NewRoFoundation

For her project seeking to design a better “green roof,” Yaffa Segal treated stormwater as if it had a mind of its own.

She designed a roof using COBWEB, software generally used to model the movements of organisms’ “agency,” or the ability to control what they do. Segal preferred it to other software designed specifically to model stormwater’s path because of COBWEB’s graphic possibilities, in addition to its data generation.

“The end goal is more exploratory, to push the limits of this program and see if it’s capable of hydrological modeling,” she said. “If you have a green roof that’s accurate enough, you can use this model to change the factors before you use it.”

She created the virtual roof in an 80-by-80 grid, incorporating stones and plants to block or absorb the water.

“Ultimately, what we want is a roof that can slow the rate of water absorption into the sewage system,” she said.

Early simulations moved stormwater too quickly for her to get a good look at what was happening.

“I can definitely keep going to improve the results,” she said. That could mean adding more plants with roots.

Segal has always been passionate about the environment, and her project is timely. A 2019 law in New York City requires all new buildings and those undergoing significant roof repairs to include solar panels, a green roof or a combination of the two.

Roofs can be planted with a wide variety of vegetation. Tall grasses and leafy vegetables such as cabbages make good choices, but the types also change with the seasons. Whatever plants are chosen, the roofs do more than slow the movement of stormwater. They also help cool buildings and restore green space taken from cities during development. That can benefit wildlife not often associated with urban spaces, such as bees and types of birds. (An earlier project of Segal’s tested honey samples from urban beehives for heavy metals.)

“You don’t think of New York City having a thriving ecosystem,” she said. “But that can be fixed with so much added green space.”