Waterlogging at King’s Circle towards Sion hospital after heavy rain in Mumbai on Monday, July 1, 2019 | Photo Credit: The Hindu
When the rain comes, the flood follows. Natural flood is understandable but the artificial flood in every town every year is naturally a question of concern. Every year, for a week or so, Mumbai is in the news for waterlogging that causes a lot of inconveniences to people of the city. The media starts blaming the Shiv Sena who is in charge of the municipal corporation and the BJP state government for lack of preparedness in tackling such a situation. Many are questioning the insufficient drainage condition, corruption, and apathy of the state government. I don’t dispute all that. But then, there are certain things we must realise before blaming anybody for such artificial inundation.
First, if there will be heavy rain, artificial flooding and waterlogging are unavoidable. This not only happens in Mumbai but in most cities in India and across the Globe. If you search on google for flooding in any big cities, for example, California, USA you will find pictures of floods not very different from Mumbai or any other city. Similarly, you can check for Toronto, Canada, Sidney, Australia, or even Tokyo, Japan. No matter how well planned a city is temporary flooding during heavy rains cannot be avoided. You can’t provide bigger drains to drain out the rain water to make a city dry immediately.
Let me give you a simple example based on mathematical logic. Let there be a 6m wide road. Both side houses cover 15 meters each. That means per metre length the surface area is (15+6+15) is 36 Sqm. Now let’s have rainfall of 8 inches in a couple of hours. Let’s allow this water to flow in the entire six meters width of the road. What would be the height? It would be [(36 X 0.2)/6] = 1.2-meter height. Now if you consider drain width, then what would be its height? Let’s have a 1 m width drain? What would be its height? It would be (1.2X6/1) = 7.2 M height. Is it possible?
The above calculation is for simple illustration to understand why there will be temporary flooding. You can’t provide drains of such size which will eat up your road and even your houses for heavy rains for a few days in a year. Thus, temporary flooding is natural and normal for any city.
The real issue is the duration of this temporary flooding. Here, the administration has an important role to play. They must ensure that the entire drainage system is clear and various receiving channels have enough capacity to hold the runoff water. For example, if there are four drains connected to one drain, the size of each drain must be enough so that drainage will be faster or within a stipulated period. If those channels are not enough then the drainage of water will take more time. That’s the only difference between developed countries who are able to clear the temporary flooding quickly and Indian cities. Thus, I am not sparing the departments in charge but we should consider all the facts before assigning blame.
Let me give you another example. When I was executing six lanning of NH-16 from Bhubaneswar to Cuttack, I was informed by Cuttack Collector that one of the underpasses was flooded up to a height of around 1.2 meters. I was really surprised. There was no chance of water coming from any other places except its defined catchment which is very small. Then I did my job very sincerely in providing a proper drainage facility. Even in high-intensity rain, the temporary flooding should not be more than six inches and the duration of drainage after the rain stops shouldn’t be more than half an hour. But the rain had stopped for more than six hours yet traffic was closed. Everybody was angry with me.
I inspected the place and found that the drain to the exit channel was clogged by paper-plates. People after eating fast food threw the paper plates in the side drain which finally blocked the exit of the water. The municipality has provided a dustbin there, but people didn’t use it. I engaged people to clear the face of the exit channel and within fifteen minutes, there was no water on the underpass.
The point is simple. We have the habit of throwing things into the side drains. Even an alert municipal body can’t clean all the drains simultaneously, thus such littering finally clogs the waterway at some point resulting in a long duration of water-logging.
It’s easy to blame authorities for every problems and inconvenience. But we must have civic sense. If we don’t do our duties as citizens in a city, then we are sure to face the music. The rainy-season woes in Mumbai, Chennai or any other city will continue until we learn our civic duties. We must be aware that throwing our waste into the storm-water drains will lead to blockages. Then there are encroachments all the time. If encroachments will increase the drainage passages will reduce, resulting in the delay of water discharge.
The above is not to exonerate municipality authorities. They are definitely responsible for mismanagement. But then, we are equally responsible for not doing our civic duties, which results in our cities turning into water parks every year.
Note: The author is a professional civil engineer with more than thirty years of experience.