The Secret Weapon to Fight Flooding Is Hidden in Plain Sight

It looks like and feels like a regular street. But beneath the surface, six layers are working to keep rainwater from overwhelming New York City neighborhoods.

This is Street Wars, a weekly series on the battle for space on New York’s streets and sidewalks.

It was a sunny day in Borough Park, Brooklyn, and city officials were standing in the street, staring at the pavement.

A man in a hard hat and yellow vest turned on a hose, and water flowed out onto the street. Most streets are covered in standard asphalt, a hard surface that water pools on top of. But in this case, the water disappeared, seeping through the pavement before it reached the curb.

This was permeable pavement, and it might already be on a street near you: In the last fiscal year, New York City’s Department of Design and Construction has installed about four miles’ worth of the porous material.

You might not even recognize it if you see it, because aside from its slightly lighter color, it looks and feels like any other pavement. Your car could be parked on it right now.

Many New York City neighborhoods are prone to flooding — and climate change means the problem is only getting worse. In order to understand why, I reached out to Bernice Rosenzweig, a professor of environmental science at Sarah Lawrence College and a contributor to a new report on flooding in New York City.

“We’ve replaced almost all of our natural surfaces with buildings, with streets, with sidewalks, with anything that’s paved,” she said.

In fact, 70 percent of New York City is made up of hard surfaces like pavement, which prevent rain from reaching the earth’s soil, said Melissa Enoch, the acting assistant commissioner of the city’s Department of Environmental Protection.

“We have to take every opportunity we can to try to soften our landscape and allow for storm water to infiltrate into the ground,” said Enoch, who was on the team of city officials overseeing the installation of the permeable pavement.

Rosenzweig noted that flooding is a “natural process” — a fact of life that’s hard to avoid entirely.

“Even if New York City hadn’t completely paved over everything and replaced our streams with sewers, there are still times when flooding would occur,” she said.

But as extreme rainfall increases, the problem becomes more urgent. When it rains, if water can’t soak into the ground, it flows into a sewer system that is more than 150 years old. About 60 percent of New York’s sewer system combines storm water and sewage in the same pipes. If there’s overflow, the delightful mix of rain and untreated sewage spills straight into local waterways like the East River.

This new kind of porous surface could make a big difference.

The city started piloting the technology back in 2017. After tweaking things in a research and development phase, officials have had “great success,” Enoch said.

The pavement is installed in strips that stretch for an entire block, parallel to the curb. It’s almost like a covered gutter, between the curb and the street. On some blocks, it’s two feet wide; on others it’s four feet wide.

Sofía Zuberbühler-Yafar, the assistant commissioner of the infrastructure design unit at the Department of Design and Construction, joked that installing the pavement requires “a lasagna” of elements.

On top, there’s the six-inch-thick porous panel. Below that, there’s a layer of small stones that keeps the panel level. Underneath are bigger stones that help drain the water. Beneath those, there’s a layer of plastic crate-like membranes. Finally, there’s the soil.

The lasagna design helps direct the rain into the ground, keeping it out of the sewer system.

Ted Timbers, a spokesman for the Department of Environmental Protection, said that when flooding happens, “if the sewer is full, the water starts backing up the pipes into people’s homes.” (Disgusting!)

The pavement is only one of New York’s initiatives around green infrastructure, said Elijah Hutchinson of the Mayor’s Office of Climate and Environmental Justice. “We’re building out rain gardens and bio swales and cloudburst projects, and all of those things are really going to help us adapt,” he said.

Of course, in New York, nothing is ever easy. Installing new pavement means digging up part of the street, where very important things are hidden, including electric, phone and gas connections.

“There’s a lot of coordination with utilities,” Zuberbühler-Yafar said, before clarifying: “negotiations with utilities.” Sometimes Con Ed or National Grid will have to relocate their service lines.

Then, even if the city finds a good location, Hutchinson said the soil has to be tested to make sure it’s in the right condition.

Certain parts of the city are built on bedrock instead of soft soil, and they may not be the best locations for porous pavement, since the water needs to be able to pass through and absorb into dirt. “You can’t put it everywhere,” Zuberbühler-Yafar said.

But the city has been identifying sites and moving forward. Already, a few big swaths of asphalt — some parking lots, schoolyards and at least one stretch in Rockaway — have been swapped out for porous pavement.

Often, when the porous section of pavement goes in near the curb, the city will also make the adjacent tree pits bigger, exposing more soil, which helps with rain absorption.

“Thinking about drainage and trees at the same time is really going to make sure we can utilize our streets in our fight against climate change,” Hutchinson said, adding that a street “can actually keep us cooler and drier if we design it and maintain it well.”

On the subject of maintenance: The pavement works best when it’s not covered with litter or leaves. It requires vacuum cleaning and high-pressure jet washing, and the city anticipates needing to clear it of sediment and litter twice a year, in the fall and in the spring.

When it comes to preparing the city for the effects of climate change, many experts believe it’s important to try a range of strategies.

