Most architects look to control nature; Kongjian Yu wants it to take over.
Intense storms are on the rise and cities across the world are finding it difficult to cope with deluges of floodwater. But instead of using high-tech, concrete-based engineering solutions to defend against the vagaries of the climate crisis, the Chinese landscape architect and urban planner lets nature do the work.
For over a decade, Yu and his firm Turenscape have designed nature-based “sponge cities” intended to soak up and retain stormwater before releasing it back into the environment. Varied in form and scale, the projects create new parks, restore wetlands and install rain gardens and permeable pavements, among much else.
The problem with concrete- or pipe-based solutions that funnel water away from flooded areas is that they are expensive, lack flexibility and require constant maintenance, Yu said. They may also, counterintuitively, make places more “sensitive or vulnerable” to flooding, he argued, comparing cities that rely on conventional flood mitigation to a person whose veins and arteries have hardened. Just as reduced blood flow causes heart attacks, blockages and overflows in urban drainage systems can have devastating knock-on effects.
“There’s a misconception that if we can build a flood wall higher and higher, or if we build the dams higher and stronger, (then) we can protect a city from flooding,” Yu told CNN in a video call. “(We think) we can control the water… that is a mistake.”
Yu’s proposal is this: Create areas with porous earth where local plants can thrive with little or no maintenance. If it rains, the earth and plants soak up the water and prevent some (or even all) of it from flooding nearby areas. Any excess water that is not absorbed will at least be slowed by the vegetation — unlike concrete, which can instead dangerously speed up water flow, Yu said.
Turenscape has planned and designed over 10,000 of these projects in more than 250 cities across the globe, completing over 1,000 of them. Many are found in China, where more than 70 cities have implemented sponge city initiatives (not all are by Turenscape, as some local governments have used other firms) since the country incorporated the idea into national urban planning policy in 2015.
Floods present a growing problem in China, with Chinese leader Xi Jinping calling the task of controlling them “increasingly arduous” in late June. According to a 2021 World Bank report, 641 of China’s 654 largest cities face regular flooding. This has partly been attributed to rapid urban development, which has created sprawl that encases floodplains in impermeable concrete.
China’s vulnerability to flooding has been thrown in stark relief this summer. In June, southern parts of the country were hit by flash floods and deadly landslides following torrential rain, with tens of thousands of people evacuated.
Last month, similar devastation played out across China’s heartlands as multiple provinces declared emergency alerts and dozens of people were killed amid scenes of deadly bridge collapses, cities submerged in water and emergency responders in speedboats racing to rescue stranded residents.
But whether this latest flooding crisis demonstrates the limitations of China’s sponge cities, or supports the case to expand them, is a matter of debate.
Keep reading about the "sponge cities."
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