Why a few hours of rain still bring India's biggest cities to a standstill

Business Standard

27-05-2025

On Monday morning (May 26), commuters on Mumbai's much-hyped Aqua Line 3 metro were met not by the promise of smoother travel, but by ankle-deep floodwater. The newly inaugurated underground station at Worli was inundated after an intense burst of monsoon rain, water poured down its walls, flooded the platform, and leaked through the roof. The city's earliest monsoon arrival in 35 years had made its entrance, and left the latest civic showpiece in tatters.
Meanwhile, in Delhi, Saturday's record-breaking downpour turned the capital's roads into rivers. With 185.9 mm of rainfall this May, nearly nine times the usual, the city is witnessing its wettest May ever. Flights were delayed, traffic choked, and low-lying areas submerged as thunderclouds ripped across the skyline.
Down south, Bengaluru, last week, was battered by a 12-hour rain marathon that flooded 500 homes, killed at least three people, and filled over 20 lakes to capacity. The city, perched on a plateau with no natural river drainage, turned into a bowl of chaos, yet again.
From north to south, the script is the same: a few hours of rain and entire cities collapse. Why do Indian cities flood so easily? Why haven't years of warnings, policies, and crores in spending fixed this? And more importantly, who is really accountable? People are left stuck, governments rush to react, and the damage runs deeper than just flooded roads—it hits lives, livelihoods, and the economy.
Why are cities like Bengaluru, Delhi and Mumbai so flood-prone?
Much of urban India relies on colonial-era drainage systems designed over a century ago. Take Mumbai: the city's stormwater network, laid out by the British in the 1860s, was engineered to carry 25 mm of rain per hour during low tide. That might have sufficed for a coastal town of 2 million people—not for a mega-metropolis of over 20 million that now routinely sees rainfall exceeding 100 mm/hour.
In Delhi, the drainage network was built for just 50 mm of daily rain, based on standards from 1976. The capital, however, now regularly receives four times that amount in a single day. Bengaluru's stormwater drains are equally archaic and poorly maintained, clogged with silt, debris and sometimes even furniture.
The result then is that rainwater that should drain away instead turns city streets into cesspools.
How poor planning and lost wetlands made urban flooding worse
Rapid and unplanned urbanisation has only made things worse, argue infra experts. Across cities, construction has bulldozed through natural buffers like lakes, wetlands and drainage valleys.
Mumbai has lost nearly 80 per cent of its natural water bodies over the last four decades. So has Bengaluru, where once-interconnected lakes like Bellandur and Varthur are now flanked by tech parks and apartment blocks. In Delhi-NCR, high-rise colonies and malls stand where floodplains once soaked up excess rainwater.
These wetlands acted like sponges. With them gone, there is nowhere for the water to go, except up into homes and down into basements.
Even where drains exist, they often serve as dumping grounds rather than water channels. Solid waste, silt and construction debris routinely clog drainage lines, reducing their capacity by as much as 40–60 per cent.
Mumbai, for instance, produces over 9,000 tonnes of garbage every day. Much of it ends up in the city's waterways. In 2025, despite a ₹550 crore desilting budget, only 37 per cent of the silt in the Mithi River was removed before the rains began. Court delays were blamed. The consequences were predictable.
In Bengaluru, experts estimate that only 10 per cent of the city's stormwater drain capacity is functional. The rest is filled with solid waste, sewage or hardened silt.
Why flood-control budgets don't solve India's waterlogging problem
Infrastructure breakdowns are only part of the story. At the heart of the waterlogging crisis lies broken urban governance.
Drainage systems fall under a patchwork of agencies, municipal corporations, state departments and central bodies, each working in silos, often at cross-purposes. In Mumbai, the long-delayed BRIMSTOWAD project, launched in 1993 to modernise stormwater drains—its Phase II remains just 50 per cent complete, while Phase I is at 75 per cent completion. Disputes between the BMC and state authorities have stalled key pumping stations for years.
Delhi's new drainage master plan has been in the works since 2016 but remains unapproved. In its absence, the city continues to combine sewage and stormwater in the same pipes—a recipe for disaster when it floods.
How topography and encroachment magnify urban flood damage
Topography plays a cruel trick on Indian cities. Many of the worst-hit areas are built on reclaimed or low-lying land, where water naturally collects.
Mumbai's plush neighbourhoods like Worli and Nariman Point are built on reclaimed land. When it rains, water from higher parts of the city rushes down to these pockets, often blocked by construction or tidal backflow.
In Delhi, the Yamuna floodplains have been encroached upon by both formal and informal settlements. During intense rains, these areas are the first to drown, and the last to receive relief.
Is climate change accelerating urban flooding in Indian cities?
Climate change has turbocharged these vulnerabilities. Extreme rainfall events are now more frequent, intense and unpredictable.
Mumbai received 944 mm of rain in a single day in 2005, a record many dismissed as a freak event. But by 2024, such 'freak' events are becoming annual. Climate models predict a 30 per cent increase in extreme rainfall by 2030. Delhi saw over 200 mm of rainfall in 24 hours in 2024. Bengaluru, too, has faced cloudbursts that its outdated infrastructure simply cannot handle.
When heavy rains coincide with high tide or construction blockages, the system collapses, and the city drowns.
Who is responsible when floods claim lives and paralyse cities?
The toll is not just infrastructural, it's human. In 2024, Mumbai recorded at least seven deaths from open manholes and submerged drains. Delhi saw the death of nearly 20 people last year, mostly children and workers, to drowning or electrocution. In May 2025, Bengaluru saw three flood-related deaths, including a child and a 63-year-old man electrocuted while trying to drain his home.
The economic losses are equally staggering. Flood-related disruptions in Mumbai alone have cost the city thousands of crores over the years, with halted trains, shuttered offices and damaged infrastructure.
Meanwhile, authorities continue to offer reactive, band-aid solutions: temporary dewatering pumps, emergency desilting drives or new bylaws for rainwater harvesting. But without long-term, integrated planning, these remain cosmetic fixes.
Upgrading city-wide drainage systems requires multi-agency coordination, consistent funding and data-driven design based on updated rainfall and runoff patterns, none of which urban India currently has in place.
As the climate crisis intensifies, the water will only rise. The real question then becomes how long can Indian cities tread water before they sink under the weight of their own neglect?