Mumbai floods every year during monsoon, but this year has been different

With ‘unprecedented’ being the mantra for 2020 events, the monsoon floods in India’s commercial capital, Mumbai, too, followed suit and reached areas that were never flooded before.

South Mumbai was lashed with its second-highest 24-hour rainfall since 1974 on August 5 and the city witnessed wind speed higher than what was recorded during Cyclone Nisarga, a tropical storm that hit the state in June.

Citizens and activists blame infrastructure work including the coastal road project and the Mumbai Metro project and highlight the need for long-term planning to address the impact of increasing extreme weather events in the city.

Prior to August 5, the national weather forecaster, India Meteorological Department, had issued a red alert for Mumbai and adjoining regions of Thane, Palghar and Raigad districts for August 4 and 5.

On August 5, Mumbai witnessed 294 millimetres rainfall in just 12 hours – the IMD categorises rainfall more than 204 mm (in 24 hours) as ‘extremely heavy’.

On August 6 morning, the IMD’s observatory in Colaba (Mumbai) had recorded 331.8 mm rainfall in 24 hours. This was not only the highest August rainfall since 1974 but also the second-highest 24-hour rainfall recorded by Colaba observatory in any month of monsoon since 1974.

Colaba observatory is representative of South Mumbai whereas the Santacruz observatory is representative of Mumbai. The other noteworthy characteristic of the August 5 weather was the wind speed was about 106 km/h which is more than 92 km/h recorded when Cyclone Nisarga skirted Mumbai in June.

The rainfall led to flooding in areas of south Mumbai such as Churchgate, Fort, Oval Maidan, Charni Road, Girgaum Chowpatty, Masjid station, JJ Hospital, Breach Candy, Haji Ali, Hindmata junction among others.

While the last location is prone to flooding every monsoon, the rest are never known to flood. Residents of south Mumbai, one of the original seven islands, have not experienced flooding even during the deluge of 2005 when Colaba observatory had recorded only 73.4 mm rainfall.

Atul Kumar, a member of Nariman Point Churchgate Citizens’ Association, said, “In this area, the flooding [on August 5] took everyone by surprise. Nobody could recall a time when there was so much rain, so much flooding and such high-intensity winds. Buildings on Marine Drive have been there since 1940 and despite being sea facing, this is the first time that we are seeing leakages in buildings. In the past also, Colaba has observed heavy rainfall but there has been no flooding. Some people say that the rain coincided with high tide but then it should have flooded in the past also.”

However, Kumar said there is no evidence to directly link the flooding to metro project work or coastal road project work.

The heavy rainfall coupled with intense winds led to around 600 complaints of trees or branches falling in Mumbai within three days (August 4 to 6).

They also led to the collapse of the iconic signage of the Bombay Stock Exchange, a landslide at Peddar Road, cracks at the Malabar Hill’s Ridge Road and cancellation of suburban trains. Hundreds had to be rescued from stranded trains using boats.

The IMD attributed the weather event to active monsoon conditions over the country’s west coast. Rainfall abated in Mumbai August 6 onwards but IMD has forecast another wet spell from August 11.

Natural, man-made factors

Activists and experts state that what caused the severity of floods this year was a combination of natural and man-made factors.

The South Mumbai area has seen work on two important infrastructure projects commence in recent years including the coastal road project and Metro phase-III. Both the projects, together worth billions of rupees, have been staunchly opposed by environmentalists for their ill-impact on local ecology.

Stalin D, director of a non-governmental organisation, Vanashakti, has been at the forefront of the Save Aarey movement, said the August 5 flooding was clearly due to these projects.

“If it were only due to heavy rainfall, how did these spots not flood in 2005? I had warned last year itself that Chowpatty will flood (owing to the coastal road work). When you reclaim the sea, the water has to go somewhere. Metro’s phase-III have also altered the underground drainage network,” he said.

