Scientists create spongy city roofs that can soak up rainwater to help curb flooding: ‘Applicable to many urban areas around the world’

June 7, 2024 | by

Amsterdam and other cities have embraced a “sponge city” design concept that allows buildings to absorb rainwater.

Resilio is a project installing 100,000 square feet of climate-adaptive roofing on buildings — including social housing complexes — throughout Amsterdam. This system goes a step beyond green roofing to create blue-green roofing that can store excess water, according to The Guardian.

Here’s how it works: A layer of plants (usually a combination of grasses, mosses, ferns, shrubs, herbs, and sedum) is rooted in soil that provides support. The plant layer sits atop a filter layer that separates it from crates that store the excess water, plus extra layers at the bottom to separate the crates and plant roots from the roof.

“You have, in fact, a flat rain barrel on top of your roof,” Kasper Spaan, a policy developer for Amsterdam’s public water company Waternet, told the outlet.

The blue-green roofs’ smart valves can detect forthcoming downpours and release excess water beforehand so the roofs can absorb a new wave of rain. The Guardian describes this process as the roof becoming “a sponge that can be wrung out as needed.” The roofs also have the power to cool the buildings they sit on and may even be able to grow crops within them in the future. And that’s not to mention the possibilities of combining these roofs with solar panel systems.

Systems like these spongy roofs can help us prepare for and lessen the effects of an excessively hot future, as their plants absorb carbon dioxide and help mitigate flooding in heavy rain. Other promising architectural advancements are helping make similar improvements to buildings, including greener concrete materials, innovative mirroring designs, and earthen materials.

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“Our philosophy in the end is not that on every roof, everything is possible,” Spaan said, “but that on every roof, something is possible.”

“We think the concept is applicable to many urban areas around the world,” he added.

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