Published on December 29th, 2017 | by Steve Hanley0
Shanghai Experiments With “Sponge City” Technology
December 29th, 2017 by Steve Hanley
Like many world cities, Shanghai is a port city located on the edge of the ocean. It it vulnerable to flooding from the sea as well as rain from above. Following serious flooding in Beijing in 2012, the Chinese government made water resiliency a priority for its cities. The plan is to create “sponge cities” — communities that can absorb large quantities of water and retain it until it can be slowly dispersed back into the environment. The concept involves green roofs, wetlands, natural vegetation, and one other component — permeable concrete.
The “sponge city” concept now applies to 30 cities in China. Like the others, Shanghai is wrestling with how to implement the requirements imposed by the central government, which has learned the magic of the unfunded mandate from the United States. Even though the government now stresses resiliency, it provides only about 20% of the money needed to carry out its dictates.
There are parallels between Shanghai and Houston. Both have experienced rapid economic growth, which has led to paving over much of the surface area of both cities and disrupting natural water collection areas such as ponds, lakes, streams, and marshes. “In the natural environment, most precipitation infiltrates the ground or is received by surface water, but this is disrupted when there are large-scale hard pavements,” says Wen Mei Dubbelaar, director of water management in China, according to The Guardian. “Now, only about 20–30% of rainwater infiltrates the ground in urban areas, so it breaks the natural water circulation and causes waterlogging and surface water pollution.”
“The first thing is to try and preserve or restore natural waterways, because that is the natural way to reduce the flooding risk,” says Prof Hui Li of Tongji University. “In Wuhan, for example, the main problem is that a lot of small rivers were filled in during building. That is a benefit the Lingang area has, as there is still a lot of agricultural land and a manmade lake which has capacity to hold more water during heavy rain. In the past, humans have taken the land away from the water; now we need to give the land back.”
“Sponge city infrastructure is beneficial because it is also changing the living environment, helping with pollution and creating a better quality of life in these areas,” says Dubbelaar. “The initial driver for sponge cities was the extreme flooding of urban areas, but the change in mindset, that development should have a more holistic, sustainable approach, is an extra benefit that is evolving during this project.”
Retrofitting congested city centers is difficult and expensive. It is easier to start with outlying areas where growth has not yet consumed every square inch of land. Shanghai is focusing on the Lingang neighborhood, which is less built up than the central city. In addition to the environmental benefits, resilient cities are also more pleasant places to live and work.
A visitor from out of town says she has never heard of the term “sponge city” but likes the idea. “I like all the trees and parks,” she says.“It doesn’t really feel much like a city. I think it’s much more pleasant than other parts of Shanghai.” Resiliency has a positive impact on quality of life issues, which may be more important than economic benefits to the people living there. Not all parameters of human happiness come with a price tag attached.
Hat tip to Are Hansen