Your city is not ready for what is coming. The classic way to deal with stormwater is to move it out of town as quickly as possible through drains, sewers and canals. But that strategy is increasingly broken: As the atmosphere warms, it can hold more moisture, spawning wetter storms that can overwhelm this crumbling infrastructure. Your city was built for the climate of 100, 200, 300 years ago, but that climate no longer exists.
A hot new urban design strategy pioneered in China is to slow things down. Since 2013, China has implemented a national policy to transform its growing metropolises into sponge cities, collecting rainwater rather than disposing of it all. If engineers can slow water flow so it seeps into the earth instead of escaping—using rain gardens, decking, permeable pavers, and urban wetlands—it can simultaneously reduce flooding and replenish underground aquifers. This will become increasingly important as the planet warms and droughts intensify: the goal of sponge cities is to store water for emergencies, or, more accurately, to prepare for droughts.
“Whenever it rains, we try to preserve as much as possible,” said Yu Kongjian, founder of Beijing Turen Landscape Design Company, an advocate of the concept. “We slow down the flow of water and let the earth absorb the water. The sponge city will be an adaptive city, a resilient water system, a porous landscape.” All told, a recent study found, cities across the U.S. are likely to Absorbing billions of gallons of water, in part by following China’s lead and accelerating sponge projects. “Sponge cities are urgent, immediate solutions that allow cities to adapt to climate change, heat, floods and droughts,” Yu said.
This is what Benjakiti Forest Park in Bangkok, Thailand, looked like before and after the sponge transformation. (Move the slider to see the complete conversion.)
Yu was recently awarded the Oberlander Prize by the Cultural Landscape Foundation for his work on sponge cities, and WIRED sat down with the landscape architect to discuss how to make urban areas as sponge-like as possible and what to do about it All questions. and what metropolitan areas can do now to prepare for tomorrow’s increasingly chaotic climate.This conversation has been condensed and edited for clarity
Wired: One of the reasons this concept is so powerful is that you can do it at such different scales. In Los Angeles, they have vast sites—open areas hundreds of feet wide that allow water to seep into aquifers—but they also tear up thin strips of curbs and plant greenery.
Kongjian Yu: Sponge city can be opened any scale. Water is precious.If you retain water in your backyard, you don’t have to water your trees, you don’t have to water your garden, because the water is right down there—your treasure is there here. It’s done on an individual, individual, community scale.