Flooding is a chronic problem that threatens many Brazilian cities. In fact, this is not a local issue: in 2023, the world saw simultaneous flooding in Brazil, Greece, Hong Kong, Turkey and Bulgaria . Sponge cities are sustainable models that can overcome this problem. This model suggests rethinking the way water is currently treated in cities, where rainwater is collected directly into rivers . "The sponge city approach must consider the scale of water resources and environmental assets as quality of life attributes to rethink and transform cities," explains architect and urban planner specializing in sustainability Sergio Myssior. In addition to being a solution to flooding problems, sponge cities also contribute to improving several other environmental and even social problems, such as reducing pollution levels and creating recreational spaces and encouraging exchange between people.

What is a sponge city?

The concept of a sponge city is relatively new and is directly related to the Chinese architect, urban planner and landscaper Kongjian Yu , who led numerous projects on water absorption, creation of floodable parks and other instruments that later proved essential for the creation of one of the world's leading sponge cities, located in China. In 2012, Beijing suffered a flood that not only caused damage to the city, but also took the lives of more than 80 people. The following year, the Chinese national government launched the “ Sponge City Program ,” which encouraged cities to adopt green infrastructure (based on natural areas and water features ) instead of gray infrastructure (made of cement, concrete, steel, and asphalt ). Despite being something recent, the theoretical basis on which sponge cities are based rescues an ancient Chinese tradition. According to Kongjian Yu, "they are inspired by the ancient wisdom of agriculture and water management that uses simple tools to transform the global surface on a large scale and in a sustainable way."

How does a sponge city work in practice?

"Among them we can highlight linear parks, rain gardens, draining gardens, wetlands , draining floors and pavements, forced infiltration ditches, areas for water retention and delay, riparian forests, ecological corridors, urban gardens, green roofs , water reuse, among other elements", explains the urban planner.

Heat waves and sponge cities

Climate change is causing severe heat waves around the world. World leaders and the UN itself have expressed concern about this situation. For Sérgio, sponge cities can help reduce this discomfort. "When we analyze various indicators of Brazilian cities, especially in metropolitan regions, we notice a frequency of catastrophic events such as floods, landslides and disease vectors such as dengue, in addition to effects such as heat islands," he comments. The expert also highlights that social inequality corroborates this scenario, in which people in greater need end up seeing areas at risk of flooding as a housing option due to lack of options – and end up being, according to the architect, the most vulnerable to environmental problems.

In Brazil, do we have examples of sponge cities?

Several Brazilian cities are taking inspiration from the Chinese model to apply sponge city techniques, following the example of green infrastructure for a better quality of urban life . Belo Horizonte, São Paulo, Niterói are examples of regions that have adopted some techniques such as rain gardens, permeable areas, among others – but none of them are 100% sponge cities. "The big challenge is to integrate city and urban development policies with sustainability actions to create a virtuous cycle in the city. It's not about creating 'new cities', but rather taking advantage of their capacity to transform and regenerate . But for this to happen, action is needed from the public authorities, civil society, companies. All sectors are involved," explains the architect.