The heavy rain on Tuesday grinding Mumbai to a halt showed once again that the city’s defences against floods aren’t working. An outdated drainage system along with unplanned construction and receding mangroves lead to waterlogging every monsoon
‘Maximum City’ Mumbai was slowed down on Tuesday when the financial capital of India witnessed incessantly heavy rain, causing waterlogging on roads and trains coming to a halt.
As per reports, in nine hours on Tuesday, the India Meteorological Department (IMD) Santacruz observatory recorded 153.3 mm of rain, categorised as very heavy rainfall.
The weather bureau has also forecast the current surge in rainfall activity to continue in Mumbai and the entire Konkan region and ghat areas of Madhya Maharashtra till the end of this week. Maharashtra is very likely to experience an active rainfall spell this week.
The weatherman has also sounded off a yellow alert for Mumbai, with the National Disaster Response Force (NDRF) deploying five of its teams to the city on standby.
But what is it about Mumbai that it cannot handle the rain without getting choked almost every year during the monsoon season?
A closer look reveals that an outdated drainage system, destruction of the natural barriers against climate change and unsustainable urbanisation are among the chief reasons for the city drowning and unable to deal with heavy monsoons.
Location, location and location
Before delving into the issue of the outdated drainage system, one crucial aspect that contributes to waterlogging in the coastal city is the location of Mumbai itself.
A lot of Mumbai is actually reclaimed land. However, a lot of the filling hasn’t been done adequately and hence, there are several low-lying areas and some are quite high, which leads to some areas being saucer-shaped.
This means that when it rains — especially like on Tuesday — the water flows down into these saucer-shaped areas such as Sion, Andheri and Khar.
Drained out
Mumbai’s inability to drain out rainwater effectively is in part due to its old drainage system that cannot cope with the capacity of rainfall that the city witnesses on days like these.
The island city’s drainage system is 140 years old, designed by the British. At that time, most of Mumbai was green. The drainage system was designed considering that 50 per cent of rainwater will be going through drains and the rest will percolate into the ground water. However, today few parts in south Mumbai are open but the underground drainage system has remained the same.
A report by the Comptroller and Auditor General of India tabled in the state Assembly in 2019 revealed that the drains are heavily silted and punctured at many places.
In the suburbs of Mumbai, where millions live, there are roadside drains and the nullah system. Each year, hundreds of tonnes of garbage are chucked into these drains, choking them. Moreover, the nullah networks are often long and wind through congested localities before discharging into the sea. This affects the outfalls, meaning if it’s raining heavily, the drainage is slow.
Constructions and commercialisation
One of the primary reason for Mumbai’s chronic waterlogging woes is the frenetic pace of construction in the city. Mumbai is in a constant state of expansion, laterally and vertically, and large-scale construction activity is a constant for the city.
This impacts flooding in two ways: first, as more and more natural space gets converted into a built-up area, the natural ability of the land to absorb water and prevent it from collecting in a place is lost.
Second, the debris and waste generated by construction activity clog up the drains and nullahs, preventing the run-off water from escaping.
The Mumbai Metro, the coastal road, a new airport, the Mumbai-Ahmedabad bullet train project and a series of other road links are being developed to ensure that the city keeps moving. However, these projects, which aims to ensure that Mumbai never stops, is swallowing forests and affecting the coastline — which, in turn, will affect the drainage system and cause more waterlogging issues.
The Flood Preparedness Guidelines 2019 report by the Municipal Corporation of Greater Mumbai (MCGM) noted that the process of urbanisation played a major role aggravating the problem as it has caused significant alterations to hydrology, morphology, habitat and ecology of the city.
Cry me a river
Once upon a time, the rivers of Mumbai — Dahisar River, Mithi River, Poisar River and others — did the work of stormwater drains. However, illegal construction and dumping of garbage into them has curbed their capabilities.
According to a Mongabay report, “one of the major rivers, Mithi, has become a veritable sewer, choked with domestic and industrial waste and overflows every monsoon”.
Not only that, the wetlands along these rivers are now practically non-existent, which means that there is no buffer between the waterline and adjoining localities. When the rivers overflow, they automatically lead to flooding in such localities.
People wade through a water-logged street amid monsoon rains, near the closed Andheri Subway in Mumbai. PTI
Mumbai’s mangroves
Environmentalists have cited the loss of mangroves as one of the contributing factors to Mumbai’s flooding issue.
City-based environmentalist Debi Goenka explained that mangroves absorb excess water but they are being destroyed in Mumbai in the guise of infrastructure development.
Speaking to PTI, he was quoted as saying, “Destruction of mangroves has definitely been one of the major causes of flooding, since the land reclaimed from mangroves is now blocking the rain water from flowing out into the sea. The capacity of mangroves to absorb flood water has also reduced,” he said.
Other issues
Besides the above problems, there are also issues that also contribute to the waterlogging issue.
Mumbai boasts of 2,100 hectares of salt pans, which act as buffers for tide and heavy rainfall. However, these have not been deemed as wetlands and over 15 per cent of the salt pan cover has been opened up for construction of affordable housing.
Environmentalist Stalin D of NGO Vanashakti in a Mongabay report said, “Saltpans are the lowest-lying areas of the city. If you start converting them into concrete, first the chances of floods will go up and then entire saltpans will be grabbed by land sharks who get the rules bent in their favour.”
Declining tree cover, which also impacts flooding, is another reason for Mumbai’s monsoon misery.
If these issues aren’t looked at, it seems Mumbai’s waterlogging woes will continue, putting communities at risk and forcing Mumbaikars to grapple with extreme flooding.
With inputs from agencies
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