Indian cities have grown by replacing wetlands, lakes, and open spaces with impermeable surfaces like asphalt and concrete. The result? Rainwater has nowhere to go except overloaded drains. According to a 2021 study by the Central Pollution Control Board (CPCB), India has lost more than 30% of its wetlands in the last three decades, many to urban encroachment. Without natural buffers, even moderate rainfall can cause flash floods.

The Sponge City Concept

Originating in China in 2014, the Sponge City model focuses on integrating nature-based solutions into urban planning. Instead of draining water away as quickly as possible, sponge cities slow down, absorb, filter, and store water for later use. Techniques include green roofs, permeable pavements, rain gardens, and restored wetlands.

Lessons from India’s Flood-Prone Cities

Chennai’s Pallikaranai Marsh: Once sprawling over 50 sq km, it now covers less than a tenth of its original size due to encroachment. Restoration efforts have shown that even partial wetland revival can improve water retention and groundwater recharge.

Mumbai’s Mithi River: Encroachment and debris dumping have reduced its capacity, contributing to the catastrophic 2005 floods. The Brihanmumbai Municipal Corporation (BMC) has since initiated desilting and mangrove protection measures, but more is needed.

Guwahati: Integrated rainwater harvesting in select public buildings has reduced localised flooding while providing a supplementary water source.

Key Actions for Indian Cities

Urban Wetland Restoration – Protect and revive existing lakes, ponds, and marshes through legal safeguards and community stewardship.

Permeable Infrastructure – Replace conventional pavements with permeable materials to allow water infiltration.

Green Roofs & Vertical Gardens – Reduce runoff while improving air quality and lowering urban heat.

Decentralised Rainwater Harvesting – Mandate rooftop harvesting in all buildings above a certain size.

Integrated Flood & Water Management – Use GIS-based mapping to plan drainage and storage in harmony.

Why This Matters Now

The IPCC warns that extreme rainfall events in South Asia will become more frequent and intense by mid-century. Cities like Surat and Kolkata are already experiencing rain events exceeding historical intensities, overwhelming existing drainage. Sponge city principles provide a climate-resilient, cost-effective way forward—turning floods from a crisis into an asset.

Final Thought

A sponge city is not just an engineering project—it is an urban philosophy. It recognises that water is both a threat and a resource, and that our cities must adapt to coexist with it. The choice is clear: either keep battling floods year after year, or reimagine urban India as a network of living, breathing sponges.