Mumbai Under Water Again: Key Reasons Why City Keeps Flooding During Monsoon

Last Updated:May 27, 2025, 08:58 IST

Mumbai Rainfall: Mumbai has witnessed a significant shift in its rainfall patterns over recent years, posing a growing challenge.

Mumbai Rainfall: The Brihanmumbai Municipal Corporation (BMC) acknowledged that drainage cleaning operations were not yet completed.

Mumbai Rainfall: Mumbai is once again grappling with widespread waterlogging and disruption as the southwest monsoon arrived in the city 16 days early this year, setting a new record for its earliest onset in decades. The unseasonably early and intense downpour has brought familiar chaos to roads, railway tracks, and even recently inaugurated underground metro stations, raising critical questions about why the “Maximum City" continues to face flood-like situations with each heavy rainfall.

Why Mumbai’s Drainage System Makes Monsoon Tough For The City?

Mumbai’s drainage system operates in a delicate balance with the sea. Its efficiency is heavily reliant on tidal movements. During low tide, the city’s natural slope allows rainwater to drain relatively easily into the Arabian Sea. However, the situation becomes critical when heavy rainfall coincides with high tide. At these times, lock gates are employed to prevent seawater from rushing into the city. Even with the aid of pumping stations designed to expel collected water, the process is significantly slowed. The sheer volume of water accumulating in low-lying areas during high tide simply takes more time to clear.

How Does Mumbai’s Unique Topography Contribute To Flooding?

Mumbai’s very foundation contributes to its flooding woes. The city was originally comprised of seven distinct islands. Extensive land reclamation efforts over centuries joined these islands into a single, continuous landmass. While this allowed for massive urban development, it inadvertently created numerous low-lying areas. During intense downpours, rainwater naturally collects in these depressions. Despite a vast network of stormwater drains and pumping stations designed to manage this, the excess water accumulates before it can be effectively pumped out, leading to localized flooding.

Has Mumbai’s Rainfall Pattern Changed And Why Is That A Concern?

Yes, Mumbai has witnessed a significant shift in its rainfall patterns over recent years, posing a growing challenge. Instead of rainfall being spread out throughout the monsoon season, the city now frequently experiences intense downpours concentrated over much shorter periods. Even with built-in redundancies, the existing stormwater drains are often simply overwhelmed by these sudden, heavy deluges. This year, for instance, Mumbai has already broken a 107-year-old rainfall record for May, with the Colaba weather monitoring station recording an astounding 135.4 mm of rainfall in just 24 hours ending 8:30 am on Monday. The city’s total May rainfall of 295 mm has also surpassed the old record of 279.4 mm set in May 1918. Furthermore, the Southwest Monsoon advanced to Mumbai on May 27, a full 16 days earlier than its normal arrival date of June 11, marking the earliest monsoon onset over Mumbai between 2001-2025.

Is Critical Pre-Monsoon Work Unfinished This Year As Well?

The early arrival of the monsoon, as witnessed this year, presents a significant hurdle for Mumbai’s preparedness. Essential pre-monsoon tasks, such as the unclogging of drains and desilting operations, follow a fixed schedule. An early onset can disrupt this schedule, leading to incomplete work and leaving the drainage system functioning at less than optimal capacity.

Are Mumbai Floods A Failure of BMC Again?

The Brihanmumbai Municipal Corporation (BMC) acknowledged that drainage cleaning operations were not yet completed due to the monsoon’s early arrival, directly contributing to the flood-like situations observed. These pre-monsoon works are critical for the city’s flood resilience, and their interruption this year has created immediate challenges for authorities.

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News explainers Mumbai Under Water Again: Key Reasons Why City Keeps Flooding During Monsoon