Excerpt from this story from the New York Times:
Cities around the world face a daunting challenge in the era of climate change: Supercharged rainstorms are turning streets into rivers, flooding subway systems and inundating residential neighborhoods, often with deadly consequences.
Kongjian Yu, a landscape architect and professor at Peking University, is developing what might seem like a counterintuitive response: Let the water in.
“You cannot fight water,” he said. “You have to adapt to it.”
Instead of putting in more drainage pipes, building flood walls and channeling rivers between concrete embankments, which is the usual approach to managing water, Mr. Yu wants to dissipate the destructive force of floodwaters by slowing them and giving them room to spread out.
Mr. Yu calls the concept “sponge city” and says it’s like “doing tai chi with water,” a reference to the Chinese martial art in which an opponent’s energy and moves are redirected, not resisted.
“It’s a whole philosophy, a new way of dealing with water,” he said.
Through his Beijing-based company, Turenscape, one of the world’s largest landscape architecture firms, Mr. Yu has overseen the development of hundreds of landscaped urban water parks in China where runoff from flash floods is diverted to soak into the ground or be absorbed into constructed wetlands.
Mr. Yu said growing up in a village in Zhejiang Province toward the end of the Cultural Revolution showed him how earlier generations in rural China had “made friends with water.” Farmers in his region built terraces, berms and ponds to direct and to store excess water during the rainy season.
That stood in sharp contrast to the urban landscapes in modern China. Traditionally, cities in China would set aside areas capable of absorbing floodwaters. But such nature-friendly urban design largely ended with the Industrial Revolution, Mr. Yu said. More recently, millions of acres have been paved over to build cities, some of them rising up virtually overnight.
The sponge city program was formally inaugurated by President Xi Jinping in 2015 with pilot projects in 16 Chinese cities and has since expanded to more than 640 sites in 250 municipalities around the country.
You can see the concept in Houtan Park, a mile-long strip of greenery along the Huangpu River in Shanghai that Mr. Yu designed on a former industrial site.
Terraces planted with bamboo and native forbs and grasses are bisected by wooden walkways that zigzag between ponds and constructed wetlands. The wetlands filter water, slow the river’s flow and provide habitat for waterfowl and spawning fish.
The goal, at least on paper, is that by 2030, 70 percent of the rain that falls on China’s sponge cities during extreme weather events should be absorbed locally rather than accumulate in the streets.
Whether enough land can be converted is a key question.