The first spell of monsoon rain caught Brihanmumbai Municipal Corporation completely off-guard on Monday. As Mumbai witnessed the earliest onset of monsoon in its history, bringing the city to a near halt, the rains led to inundation of low-lying areas like King’s Circle to locations like Hindmata and Gandhi Market for several hours early in the morning and afternoon. While the deadline for the BMC to complete all pre-monsoon preparations that includes essential infrastructure works such as road repairs, drain cleaning, and flood mitigation efforts is the first week of June, the early onset of rains caught the authorities, IMD and Mumbaikars off-guard. Sources said that the Monday’s mayhem was largely a result of incomplete pre-monsoon work undertaken by BMC–desilting of drains and rivers and installation of dewatering pumps–and that led to issues of waterlogging and other related problems across the city. Besides, sources in the civic authority claim that the concretisation of dug up roads that were targeted till arrival of monsoon, also could not be completed.

While the civic officials maintained that they were on schedule with the pre-monsoon preparedness, they added that the advance onset was the primary reason behind flash floods in Mumbai on Monday. The BMC in its 2024-25 budget had allocated Rs 3,000 crore to the storm water drains (SWD) department which is responsible for mitigating and tackling waterlogging in Mumbai.

Heavy rainfall has led to traffic congestion in multiple locations in the city. (Express Photo by Sankhadeep Banerjee) Heavy rainfall has led to traffic congestion in multiple locations in the city. (Express Photo by Sankhadeep Banerjee)

Non-functional dewatering pumps

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As part of its pre-monsoon preparedness, the BMC was in the process of installing 482 dewatering pumps in multiple low-lying areas in Mumbai. Sources say that a large number of these pumps that run on electricity and have a capacity to channel out 60 cubic meters to 1,000 cubic meters of water every hour, could not be operationalised in-time and led to issues of waterlogging in the city.

“The process of connecting these pumps with a generator usually takes place during the last week of May. This year, we didn’t get any dry patch as the pre-monsoon showers lashed last week, soon after which the monsoon onset began. These pumps run on high voltage electricity and to connect them to generators in a flood like situation (as today) would have been extremely risky,” an official told The Indian Express.

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These pumps are placed on key flood-prone areas like Sion, Antop Hill, Dadar, Mahim, Andheri–that have a record of consistent waterlogging. After placing these pumps on their specific locations, they are connected with high-powered generators which enables their operation.

The official said they were given a deadline of June 5 to complete all the pre-monsoon work. However, this year, monsoon onset happened almost 15 days ahead of schedule in Mumbai, much ahead of the normal monsoon onset between June 7 and 11.

In Mumbai’s Matunga on Monday. (Express photo by Ganesh Shirsekar) In Mumbai’s Matunga on Monday. (Express photo by Ganesh Shirsekar)

Civic officials said that at Hindmata, all the seven pumps that BMC had set up were non-operational on Monday morning. Furthermore, the officials also maintained that at Gandhi Market, six pumps were non-operational. Together these pumps have a capacity to channel out 3,000 cubic metres of water every hour. In 2023, the BMC declared these two spots as ‘flood free’ after installing these high-power pumps stating that these places will not record any waterlogging in the near future.

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“In Hindmata and Gandhi Market, the pumps were totally non-operational that led to flooding within a short period of time. In King’s Circle and Sion also, the dewatering pumps were not operational. These pumps became active post 12 pm following which water started to dissipate. We installed pumps at Khar and Andheri subways as well, following which water stopped accumulating there,” the official said.

Incomplete desilting work

A key factor behind the flash floods in Mumbai was the non-completion of desilting of drains. The process of desilting refers to the removal of silt, muck and sediments which get deposited on the beds of the water bodies. These sediments slow the pace of water flow, which in-turn results in overflowing of water and thus causing water-logging after heavy rainfall.

Every year, the BMC appoints multiple contractors to desilt these drains as a preventive measure against waterlogging during the monsoon as the city has a vast network of drains of nearly 3,800 km–almost double the network of roads.

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This year, the BMC had appointed 25 different agencies in a two-year contract amounting to Rs 468 crore to carry out desilting work in Mumbai. However, the civic body’s data show that till date, the BMC has been able to achieve 71% of the pre-monsoon desilting work. That means, out of 9.61 lakh metric tonnes (MT) of total silt, nearly 6.88 lakh or 71.5% of silt has been removed.

Furthermore the civic body’s data shows that the island city, which recorded the highest quantum of waterlogging throughout the day, had the lowest progress of desilting. The civic body’s dashboard shows that out of 30,281 MT silt, around 22,178 MT or 73.24% was removed till date. Meanwhile, in the western suburbs, around 1.97 lakh MT or 95.07% of the total 2.06 lakh MT was removed, while in the eastern suburbs, around 1.11 lakh MT or 91.27% of the 1.22 lakh MT was removed by the authorities.

The dashboard further shows that the Mithi river has seen a 53% progress of desilting works with 1.13 lakh MT of silt removed out of 2.14 lakh MT of silt.

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“Since desilting was not completed in full scale, the rain water couldn’t pass smoothly through the drains and water channels. As a result, they got overflown on the road. We were given a June 7 deadline to complete the desilting work on the basis of which manpower and machinery were deployed,” said an official.

“Places like Nariman Point, Grant Road recorded over 200 mm of rainfall within a few hours. This added up to the woes because there was no outlet for the rainfall to pass. Therefore, the entire belt of the island city got waterlogged. Alongside the rain water, there was also an issue of floating waste which mainly comprises plastic waste that clogs the drains,” the official said.

Roads dug up for concretisation

BMC had, in its budget 2025-26, announced that 2,118 roads having a total length of 701 km have been taken up for concretisation in two phases and said that nearly 1,233 roads will be completed by June 2025. In a report published on April 6, the Indian Express had stated that nearly 525 km of roads were dug up in Mumbai for the ongoing concretising works. Speaking to The Indian Express, a senior civic official said that out of the total roads that were dug up, nearly 350 km have already been concretised.

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However, when contacted, Abhijit Bangar–additional municipal commissioner (Projects) said that while a total of 1,174 roads were dug up till the time monsoon had arrived for concretisation work, 1,164 roads have been entirely concretised by now.

“We had clearly maintained that no new roads will be concretised post May 20. So, there was no new road left where we had to lay concrete when the rains came. All the roads that were incomplete were in the curing period of the laid concrete blocks. Therefore, in a way, the road concretisation works are under control and didn’t suffer much damage,” Bangar told the Indian Express.

“More than 90% of the roads that were taken up for concretising were completed. The remaining roads which we couldn’t complete will be asphalted. According to the status of work that was done till today, the overall portion of roads that need to be asphalted now stand at less than 10%,” Bangar added.