For the first time, Yu feels he may be preaching to the converted.
In September, the government approved the development of 16 model “sponge cities”—an ecologically friendly alternative to the gray urban expanses of modern China, involving improved drainage systems and other infrastructure to facilitate the absorption and reuse of rainwater. These will require infrastructure retrofits of existing cities all over China, ranging from Xixian New Area in the north, with about 500,000 people, to Chongqing in the south, with a population of 10 million.
Each city will receive 400 million RMB ($63 million) per year for three years to implement projects.
“A sponge city is one that can hold, clean, and drain water in a natural way using an ecological approach,” said Yu, who is helping to coordinate the national project.
Traditionally, Chinese cities handled water well, Yu noted. “But in modern China, we have destroyed those natural systems of ponds, rivers, and wetlands, and replaced them with dams, levees, and tunnels, and now we are suffering from floods.”
China began experimenting with sponge-related urban design ideas more than a decade ago. In 2000, one of the first large studies involving low-impact development—a method of natural stormwater management—was used in the design of a housing block called Tianxu Garden in Beijing. During the flood of 2012, the apartments easily survived the disaster.
Yet it was only after the Chinese president Xi Jinping suggested cities “should be like sponges” that the term became trendy among urban planners and designers.
Tat Lam is CEO of Shanzhai City, a social-development incubator. At the end of 2013, he was involved in commissioning designs for a new town. “I was judging many submissions, and suddenly discovered there was a huge trend for people using the term ‘sponge city,’” he remembered. “Every submission included it.”
“It was clear from the proposals that from a practical perspective, no one knew exactly what it meant,” Lam acknowledged. “But the ideological concept had taken hold.”
It’s for this very reason that sponge cities could run aground.
China’s rapid urbanization has been an exercise in laying concrete. As Bill Gates (now famously) tweeted, between 2011 and 2013, China used more cement than the United States did over the entire 20th century. And concrete is not permeable.
Stormwater systems that send runoff into sewers are largely inadequate at the scale of major cities. “Until recently, many of the decision-makers and experts in the drainage industry supported a larger, gray-infrastructure, civil-engineering approach to water management,” noted Andrew Buck, an urban planner at the Beijing-based design firm Turenscape (which is led by Yu). “But most of these systems are overloaded, and urban floods happen even in moderate sustained rains.”