Every monsoon, Maharashtra faces a fresh set of challenges. Heavy rainfall often triggers landslides in hilly regions, disrupts highways and puts major infrastructure projects to the test.
This month, a monsoon-triggered landslide near Tunnel 2 disrupted traffic on the newly opened Mumbai-Pune Expressway Missing Link, highlighting how heavy rainfall affects infrastructure across Maharashtra.
But while landslides disrupt highways in the state's hilly regions, Mumbai battles a different monsoon challenge every year: urban flooding.
The city sees flooded roads, waterlogged neighbourhoods and railway disruptions during intense rainfall, especially in low-lying areas.
So, why does Mumbai continue to flood every monsoon?
Mumbai’s annual flooding problem is linked to three major factors: an ageing drainage network, low-lying geography and rapid urbanisation.
Mumbai’s Drainage System Is Older Than The Modern City
Mumbai’s stormwater drainage system dates back to the 1860s, when the city was much smaller.
The network was designed to carry rainwater through underground and surface drains before discharging it into the sea.
At that time, Mumbai had fewer buildings, lighter traffic and more open spaces. The drainage system was built according to the needs of that period.
Today, Mumbai has expanded rapidly. More buildings, roads and concrete surfaces have increased the volume of rainwater that must be managed during heavy rainfall.
The existing drainage network now faces pressure beyond what it was originally designed for.
During intense rainfall, drains often struggle to remove water quickly enough.
The situation becomes more difficult when heavy rain combines with high tides. Since Mumbai’s drains open into the sea, rising water levels can slow down the movement of rainwater.
Why A Few Hours Of Rain Can Flood Mumbai
Mumbai receives heavy rainfall during the monsoon, but the challenge is not only the amount of rain.
The intensity and duration of rainfall also play an important role.
When intense showers continue for a few hours, the drainage system struggles to handle the sudden increase in water.
Over time, many drains also accumulate silt, debris and, in some places, sewage, reducing their ability to carry rainwater efficiently.
This is why short spells of heavy rain can lead to flooded roads, railway disruptions and waterlogging across several parts of the city.
Mumbai’s Geography Makes Flooding More Likely
Mumbai’s location adds another layer to the problem.
Mumbai is a coastal city along the Arabian Sea and includes both elevated and low-lying areas and includes both elevated and low-lying areas.
Several parts of Mumbai were developed through land reclamation, where areas that were once under the sea were filled and converted into urban spaces.
These low-lying areas naturally collect rainwater, making places such as Andheri Subway and parts of Kurla more vulnerable during heavy rainfall.
Water tends to collect in these areas first and takes longer to drain away.
Concrete Has Reduced Natural Water Absorption
Urban development has changed the way Mumbai handles rainwater.
Earlier, open land allowed rainwater to seep into the ground. Today, large parts of the city are covered with buildings, roads and pavements.
This has reduced the city’s ability to absorb rainfall naturally and increased pressure on the drainage network.
As a result, a much larger share of Mumbai's rainwater now flows through drains instead of being absorbed into the ground.
Construction waste can also block stormwater drains, restricting the flow of water.
Rivers And Water Bodies Under Pressure
Mumbai’s rivers and waterways are part of the city’s natural drainage network.
However, pollution, sewage, industrial waste and encroachments have affected their ability to carry excess water efficiently.
The reduction of buffer spaces around water bodies has also increased flooding risks in nearby areas.
When heavy rainfall occurs, these waterways have limited capacity to manage the additional flow of water.
What Is The Government Doing To Reduce Flooding?
The Brihanmumbai Municipal Corporation (BMC) carries out annual pre-monsoon preparations, including cleaning and desilting stormwater drains to remove silt and waste.
These measures help improve water flow and reduce waterlogging during heavy rainfall.
The civic body also monitors drain-cleaning work and deploys dewatering pumps in flood-prone areas to remove excess water when drainage systems struggle.
Along with upgrading stormwater infrastructure, these steps aim to improve Mumbai’s ability to handle intense rainfall.
However, the city continues to face a long-term challenge, as much of its infrastructure now serves a far larger urban landscape than it was originally designed to support.
