Courtesy of Mr. De Ducdoctel
Underneath is a filter layer that prevents soil from entering the next layer, a lightweight box system that stores water. And finally, underneath there is an additional layer to prevent water and plant roots from seeping into the actual roof. “We actually have a flat rainwater tank installed on the roof,” says Kasper Spahn, climate adaptation policy developer at Waternet, an Amsterdam public water management organization that is part of RESILIO.
The water level on the turquoise roof is controlled by smart valves. If the weather forecast calls for a storm, the system releases stored water from the roof in advance. That way, during a downpour, your roof will fill with water and there will be less rainwater entering surrounding gutters and sewers. In other words, the roof becomes a sponge that the operator can squeeze as needed. “In a ‘squeezable’ sponge city, the entire city becomes flexible,” Spahn says.
This makes traditional stormwater management systems more flexible, but also more complex. So the RESILIO project used Autodesk software to model the impact of Amsterdam's turquoise roofs and flood risk, while also adjusting for climate change.
“We can look at historical flood patterns and run simulations to help us understand. If we can remove this much capacity from our drainage network, we can reduce 10 floods when a storm comes.”15. 20 percent,” said Amy Bunzel, executive vice president of architecture, engineering and construction design solutions at Autodesk. “So our software allows us to run simulations and try different trade-offs.”
Beyond the sponge city benefits, the turquoise roof cools the top floors of the building, essentially draining away stored water from “sweat.” Using the right types of native plants can also increase biodiversity by providing food for native pollinating insects. Going a step further, scientists are also experimenting with growing crops under rooftop solar panels, known as rooftop agrivoltaxing. In theory, combining this with a blue-green system could actually improve the efficiency of solar panels by cooling them with the water that evaporates.