“We cannot just rely on one best solution, because it doesn’t really exist,” said Yuki Miura, an assistant professor at New York University’s Center for Urban Science & Progress and its Department of Mechanical and Aerospace Engineering.

Miura models hurricanes and develops strategies to build resilient cities. And though some climate researchers have a dismal outlook, “I’m optimistic,” she said. “People are thinking about the risks of climate change every day.”

She added: “I’m working on this because I believe we can fix this.”

New York City plans to have installed 100 miles of porous pavement by 2031, Enoch said. Hutchinson recommended checking out the city’s green infrastructure map to see both completed and upcoming projects: “We’re coming to a block near you.”

Raised crosswalks are safer for pedestrians. But in New York City? They cost $800,000.

By Rose Adams

It’s a straightforward way to promote pedestrian safety: a crosswalk that doubles as a speed bump.

An upcoming city project plans to raise crosswalks across the five boroughs. These mounds of asphalt, which cut through dangerous intersections, have been proven to slow drivers down and reduce pedestrian deaths.

The New York State Department of Transportation puts the cost of building a raised crosswalk at $15,000. One in Pittsburgh cost $25,000 in 2021. So why is New York City planning to spend $105 million to elevate about 125 crosswalks, making each, on average, cost more than $800,000?

The project is part of Mayor Eric Adams’s 2022 initiative to build 100 crosswalks each year, which has rolled out slowly: Just 42 have been built since 2022. The city has chosen a contractor for the $105 million project, although details of the contract are still under negotiation, according to Ian Michaels, a spokesman for the Department of Design and Construction.

Transit experts say the high costs stem in part from the city’s old and densely packed streetscape. Traffic signals, streetlights and signage must be removed and reinstalled. You need catch basins to prevent storm water from pooling along the crosswalk’s edge. And in some cases, construction requires rerouting utility lines, revealing the dense knot of cables known as “underground spaghetti.”

“There’s no comprehensive database for where stuff is,” said Chris Jones, a fellow at the Regional Plan Association, an urban planning group. “So every time you open up the street, it’s like, ‘Oh, there’s a pipe there that’s got to be moved.’”

Much of the underground infrastructure isn’t even city property, forcing delays and negotiations. And some raised crosswalks require rebuilding recent upgrades, like accessible pedestrian ramps. (The push to install and revamp the city’s more than 210,000 noncompliant curb ramps, another major transportation project, will likely run over its $2.8 billion budget.)

New York City’s building costs are the highest in the country. And since intersections vary in size, no standardized design will work.

It’s a familiar story: An April review by the state comptroller found that more than half of city projects ran over budget and nearly two-thirds were delayed, many by more than three years.

Experts say projects get stuck in a sludge of regulations and reviews. “Outdated rules limit the city’s ability to build and cause delays,” said Alison Landry, the city’s chief infrastructure officer. “Something as simple as building a bathroom often takes years longer than it needs to.”

A slate of reforms, spearheaded by Ms. Landry, aims to modernize and streamline the building process. Now, the city invites contractors to help design many major projects, saving years of planning, and reducing costs by millions of dollars, she said. And as of this year, companies can submit construction bids electronically rather than by paper.

But, like the city’s construction, some of these changes are off to a slow start. A new digital dashboard — designed to make capital spending more transparent — lists budgets with scant explanation, making it nearly impossible to break down a project’s cost. Clarifying details hide in hundreds of pages of obscure filings, if they’re made public at all. With little information, even the government struggles to identify where the bloat is.

“The first step to improving the capital process is understanding where the barriers are right now,” said Louise Yeung, the chief climate officer at the city comptroller’s office, who tracks infrastructure investments. “Without that kind of insight, it’s difficult to pinpoint where these problems are.”

Enjoying our Street Wars series? Tell us what you like or how we could improve: streetwars@nytimes.com

What we’re reading

• Murders are down, but traffic deaths are up. [New York Daily News]
• The Washington Bridge, which connects Manhattan and the Bronx over the Harlem River, now has a dedicated bus lane and a protected bike lane. [6sqft]
• The mayor of London may ban cars from Oxford Street. [Bloomberg CityLab]
• The graffiti artist Futura — who once used New York’s streets and subway cars as his canvases — is the subject of a retrospective at the Bronx Museum of Art. [Gothamist]

Street Wars: The Battle for Space in New York

• A Chaotic Struggle for Space: New York City streets and sidewalks have always been crowded, but it’s never been like this. Now more than ever, the city is being forced to rethink how its thoroughfares are used.
• Crackdown on Street Vendors: The police have been ticketing vendors for violations over the past year, upsetting sellers who say they are just trying to earn a living.
• A Park Avenue Hang Out?: A glimpse at the future of one of Manhattan’s most famous streets — and a look at its history, from train tracks to illegal weed.
• Reclaiming Roads for Recess: The city’s Open Streets program will allow schools to close 71 streets to traffic and open them for students to play without worrying about speeding cars.
• Choosing Bikes Over Cars: The transformation of cycling access in Paris over the past few years may have lessons for New York and its car-clogged streets.