When New York floods, this ‘living street’ stays dry

A new model for street design in the age of post-climate-change storms manages the water instead of trying—and failing—to keep it away.

When Hurricane Ida dumped record amounts of rain on New York City in late August, shutting down the subway and drowning some residents trapped in basement apartments, streets flooded in the Queens neighborhood of Rockaway Beach. Two weeks earlier, the same streets flooded in Tropical Storm Henri. But in front of one building, the pavement stayed dry.

“The whole neighborhood flooded,” says Walter Rodríguez Meyer, cofounder and principal urban designer at Local Office Landscape & Urban Design, which worked on the landscape design for the building—a mixed-use, 100% affordable complex called Beach Green Dunes. “Our site stayed bone dry.”

Around the building, permeable pavement—asphalt made with rocks that are all a similar size, which creates large pores—is designed to suck up water quickly in heavy rains. Under the pavement, “structural” soil, a mix of soil and a stone structure, is strong enough to be load-bearing but can also allow tree roots to grow freely and help absorb more water in storms. On roads, the approach is called a living street.

“Instead of a typical street tree, where a tree is by itself in the city, this means you network it to the next tree, and the next tree is able to reconnect like a forest,” Meyer says, noting that because of the way the system is engineered, it should actually be able to absorb more rainwater than a natural forest. Rain gardens and bioswales (plant-filled channels that can collect more water) replace more typical landscaping on the site. Another garden uses plants to help suck up groundwater on sunny days, so when a downpour happens, there’s more capacity underground.

One part of the complex, an apartment building completed in 2020, has a flood-proof lobby, and all of the apartments are on the second floor or higher, keeping residents above any potential floodwater. (The buildings also have solar panels on the roof, and could later be connected to batteries to help keep power on after major storms.) But the landscaping, designed for 1,000-year storms, should help prevent floodwater accumulation in the first place. Meyer says that during the recent heavy storms, a building manager reported watching the water rise on the nearby street, while simultaneously sinking underground on the property. The same thing has happened in other storms and during king tides.

The landscaping approach is something that makes sense across the city and any others prone to flooding, Meyer says. Current codes haven’t caught up with the reality of heavier rainfall and bigger storm surges because of climate change. “As the city is currently designed, stormwater is only managed in the 5-to-10-year capacity by code,” he says. “But we’re getting rain events that are 500-year events back to back.”

In a recent report from the nonprofit Regional Plan Association that considered how New York City’s streets could be reimagined—including making more room for people walking and on bikes, and more parks, green space, and other uses—the designers shared an example of how another heavily paved intersection could be transformed. A rendering shows a parking lot becoming green space, bike lanes separated by plantings, and more trees everywhere. “The street itself is totally porous, allowing water to infiltrate through the structural soil, the bike lanes, the sidewalk—everything you see on the right away is essentially porous,” says Tricia Martin, associate principal at Local Office Landscape & Urban Design.

Although that design, at the intersection of Northern Boulevard and Broadway in Queens, is just a concept, it’s the type of change that could realistically happen to help the city adapt to climate change, and something that the new city administration could potentially champion. “I think that the appetite for this is changing,” Martin says. “It doesn’t necessarily have to be more expensive. Because if you really do this at a systemic level, and network these trees and really start to reconstruct streets this way, you end up not needing pipes, and you don’t need to maintain pipes. And so you can start to see where there’s cost savings there.”

Living systems of “regenerative infrastructure” last longer, Meyer says. “There’s more capital costs—they cost between 30% and 50% more to build on the capital side, but the life costs are exponentially lower,” he says. “And when you calculate in how much more stormwater this processes, as well as the reduction in risk to insurance premiums for properties around it and for neighborhoods, then it’s an exponential payback.”

Source:- fastcompany.com


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