Possible Remedy for Urban Floods: 'Sponge Cities'

He is sometimes called the Frederick Law Olmsted of China, notes NPR. Meaning landscape architect Yu Kongjian is compared to the famous American who put Central Park amid the skyscrapers. As the NPR story explains, the modern movement Yu is spearheading goes well beyond aesthetics. It's summed up in a two-word description: sponge cities, and the idea is to ease flooding that seems to be getting worse by the year in the world's urban areas. "Think more parks and fewer parking lots," is how a piece at Wired sums things up, one that advocates for cities such as New York and Los Angeles to get "spongier" in the very near future. The idea is to move away from concrete and the like and revert to more natural landscapes that can better handle rainfall.

"Traditionally, our cities are designed to resist water and remove it very quickly: water is directed by hard surfaces like concrete into drains, which take water into underground pipes that lead from cities into rivers, lakes, or the ocean," explains Usman T. Khan at Macleans in Canada. The problem is that all those "hard surfaces" make it impossible for water to soak into the ground or evaporate. Plus, those underground pipes were built when average rainfall was lighter. Today, "more frequent and serious storms have overloaded this outdated infrastructure." The upshot, then, is that instead of trying to repel water, sponge cities welcome it.

China has perhaps been the most aggressive in pushing the concept, thanks largely to Yu, though Reuters notes the limitations. The city of Zhengzhou, for example, has made big investments in such changes, but it was nevertheless devastated by record rainfall in 2021. At Wired, Matt Simon points out that cities can adopt elements of the concept in piecemeal fashion: permeable pavement, more green roofs and green spaces in general, perhaps stormwater fees for neighborhoods that have way more pavement than vegetation. "The city of the future may be spongier in ways that are obviously verdant or more subtle," he notes. (More flooding stories.)