How flood-prone Mumbai is tackling climate change, from underground tunnels to newer sewers

Like other store owners in their busy central Mumbai market, the Dadhia brothers have long kept the bottom shelf of their sari shop empty, having learned to live with the flooding that arrives every monsoon.

But next year's monsoon will be different, they hope.

A new underground water reservoir - constructed directly across from the sari shop and designed to stave off floods and store water - effectively guzzled down heavy rains that pummelled Mumbai on a recent day, shopkeepers said.

For once, shops in the Hindmata area were not full of stagnant water for 48 hours, they added.

"I don't think we will need to keep the lower shelves empty anymore from next year," Harish Dadhia told the Thomson Reuters Foundation, a tentative smile flitting across his face as he stood amid colourful saris pinned to the walls of his shop.

Low-lying Hindmata - a regular haunt of television news channels portraying "monsoon mayhem" - is becoming a test of the efficacy of solutions being launched to tackle more intense rainfall, warming seas and storms in India's financial capital.

Increasingly heavy rains in Mumbai have claimed more than 400 lives in the last decade, including in collapsed and flooded homes and as a result of over 170 landslides, civic data shows.

Officials in the city of 12 million hope changes like the new reservoirs can help curb that toll of losses and damage.

Mumbai is part of the C40 Cities network, a group of nearly 100 major cities globally working to drive faster action on climate change.

A view of a traffic jam on Marine Drive in Mumbai, India, September 8, 2021. Thomson Reuters Foundation/Niharika Kulkarni

Each has committed to delivering a climate action plan designed to spur uptake of clean energy, boost adaptation to climate threats and turn the 2015 Paris Agreement on climate change into an on-the-ground reality.

Mumbai launched its first Climate Action Plan (known as MCAP) this month. Amid dire predictions that large parts of the city could face inundation by 2050, it brings together different arms of the administration to try to fast-track solutions.

Other climate-smart measures include planting trees, improving solid waste management, boosting use of electric vehicles and installing charging stations.

But figuring out ways to address the city's worsening water challenges is a major focus, backers say.

The metropolis, set on the coast of the Arabian Sea, has recorded "extreme" rainfall - defined as more than 200 mm (7.9 inches) of precipitation in 24 hours - about a dozen times between 2017 and 2021, civic data shows.

That is double the number of such events for the previous five years, between 2011 and 2016.

For Mumbai's citizens, the heavier rains mean inconvenience and heartache: more frequent wading through flooded roads, deaths of loved ones and worsening losses for business and homes as civic workers struggle to pump out the monsoon floodwater.

Aaditya Thackeray, environment and climate change minister for Maharashtra - the Indian state that has Mumbai as its capital - said weather "anomalies" were no longer abnormal, and were a direct result of climate change.

Mumbai's annual monsoon period has shrunk from 120 to 70 days, he said, but the volume of rain has increased and is often now accompanied by gusty winds, creating worsening challenges.

"For climate change action, we don't have the luxury of time... we need to put it into fast-track action," Thackeray, who is also suburban Mumbai's "guardian minister", said in a statement to the Thomson Reuters Foundation.

The Municipal Corporation of Greater Mumbai, the city's civic body, has earmarked 3 billion rupees ($41 million) in annual spending to make its new climate plan a reality, with officials saying more will be allocated if needed.

So far the city has constructed three floodwater tanks offering a collective capacity of over 26 million litres, with plans to siphon the captured water into the sea during low tide, civic officials said.

Conservationist Subhajit Mukherjee, founder of nonprofit Mission Green Mumbai, also is overseeing the installation of an expected 6,000 rainwater harvesting pits in more than 1,000 municipal gardens, to recharge groundwater and check flooding.

Public posters coax citizens to "catch rainwater" by installing the pits - which cost up to 3,000 rupees ($40) and can hold 5,000 litres - in the open spaces of their apartment blocks.

More than 500 have been constructed in about 125 gardens since March, Mukherjee said.

The collected rainwater is intended to conserve municipal water supplies as the city's population and its temperatures rise, driving up demand for water, as well to help prevent flooding, he said.

Mumbai has not seen the serious water shortages faced in other Indian cities, with its seven rain-fed lakes that supply water largely keeping up with demand.

But some recent shortfalls in supply mean the city is also planning a costly desalination plant to convert sea water into drinking water, to be prepared for any shortages, officials said.

Mumbai's climate plan also aims to speed the introduction of electric vehicles to cut emissions and pollution.

