Rs 13,000 crore vs the monsoon: Mumbai civic body unveils flood mitigation plan

Flooded Andheri subway earlier this month. File pic/Atul Kamble

A permanent solution to flooding at the Andheri subway, 33 automated floodgates at outfalls to keep out tidal water, wider stormwater drains capable of handling up to 100-120 mm of rainfall per hour, restoration of mangroves and wetlands, and nature-based measures such as permeable footpaths and bioretention systems are among the key proposals in the Brihanmumbai Municipal Corporation's (BMC) Rs 13,000-crore Integrated Flood Mitigation Plan.

The plan combines large-scale engineering works with ecological interventions to strengthen Mumbai's resilience against flooding. mid-day had first reported in March that the BMC had submitted a Rs 10,000-crore flood mitigation and capacity-strengthening proposal to the National Disaster Management Authority (NDMA) under the Urban Flood Risk Management Programme (UFRMP), seeking financial assistance.

Engineering and ecological measures for permanent fix

According to Additional Municipal Commissioner Abhijit Bangar, who is in charge of the project, the plan focuses on both structural and nature-based interventions.

"We want to solve the Andheri subway flooding problem once and for all. Several interventions have also been planned for the Mithi River, which have been divided into flood management and river rejuvenation. Eighteen automated floodgates will be installed along the Mithi River to reduce tidal flooding, while automated floodgates will also be installed at coastal outfalls," Bangar said.

The civic body also plans to augment the carrying capacity of the city's stormwater drains. The proposal also includes underground water detention and infiltration tanks to temporarily store rainwater, along with unconventional flood-control measures such as permeable pavements, and bioretention systems to reduce surface runoff and improve groundwater recharge.

Why has the project cost gone up?

A senior civic official said the proposal initially submitted to the NDMA was worth a little over Rs 12,000 crore before the BMC revised it to Rs 10,000 crore. "The comprehensive flood mitigation master plan has now been pegged at Rs 13,000 crore. Of the total cost, 40 per cent will be funded by the NDMA, 30 per cent by the state government and 30 per cent by BMC," the official said.

Major structural interventions

Drain and nullah augmentation to improve water flow to pumping stations and natural water bodies
Rs 3087 crore

Mithi River flood mitigation and rejuvenation
Rs 1636 crore

Construction of Mahul and Mogra pumping stations
Rs 644 crore

Installation of automated floodgates at coastal outfalls
Rs 6228 crore

Upgradation of Haji Ali and Irla pumping stations
Rs 360 crore

Flood mitigation works at Andheri subway, including a pumping station
Rs 615 crore

Construction of embankments for flood protection and coastal resilience
Rs 308 crore

Nature-based interventions

Mangrove and wetland restoration
Rs 984 cr

Bioretention systems and bioswales for stormwater management and groundwater recharge
Rs 123 cr

Permeable pavements
Rs 251 cr

Urban parks and green corridors to improve flood resilience
Rs 396 cr

Project cost break-up (Rs 13,014 crore)

Component Allocation
Stormwater pumping stations and coastal resilience Rs 3639 cr
River rejuvenation, mangrove restoration Rs 2620 cr
Nature-based solutions Rs 1727 cr
Drain improvement, nullah augmentation and allied works Rs 4058 cr
Andheri subway flood mitigation Rs 615 cr
Technology-based early warning systems Rs 293 cr
Integrated planning, including Flood Risk Management Plan (FRMP), Blue-Green Infrastructure Plan and Flood Risk Zoning Rs 62 cr