“In the past, humans have taken the land away from the water; now we need to give the land back.” – Professor Hui Li [Guardian 2017]
Faced with severe flooding in many cities across China, such as a major 2012 Beijing flood, the Chinese government announced the Sponge Cities Initiative in 2014 as a remedy. The national government identified 16 cities as pilot sites, soon adding another 14 cities, including Beijing. The sponge city concept represents a paradigm shift in flood management away from impervious surfaces and chutes meant to swiftly drain a city after a storm. By contrast, a sponge city aims to manage stormwaters by vastly increasing the amount of soft, permeable surfaces that can absorb water where it falls, filter it, and store it in vegetation, ponds and aquifers.
A sponge city aims to manage stormwaters by vastly increasing the amount of soft, permeable surfaces that can absorb water where it falls, filter it, and store it in vegetation, ponds and aquifers. |
According to the “Guideline of Sponge City Construction”, the target of the approach is to increase the area of urban land able to absorb surface water discharges by approximately 20%, and to retain or reuse approximately 70% of urban stormwater by 2020; and further reuse up to 80% of stormwater by 2030s. This means that the ideology of the Sponge City concept is not only addressing urban flood risk, but also taking a proactive approach to collection, purification and reuse of urban stormwater in Chinese cities to address future climatic extremes (floods and droughts) [Chan 2018: 3-4].
One of China’s new sponge cities, the Lingang/Nanhui district of Shanghai, is buildIng streets with permeable pavement, which allows water to percolate into the ground beneath, and planting rain gardens between lanes of traffic as well as some 400,000 square meters of rooftop gardens. In another city, the 84-acre Qunli Stormwater Park consists of a wetland surrounded by newly constructed filtering ponds that collect and filter the city’s stormwater runoff before slowly releasing it into the wetland, which in turn recharges groundwater. Earthen mounds are planted in cottonwood trees, and a system of elevated pathways through the park allows people to enjoy the space.
Inspiration for Qunli Stormwater Park and several other sponge city landscape design features comes from the ancient water management practices of Chinese peasants. According to landscape architect and sponge city advocate Yu Kongjian, peasants constructed simple terraces in combination with ponds to regulate flood and drought. “On sloping ground in monsoon regions these water catchments are critical,” Yu explains in an essay explaining the sponge city concept [Yu 2017: 29]. “Peasants also employed crop rotation to maximize yield, beautifully sustaining humanity for thousands of years” [Yu 2017: 29]. He continues :
Ironically, these centuries-old productive landscapes have given way to urbanization. Fine terraces are leveled into … planes called developable land; small ponds are drained and replaced with underground drainage systems; ponds and dikes give way to mechanical farming. The centuries-old ecosystem balance is broken, leading to flood, drought and habitat loss. Grey infrastructure haunts Chinese cities, while high maintenance landscapes with ornamental planting make broad scale landscape change unaffordable. [Yu 2017: 29]
China’s ‘sponge cities’ are turning streets green to combat flooding: https://www.theguardian.com/world/2017/dec/28/chinas-sponge-cities-are-turning-streets-green-to-combat-flooding
“Sponge City” in China: a breakthrough of planning and flood risk management in the urban context, Land Use Policy: https://www.sciencedirect.com/science/article/abs/pii/S0264837717306130
Yu, Kongjian, 2017, Sponge cities: rediscovering the wisdom of the peasant, Landscapes/Paysages Spring/Printemps 2017, https://www.csla-aapc.ca/landscapes-paysages/back-issues.
Chan, Faith Ka Shun, James A. Griffiths & David Higgitt, et al., 2018, “Sponge City” in China: a breakthrough of planning and flood risk management in the urban context, Land Use Policy, https://www.sciencedirect.com/science/article/abs/pii/S0264837717306130.
Swain, Daniel L., Baird Langenbrunner, J. David Neelin & Alex Hall, 2018, Increasing precipitation volatility in twenty-first century California, Nature Climate Change, https://www.nature.com/articles/s41558-018-0140-y.
Yu, Kongjian, 2017, Sponge cities: rediscovering the wisdom of the peasant, Landscapes/Paysages Spring/Printemps 2017, https://www.csla-aapc.ca/landscapes-paysages/back-issues.