In 2016, a report by the Council for Scientific and Industrial Research-National Institute of Oceanography had said that “the model simulations for the case of reclamation for the coastal road facility resulted in increased water levels, increased flow speeds and consequently increased bed level changes… However, the overall project of the coastal road needs to be planned and executed with minimum interference to the existing coastal environment.”

The CSIR-NIO report of 2016 was not commissioned to study the proposed coastal road exclusively but the impact of land reclamation and its influence on Mumbai’s coastline as well as its implications for proposed projects.

Activist Zoru Bhathena who has been vocal against both projects explained, “Historically, reclamation has proven bad for Mumbai which is why Cuffe Parade’s remaining reclamation was dropped, coastal road idea was also dropped after being conceived decades ago for the same reason. Besides, Metro authorities have dug up roads that had British-era stormwater drains underneath and such large scale digging affects groundwater retaining capacity. Metro phase-III have taken over so many open spaces as well that were available to absorb rainwater.”

Shweta Wagh, Assistant Professor at Mumbai-based Kamla Raheja Vidyanidhi Institute for Architecture and Environmental Studies, who had petitioned the Supreme Court against the coastal road, said, “Reclamation for the coastal road may be vacant but it is equivalent to concretisation.”

“Also, if you look at the profile of the intertidal area (affected by coastal road project), it retains seawater. Even though they say it is barren, it serves the ecological function of holding tidal water during high tide,” Wagh told Mongabay-India.

Role of concretisation

After facing criticism year after year for shoddy roads and footpaths, this year, Brihanmumbai Municipal Corporation has, in fact, increased the area under concrete. According to its budget for the ongoing financial year, 266 km worth of roads are proposed to be improved using concrete, which is nearly four times the 65-km in 2019-20, and 13 times the 20-km in 2018-19.

Besides, the civic body has started concretisation of footpaths using the likes of stencil concrete instead of paver blocks for better durability.

Bhathena told Mongabay-India that while tar roads allow 30% water to seep while paver blocks allow 50% water to seep underground, concretisation does not let any, leading to the entire volume of water running into the ill-equipped drains.

Nikhil Anand, a professor from the University of Pennsylvania criticised the municipal corporation over the flooding and rued about eco-systems which used to absorb extra water.

“With many of the city’s open spaces – playgrounds, intertidal regions – paved over, there is nowhere, but the city’s stormwater drains and rivers, for this water to go. The rivers have also been narrowed and channelised. After the 2005 floods, the stormwater drain capacity was upgraded in parts of the city under Brihanmumbai Storm Water Disposal System, a project to overhaul Mumbai’s water drainage system, from handling a maximum of 25 mm of rain to 50 mm of rain per hour. But this is their maximum capacity at low tide. The city needs to find other ways to accommodate rainwater when it falls. Unfortunately, the municipal corporation is doing the opposite by sanctioning real estate firms to pave over open space, or moving stormwater drains when they are on private land,” Anand told Mongabay-India.

However, urban planner Pankaj Joshi, director of Urban Design Research Institute, disagreed that concretisation of roads and footpaths caused large-scale flooding but instead emphasised on the hazardous concretisation of open space within housing societies compounds.

“It is time we create a 20-year climate change mitigation plan for Mumbai that will be linked to the city’s development plan and civic budget. Such extreme weather events are going to happen more frequently now and we need dedicated focus on mitigation,” said Joshi.

P Velrasu, who is the additional municipal commissioner and in-charge of the stormwater drain department, disagrees with activists.

“We don’t see any correlation between the two projects and flooding. The issue happened due to heavy rainfall and high-speed winds in the island city- the system cannot deal with that sort of downpour. Drainage systems can handle only 60-70 mm downpour. Concretisation happens in any developing city internationally. At other places, they have water holding ponds in their urban design. We also want to develop the same. What has been done in Japan is very expensive, instead, we can develop holding ponds under the city’s open spaces,” he said.

This article first appeared on Mongabay.