Sponge Cities

China's 'Sponge Cities' project could help to address the country's water resources, flooding and water scarcity challenges.

The traditional idea of managing surface water runoff in an urban environment is to funnel that water away from cities as fast as possible. Recently, however, city planners and governments are realizing that this design concept is flawed as it means that they are, to all intents and purposes, throwing away a highly valuable resource: water. 

The new mode of thinking is to design a city in such a way that it retains all the surface water runoff that occurs within the confines of the city and that it can be reused at a later date, thereby creating an urban environment that absorbs the water then releases that water when required—in a similar manner to a sponge.

The Sponge City concept

The concept of a water-sensitive built environment is already established in many urban areas around the world on various scales through approaches such as sustainable drainage systems (SuDS) and low impact development (LID). China has embraced what it terms the 'Sponge City' concept because, combined with the facts of rapidly growing urban populations, poor water management and climate change, half of China’s 657 cities are reported to be water scarce. Of these cities 230 were affected by flooding in 2013 alone.

In 2013 Chinese President Xi Jinping called for the development of Sponge Cities and early in 2015 the Chinese Central Government pledged billions of dollars over the next three years to help 16 cities—including Wuhan, Chongqing and Shenzhen—to become Sponge Cities.

The benefit of the Sponge City approach

The main benefit to the population will be a better urban environment in terms of aesthetics and quality of life. Sponge City design allows the inhabitants to better enjoy where they live and work—and of course in addition the city has the ability to use their water resources far more effectively.

With increasing urbanization, if we continue to develop cities that don't take into account the capture, storage and reuse of water then we can expect more flooding, with rivers and lakes becoming even more polluted to the point that these water bodies die. There are numerous examples around the world of engineers having continued with traditional water management solutions only for the problems of flooding and water pollution to get worse.

At the same time, however, we see examples of engineers employing good, water-sustainable urban design where as a result the quality of the urban environment is dramatically improved and the incidence of flooding is reduced.

Difficult to adopt, less difficult to deliver

In the sense of getting governments, local authorities and municipalities to recognize the need to move away from the traditional paradigm of water management to that of water-sustainable urban design, Sponge Cities are difficult to implement. Once that mind shift happens and there is a will to change, however, then Sponge Cities will become relatively easy to develop.

In China alone the idea of Sponge Cities will grow far beyond the first 16 cities for which the Chinese Central Government has allocated development funds, and the idea is relevant to city planners all over the world—more and more governments are recognizing the need to manage their water resources more effectively. Increased urbanization, population growth and climate change will continue to drive the need globally for better, smarter and more sustainable water management solutions.

Popular misconceptions

The primary misconception around sustainable city design seems to be that there is only one solution, when the reality is that there is no 'silver bullet'. The best sustainable designs are those that use a combination of engineered products and natural features.

The other misconception is that the solution is expensive; relatively speaking this is incorrect, and the truism is that prevention is less expensive than the cure. Water is a hugely valuable resource that has no replacement and it is incumbent on today’s society to look after such a precious commodity.

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