Mumbai civic body's flood control plan targets stormwater drains, avoids widespread road digging

The Andheri subway, which was closed at least 10 times in July 2025 due to waterlogging. File pic/Satej Shinde

Part of the Brihanmumbai Municipal Corporation's (BMC) flood-mitigation plan for Mumbai involves increasing the carrying capacity of underground stormwater drains, involving digging up newly concreted roads across the city. At present, 95 per cent of Mumbai's over 2000 km underground drain network has been enhanced to a carrying capacity of 55 mm of rainfall per hour, from 25 mm, as per the recommendations of the Chitale Committee report following the 2005 deluge in Mumbai.

In January 2023, BMC finalised its Rs 17,000-crore plan to concrete 692 km of Mumbai's roads. To avoid digging newly concreted stretches, the civic body plans to replace drains only where there is no other option to abate waterlogging. "Sites will be selected after careful study, and drains will be augmented only where required. However, all infrastructure development work that is necessary is an ongoing process for a city like Mumbai," said Additional Municipal Commissioner Abhijit Bangar.

2023
Year BMC finalised plan to concrete 692 km of roads

How BMC plans to avoid unnecessary digging

. Not every existing drain will be replaced with one with a higher carrying capacity
. A study will be conducted about flooding patterns, topography of landscapes, and the requirements of areas
. Sites will be selected where drain augmentation is the only solution to tackle waterlogging
. The study will be conducted with experts from IIT-Bombay

Andheri subway Why does it get flooded?

. Due to the gradient of the low-lying area, water flows towards the underpass at high velocity
. This is the catchment area of the Mogra nullah, which makes a 90-degree turn at one point
. Even the dry weather flow (amount of water flowing through drains during the non-monsoon period) under the Andheri subway is high, equating to 15 to 20 mm of rainfall. This is why even with rainfall as low as 40 mm, the subway gets flooded

What solutions are the BMC exploring?

The BMC is considering constructing holding ponds at a cost of approximately R600 crore. This will give relief for rainfall up to 75 mm per hour, with a net impact of 55 mm of rainfall, due to the dry weather flow

What options were put on hold?

Turning the nullah northward and then westward, at the juncture where it turns 90 degrees. However, this would give relief for only about 55 mm of rainfall per hour. Considering the dry weather flow, the net relief would be hardly more than 30 mm of rainfall, at a cost of Rs 250 crore