Urban stormwater management has become an urgent issue driven by population growth, rapid urbanization, changing land use and climate change. To meet this challenge and curb the surge of floods, the sponge city concept brings together nature-based solutions, low-impact development, best management practices, sustainable drainage systems, water-sensitive urban design, green cities and blue infrastructure. The sponge city idea is already being put into practice in Spain and elsewhere.
Main idea: lessen the impacts of dense development by mimicking natural processes and delivering broader wins such as improved biodiversity, comfort and reduced heat in cities.
These systems feature green spaces, porous paving, green roofs, private roof retention, artificial wetlands, cisterns for rain storage and absorbent paving to replace traditional street concrete. They aim to slow runoff, capture rain where it falls, and reuse water wherever possible.
An international scientific study published in WIREs Water discusses the potential of these initiatives to address urban flooding and lists key elements for success. The authors note that in 2015 the Chinese State Council launched pilot projects in 30 cities to explore sponge city concepts.
The goal is for these cities to absorb about 80 percent of surface runoff and to reuse at least 70 percent of collected rainwater by 2030. The project has since expanded to more cities and regions.
Nature-based solutions emerged as a sustainable approach for urban stormwater management and flood risk reduction, according to the study’s introduction.
social transformation
Despite the promise, the authors acknowledge limits to how much rain urban areas can absorb. Sponge cities are not a universal fix for flooding. They emphasize that community-based measures form an essential piece of a broader response, and the development framework must advance toward flood-resilient cities.
La Marjal floodplain park in Alicante illustrates how green spaces can support flood resilience and biodiversity through integrated water management. Suez is linked to these initiatives as a practitioner in water systems.
“Building flood resistance does not mean only investing in grey-green-blue infrastructure; it also requires a social transformation toward flood-resilient communities,” researchers suggest.
“Sponge cities” represent a paradigm shift in sustainable water management by weaving blue-green systems with traditional gray infrastructure. The idea champions a responsive approach to water, rather than simply trying to push it away.
Historically, floods were managed by conveying water through pipes or by reinforcing banks with concrete to prevent overflow. A sponge city, by contrast, absorbs rain and slows runoff. It starts with water-retentive features such as ponds and permeable landscapes, then uses meandering streams and wetlands to gently slow flow while creating green spaces, parks and habitats for wildlife. This approach also helps purify runoff through natural processes and reduces pollutants.
Green roofs and permeable pavements
The 2018 United Nations World Water Development Report highlighted the benefits of sponge city approaches. It notes that nature-based solutions, including urban wetlands restoration, green roofs, permeable pavements and bioremediation, can lessen the adverse effects of rapid urbanization on natural ecosystems.
Regional examples include rain gardens and biological retention systems used to collect runoff, remove pollutants, and store some water for drought periods, supporting irrigation and cleaning needs.
The sponge city initiative remains a focal point for the Region of Murcia in addressing extreme precipitation and flooding. Sustainable Urban Drainage Systems (SUDS) in coastal municipalities are among the most common strategies, with multiple projects compiled by the Nature-Based Solutions Observatory, an organization coordinated by a foundation and a global conservation body.
Two pilot projects are planned to launch soon, aiming to apply sustainable drainage system chains in San Javier and Cartagena. Successful Spanish examples include the El Marjal floodplain park in Alicante, Vitoria’s Green Belt, Alcorques Vivos in Barcelona and the Iberum Central Platform in Toledo.
Reference work: WIREs Water (note: cited study provides broader context for sponge city outcomes) [citation attribution].
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