Analysis: Why Same Areas In Mumbai Get Submerged Every Monsoon

As heavy rain lashed Mumbai this week, videos of waterlogged roads, stranded vehicles and flooded subways once again dominated social media. In Sion, water accumulated in low-lying stretches. Subways in parts of the city reported flooding. Traffic slowed, trains faced delays, and residents in vulnerable neighbourhoods found themselves confronting a problem that has become all too familiar.

The issue has triggered questions regarding why some parts of the city continue to flood year after year despite decades of studies, infrastructure projects, desilting drives and monsoon preparedness plans.

For many Mumbai residents, the city's flood map has become remarkably predictable.

Areas such as Hindmata in Dadar, the Andheri and Milan subways, parts of Sion, Kurla and several low-lying pockets near the Mithi River repeatedly feature in monsoon advisories and news reports. These are not newly discovered vulnerable locations. They have been identified as flood-prone for years, sometimes decades.

Following the devastating floods of July 2005, when over 900 mm of rain fell within 24 hours, and hundreds lost their lives across the Mumbai Metropolitan Region, authorities launched a series of initiatives aimed at improving the city's resilience. Stormwater drainage upgrades, pumping stations, flood-warning systems, desilting programmes and infrastructure redesigns were all intended to reduce the impact of future flooding.

Yet many of the same hotspots continue to experience severe waterlogging.

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Better Prepared, Yet Still Vulnerable

To say that nothing has changed would be inaccurate.

Mumbai today is better prepared than it was two decades ago. The city has expanded its pumping infrastructure, introduced more sophisticated weather forecasting systems and established emergency response protocols that allow authorities to react more quickly to extreme weather events.

Researchers studying urban flooding have also found evidence that mitigation measures have reduced flooding intensity in some locations.

However, preparedness and resilience are not the same thing.

The recurring appearance of the same flood-prone areas suggests that while authorities may have improved their ability to respond to flooding, they have not fully eliminated the underlying vulnerabilities that cause it.

Why These Areas Keep Flooding

One reason is geography.

Many of Mumbai's chronic hotspots are low-lying areas where rainwater naturally accumulates. During periods of intense rainfall, particularly when high tide coincides with heavy rain, the city's drainage network struggles to discharge water into the sea. Water that would normally drain away instead backs up into roads, subways and residential neighbourhoods.

The city's rapid urbanisation has compounded this challenge. Over the years, open spaces that once absorbed rainwater have been replaced with concrete surfaces, reducing the ground's ability to naturally absorb excess water.

In some locations, engineering solutions themselves face limitations. Subways, by design, sit below surrounding road levels. During cloudbursts or prolonged rainfall, they effectively become collection points for water. Authorities have repeatedly installed pumps and drainage systems, but some locations continue to flood whenever rainfall exceeds design capacity.

The Mithi River Factor

For areas such as Kurla and neighbourhoods near the Mithi River, flooding is linked not only to rainfall but also to the condition of the river and associated drainage channels.

Questions on desilting, encroachments and the river's carrying capacity emerge almost every monsoon season. While authorities undertake pre-monsoon desilting exercises annually, concerns persist about whether these efforts are sufficient to cope with increasingly intense rainfall events.

The problem becomes particularly acute when heavy rain coincides with high tides, reducing the ability of rivers and drains to discharge water efficiently.

Climate Change Is Changing The Equation

A growing body of research suggests that Mumbai's flood challenge can no longer be understood solely through the lens of infrastructure maintenance.

Climate scientists have repeatedly warned that extreme rainfall events are becoming more frequent and more intense.

Infrastructure designed decades ago may not have been built to handle the volume and intensity of rainfall that cities are experiencing today.

This creates a moving target for planners. Even when drainage systems are upgraded, changing rainfall patterns can quickly reduce the effectiveness of those improvements.

The result is that areas that historically flooded continue to do so, while newer parts of the city are increasingly experiencing waterlogging as well.

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The Cost Of Recurring Flooding

The consequences extend far beyond traffic disruptions.

Research examining excess mortality associated with monsoon flooding in Mumbai estimated that heavy rainfall contributes to thousands of additional deaths over time through drowning, electrocution, disease outbreaks and the worsening of existing health conditions.

The economic costs are equally significant. Businesses lose working hours, transport networks slow down, schools shut, deliveries are disrupted, and public infrastructure suffers repeated damage.

Flooding is often measured in terms of submerged roads and disrupted transport, but its true cost is much higher. Researchers at the University of Chicago estimate that extreme monsoon rainfall contributes to between 2,300 and 2,700 deaths in Mumbai each year.

The economic value of these lives lost has been estimated at roughly Rs 10,000 crore annually. And that figure does not include the wider costs of flooding, from damaged infrastructure and lost wages to healthcare burdens and disruptions to daily life across the city.

For residents of chronic flood hotspots, these costs are not occasional inconveniences. They are annual realities.

The Unanswered Question

Every monsoon brings a familiar cycle.

Heavy rain arrives. The same locations begin to fill with water. Emergency teams deploy pumps. Traffic diversions are announced. Residents wait for the water to recede.

Then the rain stops, the water drains away, and attention shifts elsewhere until the next monsoon.

Mumbai's flooding problem is often framed as a challenge posed by extreme weather. But the persistence of the same vulnerable locations suggests a deeper issue.

The consequences of recurring flooding extend far beyond traffic disruptions and waterlogged roads. A recent study by researchers at the University of Chicago found that extreme monsoon rainfall accounts for roughly 8% of all deaths in Mumbai each year.

The study also highlighted the unequal burden of flooding, noting that nearly 80% of those who die during frequent flood events, particularly when heavy rainfall coincides with high tides, live in the city's slum settlements, The findings underscore how Mumbai's flood crisis is not merely an infrastructure challenge, but also a public health and social equity issue, with the worst impacts often falling on the city's most vulnerable residents.

Two decades after the 2005 floods, the city's preparedness may have improved. Yet the recurring appearance of Hindmata, Sion, Kurla and several subway corridors on annual flood advisories raises a difficult question for planners and policymakers.

If these hotspots have been known for years, why do they remain hotspots at all?

Until that question is answered, Mumbai's flood map is likely to remain one of the most predictable things about its monsoon.