Sponge Cities (Geography)
Sponge Cities (Geography)Why In News:With Indian cities facing recurrent monsoon flooding, attention has turned to the 'sponge city' concept, a nature-based approach to urban water management that seeks to make cities absorb, store and reuse rainwater rather than simply channelling it away through drains.Source: The Indian Express, Page 10, 7 July 2026 - 'How to absorb rain: What cities must learn'What is a Sponge City?The concept was developed by Chinese architect Kongjian Yu, and China began implementing it in 30 pilot cities from 2014, aiming to convert 80% of its urban areas into sponge cities.Sponge cities rely on Nature-based Solutions (NbS) such as permeable pavements, green roofs, rain gardens, bioswales, restored wetlands and urban lakes to retain water at its source, slow runoff and allow groundwater recharge.The approach draws on the principles of Low Impact Development (LID) and Sustainable Urban Drainage Systems (SUDS), which mimic natural hydrological processes instead of relying solely on grey infrastructure like storm drains and pumps.Relevance to Indian CitiesRapid concretisation, encroachment on natural drains, and the loss of lakes and wetlands in cities such as Mumbai, Bengaluru and Chennai have reduced their natural capacity to absorb excess rainwater, worsening flood risk.Pilot efforts are underway in cities like Chennai, where 'sponge parks' use blue-green infrastructure to manage a large share of stormwater runoff and reduce urban heat, and in Mumbai, where restoring mangroves, salt pans and natural drainage channels has been proposed to make the city more flood-resilient.Key Facts for PrelimsThe IPCC's Sixth Assessment Report warns of more intense storms and flooding events as global warming intensifies, making urban flood resilience an increasingly important adaptation priority.India's urban population is projected to reach around 600 million by 2036, intensifying pressure on existing drainage infrastructure.Nature-based flood solutions have been found to be more cost-effective than conventional grey infrastructure, with global studies estimating natural approaches can be about 50% more affordable while adding greater ecological value.