On 26 July 2005, Mumbai was brought to a sudden standstill by what the weather records called a ‘once-in-a-century cloudburst.’ In less than 24 hours, the city received over 900 mm of rain – nearly 40 inches of water. Local trains stopped by mid afternoon, traffic gridlocked entire suburbs, and low lying areas like Dharavi and the Bandra Kurla Complex were under water. Schools and workplaces shut down, flights were grounded as runways flooded, and over 1,100 lives were lost in accidents, electrocutions, wall collapses, landslides and post-flood infections.
The deluge exposed deep vulnerabilities: a century old drainage system designed for just 25 mm of rain per hour, blocked stormwater networks, shrinking mangroves, disappearing wetlands, and the steady spread of concrete where open land and floodplains used to be.
The Mithi River had become little more than a sewage drain, and large-scale land reclamation along creeks and ports had closed off the city’s natural drainage pathways.
In the aftermath, a fact finding committee laid out recommendations that led to the Disaster Management Act of 2005 and the creation of the National Disaster Management Authority. The BMC launched the BRIMSTOWAD project to overhaul drainage, and built pumping stations and widened rivers like the Mithi and Dahisar.
Efforts were made to map flood zones, install early warning systems and conduct public awareness campaigns. Around ₹1,000 crore was disbursed to Mumbai under a special ₹1,200 crore urban flood management fund.
Two decades later, some progress is visible, but the underlying challenges remain. As recently as 2024, parts of Mumbai still experienced waterlogging after short, intense spells of rain.
The drainage upgrade remains incomplete, with several pumping stations running below capacity. Encroachments persist, and the city continues to lose open space and green cover to construction. The scale of rainfall may now be more frequent than earlier thought – what was once considered a hundred-year event is becoming more common.
Pattern Repeats In Fast-Expanding Cities
The pattern repeats itself in fast-expanding cities too. Gurugram, for instance, has seen even moderate rain bring large stretches – Sohna Road, Hero Honda Chowk, Golf Course Extension, Cyber Hub – to a standstill. In 2023 and 2024, several areas saw waterlogging after just 100–130 mm of rain in a few hours.
Stormwater drains built decades ago have not kept pace with the rapid vertical and horizontal expansion of the city. Underpasses flood quickly when pumps fail or switch on too late. Missing links in drainage between private and public areas exacerbate the issue, especially in older residential zones.
Aravalli hills Pushes Water Into Urban Basins
Gurugram’s natural geography also works against it. A bowl-shaped topography drains water from the Aravalli hills straight into built-up urban basins. In the past 40 years, Gurugram has lost nearly half of its natural water bodies and wetlands, while canals and nullahs have been concretised or have simply vanished during real estate booms.
A 2024 audit revealed that nearly half the city’s storm drains were either clogged or poorly maintained. Experts estimated annual flood-related economic losses at ₹150 – 200 crore.
To its credit, the city has begun taking action. Over the last year, modular rainwater harvesting systems have been introduced in parks and green belts, with the capacity to store up to two lakh litres per site – far more than older soak pits.
Ward councillors are advocating for pre-monsoon drain cleaning to commence earlier and be more closely monitored. Canopy covers are being installed in ramp areas, and several underpasses now feature sensor-triggered pump backups.
Similar Conditions in Bengaluru, Hyderabad, Lucknow…
Following a similar trajectory, cities like Bengaluru, Hyderabad, Chennai, Pune, Lucknow, Bhopal, and even Goa have faced flood-like situations due to intense rainfall, blocked drainage systems, or rapid urbanisation choking natural water channels.
Hyderabad’s financial district and Bengaluru’s tech corridors have both seen office evacuations and crores in damages, as commercial and residential zones are built over lakes, tanks, and wetlands.
What World Bank’s Report Says?
Recognising the scale of the crisis, recent global and national reports have called for long-term solutions. The World Bank’s 2024 report on urban resilience for Indian cities places a strong emphasis on climate-sensitive master plans, integrated drainage and solid waste systems, and investing in natural buffers such as wetlands and floodplains. It also calls for better coordination between municipal bodies, state authorities, and developers – an area that remains fragmented in most states.
Sponge Cities – Need of an Hour
The World Economic Forum, in its recent guidance for emerging economies, has promoted the idea of ‘sponge cities’ – urban environments that absorb and reuse rainwater through permeable surfaces, green roofs, blue-green corridors, and wetland conservation.
Some Indian cities, such as Bhubaneswar and Surat, have started experimenting with these principles, albeit in pilot phases. Bengaluru, too, is experimenting with nature-based sponge city models, though unevenly.
In terms of numbers, an earlier World Bank estimate had pegged India’s urban resilience investment needs at over $840 billion by 2030 – including roads, drainage, water, and housing. Without this, the costs of inaction – lost productivity, public health crises, and flood recovery – are projected to rise sharply in the coming decades.
Some of the best lessons are coming from cities that started early.
Kolkata, for instance, has consistently invested in preserving its wetlands and upgrading drainage infrastructure over the past 15 years. The result: a sharp drop in flood intensity and duration, even during heavy spells.
In 2025, India committed nearly $300 million to a new urban resilience fund, aimed at helping cities such as Mumbai, Chennai, Ahmedabad, and Gurugram restore water bodies, modernise flood response systems, and improve drainage.
Two Decades After Mumbai Floods
The 2005 Mumbai floods served as a wake-up call, leading to significant structural reforms. But the more profound lesson wasn’t just about infrastructure – it was about respecting the land and its natural rhythms.
Two decades later, that lesson is more urgent than ever. Climate change is making extreme weather more frequent, but urban planning hasn’t kept up. The focus must now shift to long-term resilience, which involves protecting wetlands, reopening storm channels, utilising permeable surfaces, and recharging groundwater. For cities already living on the edge of disruption, that could be the difference between recovery and collapse.