Nearly 400 shiny red electric buses have now replaced about 20% of the civic transport body's diesel-run fleet, and the municipal corporation's own vehicles are next in line for an upgrade.

Mumbai authorities also hope to persuade residents to switch to electric vehicles, with a first public charging station installed last month and plans to offer tax concessions to electric vehicle owners.

But with much of the city's electricity still produced by coal - the most polluting fossil fuel - electric vehicles will not be climate-smart until the power grid also runs on clean energy, critics say.

Pradip Kalbar, a water and climate engineer and professor at the Indian Institute of Technology Bombay, said expanding use of electric vehicles was a good aim, not least to lower pollution.

But with the coal-fired power stations that supply Mumbai's electricity located in communities outside the city, a switch to electric vehicles and more power generation "will displace the pollution problem from Mumbai to another place", he noted.

For now, the "rate of improvement of the grid and the rate of introduction of electric vehicles are not matching", he said.

As the planet - and Mumbai - warm, the city is also facing another worry: cyclones.

The Arabian Sea is a particularly fast-warming part of the Indian Ocean, said climate scientist Roxy Mathew Koll.

"The Arabian Sea was cool and cyclone-shy, but we are seeing more cyclones with increased intensity and duration and chances of them coming close to the coast," said Koll, of the Pune-based Indian Institute of Tropical Meteorology.

Two cyclones neared Mumbai in 2020 and 2021 - something once rare and a particular worry in a city already struggling with flooding, he said.

"We often talk of cyclones and rainfall separately but we need to worry about multiple extremes overlapping," said Koll.

Emptying water into the sea from underground tanks, like the one at Hindmata, could be a challenge in high tide periods, with the water potentially making its way back onto land, experts warned.

City officials said such dangers were on their radar as they figured out how to manage new floodwater storage tanks.

"This is a new experiment... We are going cautiously and in a year's time we will get some feedback," said Suresh Kakani, additional commissioner with Mumbai's civic body.

In a report this year, the Intergovernmental Panel on Climate Change (IPCC), a body of top climate scientists, cited a study showing that annual flood losses in the world's 136 largest coastal cities could soar to $1 trillion by 2050, up from $6 billion today.

The report listed Mumbai among the cities with a population of over 10 million facing serious risk.

Consultant Advait Aundhkar worked on a 2019 study that estimated Mumbai had suffered 140 billion rupees ($1.9 billion) in flooding losses between 2005 and 2015.

Better measuring those losses, and planning to try to hold them down and keep the city running, will be crucial as climate change impacts strengthen, analysts said.

"We can't afford to have the city come to a standstill for three to four days every year," said Anjal Prakash, research director at the Bharti Institute of Public Policy at the Hyderabad-based Indian School of Business.

"Measuring losses is an important part of climate action. How will you plan or build if you don't know what the losses are?" asked Prakash, who is also an IPCC report author.

So far, Mumbai's disaster management unit has kept track of rain-related deaths.

But officials drafting the new climate plan said they hope to start combining data on losses of lives, property and other assets to help demonstrate the impact of work to make Mumbai more climate-resilient.

Pressure to act on mounting risks may soon come from new quarters, including residents of upscale south Mumbai, home to the city's stock exchange, iconic Marine Drive, consulates and the palatial residences of some of India's richest.

Last August, the area witnessed flooding for the first time in memory. Water inundated streets and parking lots and a landslide blocked an arterial road commonly used by lawmakers and business heads.

Sheetal Mehta, who lives on Bhulabhai Desai Road, home to millionaires, saw her building's parking lot flood.

This year, cyclone-driven rain and wind were so strong residents resorted to sealing their windows with duct tape to stop water seeping in and window panes from shattering, she said.

"To think the sea used to have a calming effect on me," said Mehta, who now worries about the area's future as flooding and cyclone threats grow.

Industrialist Jamshyd Godrej, head of the Confederation of Indian Industries' climate change committee and a south Mumbai resident, said last year's floods were a wakeup call for many like him more used to inundations hitting the city's suburbs.

Shopkeepers in Bhuleshwar, one of Mumbai's oldest markets in south Mumbai, also were shocked to find their shops flooded this year for the first time.

Cloth merchant Rajesh Mishra - used to keeping his bottom shelves stocked, unlike shop owners in flood-battered Hindmata - ended up dumping damp merchandise in July.

"When I saw my flooded shop, I couldn't speak. I didn't know how to react," he said. "I don't know what solution I have for next year."

Flood risks in Mumbai are compounded by its history of unplanned growth, with buildings and infrastructure projects having destroyed flood-slowing mangroves and reduced once wide river channels to constrained creeks.

