Mumbai Rains: Waterlogging In the City Is A Man-Made Disaster

(As told to The Quint’s Ankita Sinha. This was first published on 6 July 2019. It's being reposted from The Quint's archives as Mumbai floods again during monsoon this year.)

Another monsoon, and Mumbai is inundated once again. Have you ever wondered how waterlogging became the unfortunate reality of India’s financial capital every year during Monsoon?

For over 300 years now, Mumbai has been receiving heavy rains and also witnessing high tides. The amount of rain that the city receives has remained the same. So, what has changed? Why does it now submerge the city after every spell?

Rapid urbanisation, which turned Mumbai into a concrete jungle, is one of the key reasons.

From A City of Lakes To A City Of Concrete

Most parts of Mumbai city is reclaimed. However, while the process of reclamation was carried out, low-lying areas like Hindmata in Parel, were not filled in adequately and continue to remain in the shape of a saucer, which causes water to accumulate due to heavy rains. (People have almost forgotten that Parel was where the governor lived because of it being one of the most beautiful parts of Mumbai.)

It’s hard to identifying the reason for overlooking this crucial feature. It could be due to lack of funds. 

As a result, these areas would always be prone to accumulation of water.

Another crucial factor that played a key role in deciding the topography of the city was indiscriminate industrialisation, finally leading to commercialisation. Especially the textile mills that dotted a large chunk of the city.

Even up to as recent as 10 years ago, Mumbai was home to at least 56 textile mills. The one feature that all the mills had in common was the water bodies within the lands, identified to house them. This was done in a bid to overcome the lack of piped water systems, when lands were acquired to house the mills.

But the problem began once the mills were commercialised after they went defunct, the ostensible excuse being the textile strike. The permits drawn up allowed even the lakes to be filled in. They faced the fate faced by natural water bodies like the Dhobi Talao and Mastan Talao, that once stored the surplus water that Mumbai received during rains, which were earlier filled up.

As a result, the excess water that used to accumulate in the lakes, water bodies, ponds, and streams, today comes onto the streets and reach Mumbai’s low-lying areas directly. 

Even if the authorities augment the stormwater drainage line to whatever extent now, indiscriminate urbanisation has already resulted in waterlogging of the streets, that would have otherwise never happened. Within the entire 603.4 sq km of Mumbai, water would percolate into at least 50 percent of the land and reach the water table. Now however, every single square foot is being used by builders for development.

There is no space left for percolation. As a result, water that would have otherwise seeped in underground, now comes back out onto the streets and causes flooding.

Implementing Long-Term Solutions

It’s still not too late to salvage the situation. There are planning principles through which one could go back and insist that the same principle of urban planning and practices known all over the world can be practiced even now.

For one, the authorities could insist on a compulsory green area of 20 to 25 percent, that’s connected to the ground rather than have a manicured garden.

This will help rain water percolate and take care of a major portion of the ground table recharging. This can be done even now.

Another solution could be to install inter and intra-connectivity of water channels running through the mills. This can aid in the flow of storm water. This can be done even today, but nobody wants to. There is no political will to implement the solutions as it is the builders who are in control, and whichever party comes to power, wants to be in their good books.

Stormwater Drainage System To The Rescue

Another temporary solution that could result in long-term benefits would be to ensure that the stormwater draining system is working at a 100 percent capacity.

Stormwater drains have been augmented, and the capacity to take away water is about 50 mm per hour.

If it rains more than 50 mm per hour, then in any case, there is no provision. This means, your stormwater drainage system must cater to more than 50 mm per hour, at least about 75-100 mm per hour.

If the drains, however, are not cleaned or desilted, then you can’t call it an accident. It is human error.

If the rain is within permissible limits for the stormwater drains to accept it, then there is no reason why there should be flooding.

For instance, if your capacity is to carry away 50 mm of rainfall per hour, then it should be able to carry 500 mm in 10 hours. In that case, if you receive 500 mm of rainfall in 10 hours, then there is no reason why it should flood. So, even if the water accumulates, if the stormwater drain is properly maintained, it will drain the water within 10-15 minutes. If it doesn't, then there’s a problem with the machines. If the rainfall per hour is more than what the stormwater drain can take, then within an hour or two, waterlogging should go away because you have a pumping system to take away the water.

Finally, they must ensure than the streets are not flooded, by implementing planning measures through which the streams, rivulets, estuaries and other natural water bodies, that would have drained in a natural manner, are recharged or reactivated, even if they have to be located below the ground. They could then be the natural reservoirs for surplus rain water.

All these factors put together, can form a comprehensive strategy to ensure that flooding is kept to a minimum, and even if water accumulates, it doesn't remain there for more than 10-15 minutes.

More Concretisation, More Waterlogging?

When you construct a transport system like the metro, you always need to consider that it will bring in extra water, and you must augment your water evacuation facility. They must be in tandem with each other. Any amount of concretisation would result in further pressure on the existing stormwater drain line.

The speedy implementation of the recommendations in the BRIMSTOWAD report, as well as those in the Chitale Committee and some in the Gadgil Committee report, will see a reversal of sorts, in what has been seen in the recent past as the ‘strangulation’ of the city.

In the case of the upcoming coastal road project, it is beyond what the size of the land is today, so that may not directly affect waterlogging. But, if they destroy the mangroves, then in the long term, the environment could suffer.

(The author, Chandrashekhar Prabhu, is an architect and urban planning expert who served as the President of the Maharashtra Housing and Area Development Authority (MHADA) between 1993-95 and was also the Chairperson of SEEPZ (Santacruz Electronic Export Processing Zone) in Mumbai from 1982-93. This is an opinion piece and the views expressed above are the author’s own. The Quint neither endorses nor is responsible for the same.)