of money and a lot of time and convincing to change the infrastructure that we had, and it is based on rethinking about how we plan things in the first place. If storms and floods will get worse, we probably need to change how we build around rivers moving forward.

SOMMER: Yeah. It's just that predictability isn't there anymore. And with all of these examples, you know, whether it's reservoirs or using weather data or rethinking our relationship with rivers, people are finding ways to adapt to that future. It's just it might take some time.

KWONG: Lauren Sommer, thank you for bringing us this perspective and this reporting.

SOMMER: Yes. Always happy to.


KWONG: This episode was produced by Berly McCoy. It was edited by supervising producer Rebecca Ramirez and fact-checked by Anil Oza. Brendan Crump is our podcast coordinator. Beth Donovan is our senior director of programming. And Anya Grundmann is our senior vice president of programming. I'm Emily Kwong. Thank you for listening to SHORT WAVE, the daily science podcast from NPR.


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