Sponge City

Ancient Technology for Future Generations
A flood-resilient planning and landscaping initiative that harnesses ancient technologies of vegetal filtration to slow and absorb flood water, while also creating areas of biodiversity that reduce the city’s heat and pollution


To achieve climate justice, both construction and occupation of spaces require a long-term way of thinking that anticipates impacts on future generations, and resists temptations to make money in the short term. Often, ancient knowledges and practices provide useful models for how to construct and use space, because such “technologies” have been tried and tested over generations. Modern technologies, on the other hand, sometimes conceal their long-term environmentally damaging implications behind short-term promises of quick-fixes which act as band-aids rather than genuine change for good. The contrast between ancient and modern methods of flood management is one such example.

Ancient farming techniques understand that storing rainwater in ponds is an efficient way to provide water for crops, cool air temperatures, and encourage biodiversity. Across the world, modern urbanism has ignored this wisdom and concreted over cities and their hinterlands with vast road infrastructures, settlements, buildings, and paving. In the face of more severe floods linked to rains exacerbated by global warming, such sealed-off urban areas and their occupants are at risk. Conventional flood management involves building pipes and drains to carry water away quickly. Concrete is often used to reinforce river banks and prevent overflow. Homes are built near rivers and coastlines despite risks of flooding. Such practices separate humans from nature, people from water… until the pipes and banks burst, and homes flood or wash away. Monsoon climates and flooding caused by climate breakdown are too powerful for these conventional constructions in unwise locations. China’s expanding population and economic power makes it one of the world’s fastest urbanising regions and, because of its reliance on modern technologies and practices, one of the most vulnerable to flooding.


Considering this context and drawing from ancient farming techniques of water storage he learned as a child in rural China, in 2000 the architect Yu Kongjian coined a method to soak up rainfall and slow down surface run-off. The “Sponge City” method has since spread across many cities and regions. The method is not new: it derives from traditional, low-impact agri- and aqua-culture. But Yu’s succinct promotion of the method and its successful uptake by municipal authorities across China indicates an important step in reforming urban design through looking to ancient techniques, and working collaboratively in alliances of architects, farmers, urban developers, planners, and politicians.

Sponge City designs pond spaces within the urban fabric, so that the city acts like a sponge with many holes. In the event of a flood, instead of trying to channel water away in straight lines, Sponge City uses meandering rivers with vegetation to slow the flow of water. Wetlands around the ponds also help absorb the flow. These wetlands have additional benefits of providing community green-space, and purifying the water and air through toxin-absorbent vegetation. Sponge City avoids construction on low lands liable to flooding, using this land to absorb water. Urban heat intensity decreases in Sponge Cities, while human and animal wellbeing increases (cities have reported improved respiratory health, cardiovascular health due to new walking routes, and lower rates of obesity and diabetes).

While municipal authorities who introduce Sponge City as a system may use it as a form of greenwashing that creates pleasant greenspaces and vistas for developments without questioning the environmental impact of development itself, the concept nevertheless has rich potential. To implement Sponge City while focusing on climate justice, it is vital to consider its social impacts: does the construction of ponds displace a community? If so, what provisions are in place for that community to survive elsewhere, away from the flood plain? Are ponds also located in poorer neighbourhoods to ensure that Sponge City is not simply a leisure facility for affluent areas? Does Sponge City help existing communities and buildings, or is it being used for new-build sites and therefore for bolstering environmentally unfriendly and carbon intensive urban growth? Such questions are vital in realising Sponge City’s capacity for social and ecological care.

External links

Chennai’s Eri network—water storage from the monsoon rains 

How sustainable drainage (SuDS) offers a variety of important environmental, economic and social benefits 

Copenhagen’s municipal planning—for rainfall and flooding