China turns cities into sponges to stop flooding
China’s rapid urbanization and changing climate have made urban flooding a growing crisis. Many of its cities, covered in concrete and asphalt, lack natural drainage, causing heavy rainfall to overwhelm traditional flood control systems.
Flooding events have become more frequent and severe, causing billions of dollars in damage annually. In 2021, for example, record-breaking floods in Zhengzhou submerged entire neighbourhoods, paralyzed transportation, and claimed nearly 400 lives. The economic losses from these floods exceeded $10 billion.
Traditional flood management methods, such as concrete drainage channels and dams, are often insufficient to handle extreme rainfall. These systems move water away quickly but fail to address the root causes of urban flooding, such as excessive runoff and poor water retention. Recognizing these challenges, China has turned to a more sustainable, nature-based solution.
The sponge city concept is built on the idea of absorbing, storing, and slowly releasing rainwater rather than simply channelling it away. Inspired by natural ecosystems, sponge cities incorporate green infrastructure that helps manage stormwater more effectively.
Key features of sponge cities include:
- Permeable pavements that allow water to seep into the ground instead of running off into streets.
- Green roofs are covered with vegetation to absorb rainwater and reduce runoff.
- Rain gardens that capture and filter stormwater, preventing it from overwhelming drainage systems.
- Constructed wetlands that store excess water while improving water quality.
- Bioswales, or vegetated channels, that slow down and filter stormwater before it reaches larger waterways.
These features help cities function more like natural landscapes, reducing flood risks, conserving water, and improving urban environments.
The sponge city initiative offers multiple benefits beyond flood prevention. By absorbing and storing rainwater, sponge cities reduce surface runoff by up to 70%, significantly lowering the risk of flash floods. This prevents homes, businesses, and infrastructure damage while keeping streets safer during heavy rains.
Instead of letting rainwater go to waste, sponge cities store and reuse it for irrigation, groundwater recharge, and even drinking water supply. This is particularly valuable in water-scarce regions, helping to alleviate urban water shortages.
Sponge city features improve water quality by filtering pollutants before they enter rivers and lakes. Green spaces also support biodiversity, combat air pollution, and help cool down urban areas, reducing the urban heat island effect.
Green infrastructure investments reduce long-term costs by minimizing flood damage, lowering water treatment expenses, and decreasing reliance on expensive drainage upgrades. Cities that embrace sponge city principles can save millions of dollars annually in disaster recovery and infrastructure maintenance.
Beyond water management, sponge cities enhance urban livability. Parks, wetlands, and rooftop gardens create more recreational spaces, improving residents’ quality of life and fostering a stronger connection to nature.
Since launching the program in 2015, China has designated 30 pilot cities, including Beijing, Shanghai, Wuhan, and Shenzhen, to integrate sponge city principles into urban planning. By 2030, the government aims for 80% of China’s urban areas to have sponge city infrastructure capable of managing at least 70% of their rainwater. As climate change intensifies flooding worldwide, cities from New York to Jakarta are exploring similar approaches.
China’s sponge city program is reshaping urban water management and building resilience against climate change. By integrating nature into city planning, China is not only reducing flood risks but also creating healthier, greener, and more livable urban spaces.
As extreme weather events become more frequent, sponge cities offer a sustainable blueprint for the future of urban development. Whether in China or beyond, cities that embrace these principles will be better prepared to face the challenges of a warming planet while improving the quality of life for their residents.