Expansion of the city into the nearby seabed, on reclaimed land, also has been a problem, experts said.

The city's civic body is currently building a $1.7-billion, eight-lane coastal road to connect Mumbai's south and north and reduce road congestion.

The project includes India's first undersea road tunnel, an underground parking area for about 2,000 cars and a 125-acre garden on the reclaimed land, according to the civic body.

Backers say the road will cut commuting time and fuel consumption in a city rated as the world's second-most congested after Moscow, according to a traffic rating index of 400 cities.

"If environmental fears are real, so is our daily struggle. The coastal road will ease our commute. Taking my son for his 40-minute football matches and getting to work meetings takes me hours," said Tulika Bahl, 43, an information technology worker.

But critics said the project is at odds with creating a more climate-resilient city.

Hussain Indorewala, an assistant professor at the Kamla Raheja Vidyanidhi Institute for Architecture & Environmental Studies in Mumbai, said he believes worsening flooding in south Mumbai may be linked to the project and other construction.

Over the years, a business district has replaced mangroves, and a river was rerouted to accommodate airport expansion, Indorewala said.

"You have construction here, channelization (of rivers) there, mangrove destruction, changed land use - and that is causing more and more flooding," he said.

"Mumbai's problems are a combination of extreme weather events and poor planning," Indorewala added, terming the new climate action plan "theatre" if the potential flood impacts of projects like the new coastal road are not taken into account.

Civic officials said the coastal road - a project of Uddhav Thackeray, the chief minister of Maharashtra state and the father of environment minister Aaditya Thackeray - will include a sea wall of stone boulders to reduce storm water surges and the impact of rising sea levels.

Those who drafted the climate action plan said it was an evolving document and citizen input would remain critical. In September, the civic authority launched a public portal to solicit suggestions and opinions on the plan.

The strategy has steered away from conventional ways of tackling Mumbai's challenges of congestion and flooding, said Lubaina Rangwala, associate director of the World Resources Institute's Ross Center for Sustainable Cities, which drafted the document.

"The plan instead looks at prioritising walking, cycling, adding green cover and restoring wetlands and use of natural landscaping among other measures - instead of concrete embankments to address chronic flooding," she said.

The city has already taken steps to protect mangroves, wetlands and urban trees, she added.

In recent years it also has improved warning systems to alert citizens ahead of heavy rains, said civic official Kakani.

To make conversations about climate change more routine in government, Maharashtra state last December selected a group of "climate fellows" - aged 22 to 26 - who are pursuing degrees in environment, sustainability and policy fields.

They are now trying to build climate resilience by acting as a bridge between lawmakers, administrators and different branches of government, cutting jargon and working to make the discussion relevant to citizens, said Saurabh Punamiya-Jain, 26, who heads the group.

The fellows, for instance, helped carry out a cross-department greenhouse gas inventory that showed more than 70% of the city's climate-changing emissions come from energy, about 25% from transport and much of the rest from solid waste.

The price of rising flooding is already evident in homes like Munni Goud's.

The 45-year-old migrated to Mumbai 28 years ago, set up home in a tin shed near a water reservoir in the northern suburbs and began surviving on what her husband earned making sweet boxes at a local factory.

When her son reached working age better times seemed ahead, but a deluge in July 2019 - when up to 180 mm (7 inches) of rain fell in three hours - changed that.

Goud's family of six woke up to the "deafening sound" of the reservoir wall collapsing and floodwaters surging through the neighbourhood. Thirty people lost their lives - including Goud's 22-year-old son.

This year, with the reservoir wall still not rebuilt, Goud and other women from Ambedkar Nagar slum spent the monsoon season camping in a nearby open space, both to protect themselves from similar deluges and to demand alternate housing.

Minister Thackeray said the government was working to provide formal homes to all slum-dwellers within a decade's time to protect them from heavy rains and flooding.

Business heads said they fear worsening danger from floods could drive some of Mumbai's migrant workforce out of the city, as happened during the COVID-19 lockdown last year when tens of thousands left.

"What can cause people to leave Mumbai? If there is no livelihood and if there is no safety. We take talent for granted right now, but it will go down," predicted Anirban Ghosh, chief sustainability officer for the Mahindra Group, an autos-to-technology conglomerate.

But Mumbai's migrants say they have little prospect of jobs elsewhere - so their safety will depend on the city's actions to curb flooding.

"There is nothing in my village. Mumbai is my home. It is my only lifeline to livelihood," said Goud.