Social Sustainability
Sponge City
Definition
A sponge city is designed to act like a sponge: absorbing, storing, purifying and slowly releasing rainwater through green infrastructure — permeable pavements, rain gardens, wetlands, green roofs and restored waterways — rather than expelling it rapidly through pipes. China adopted the model nationally from 2015, targeting 70–80% of annual rainfall retained or reused on site, in response to chronic urban flooding and water scarcity; the concept parallels water-sensitive urban design and sustainable drainage systems (SuDS) elsewhere.
References
This reference provides supporting context for how “Sponge City” is defined and used.
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Overview
How it is used
The concept structures Chinese national urban policy, nature-based solutions programmes for flood adaptation, and the global uptake of blue-green infrastructure standards.
Why it matters
Sponge cities are the most ambitious state-backed experiment in living with water rather than fighting it — a template as urban flood risk grows.