Why Delhi roads get flooded every monsoon?

Professor Emeritus of IIT Delhi talks about how a drainage master plan, if implemented, could have offered a lasting solution

Updated - October 16, 2021 05:29 pm IST

Published - October 04, 2021 01:41 am IST - New Delhi

A DTC bus stuck on Minto Road following a heavy spell of rain.

A DTC bus stuck on Minto Road following a heavy spell of rain.


During the monsoon, many parts of Delhi, including arterial roads, get waterlogged leading to traffic snarls even with an hour’s rainfall. The main reason is the problems related to the city’s storm water drains. The city works on a drainage master plan made in 1976 and one such plan prepared by IIT Delhi for the Delhi government in 2018 is yet to be implemented. In an interview with The Hindu, Professor Emeritus of IIT Delhi, A.K. Gosain, whose team prepared the new plan, tells how the story of a new master plan turned out to be one of disappointment.

Why does Delhi face urban flooding?

In Delhi’s case, flooding could be due to two reasons: floods in the Yamuna or local rainfall. In 1978, Delhi had witnessed a flood due to a rise in the Yamuna water level. But the annual urban flooding we see is due to local rainfall. The run-off water (water left after being absorbed by the earth) from the local rainfall is supposed to drain into the Yamuna through storm water drains. But due to a combination of reasons, including sewage flowing in storm water drains, it does not properly drain into the Yamuna and leads to urban flooding. The drains were made decades ago to handle a particular amount of run-off water. Over the years, the paved area has increased due to development. So, if earlier, a particular amount of rainfall generated 50% of run-off water and the rest was absorbed by the earth, now the run-off water is about 90%. Also, due to climate change, the intensity of rainfall has increased and this also increases the amount of water. But the drainage system is the same and it is unable to handle the excess water.


Is Delhi’s natural topography a reason for urban flooding?

West Delhi is at a higher altitude and there is a slope towards the Yamuna and this actually aids water to drain into the Yamuna. If a city’s topography is flat, then it will be more prone to urban flooding. So, compared to Kolkata or Patna, Delhi is at an advantage in terms of topography. But the part of the city east of the Yamuna is a low-lying area.

How did IIT Delhi start working on Delhi’s drainage master plan?

In 2012, I was heading the civil engineering department at IIT Delhi and used to have meetings with the government on different issues. It was during one such meeting that the then secretary of the Irrigation Department of the Delhi government told me that they were trying to get a drainage master plan made for the city. The government had floated tenders and private companies were asking for ₹10-₹11 crore. We said that we could create a simulation model for the whole Delhi. This would be a framework that the government could upgrade and keep using. We submitted a proposal and agreed to do it for ₹80 lakh, which was less than 10% of what the private companies had quoted.

What is the master plan and why is it needed?

A master plan is needed to study why flooding is happening even with light rain and come up with a plan to fix it. We used data provided by departments ranging from soil type, topography and land use to rainfall and existing storm water drain network to create a mathematical model (a software), which can generate solutions for waterlogging for the whole city. We generated four solutions for different drains — adjusting slope of the existing drain, diverting water to existing water bodies, using additional storages, and other development works. These solutions considered the rainfall, slope of the drain, and many other factors and were done with a bigger picture in mind to provide a comprehensive solution to the city, rather than isolated ones. The model is a dynamic one and can be used to even assess the impact even constructing new drains. The model will keep on giving solutions as you change the different parameters. That is the beauty of the model we have created. Rather than giving the work to a contractor without knowing the impact, the government can actually assess the impact of proposed changes.

The master plan was commissioned in 2012, but why did it get delayed?

The government was supposed to give us data of the drains and we were told that the data was digitised. But we were shocked when we saw the data. In the name of digitisation of drains, there was only a line showing that a drain was passing through an area. The size, depth, slope etc., which are needed for analysis, were not there. We immediately sought a meeting with the Chief Secretary and said that nothing could be done with this data. He understood the issue and directed 11 departments, under whose jurisdiction the drains fall, to provide us with data of the drains. These departments in turn engaged contractors to give the data.

What happened after that?

It took more than a year to get the data. But there were problems in that too. We kept on telling them that in many segments the data given to us showed that the drain was going up instead of down. We call them adverse slopes. A drain needs a gradual slope for water to flow through it of its own under gravity. So, an adverse slope means that either the data is wrong or the construction of the drain in that area is problematic. We kept on asking the departments to verify the data; some did it, but majority of them did not verify the data given to us. We even sent 900 students over the course of four-five years to observe the condition of the drains. They had clicked about 2,500 geo-tagged photos of the drains. These photos showed that the drains were full of muck, which went against the government’s claim of cleaning them.

When did you submit the report?

We submitted the draft report in December 2016 and then the departments kept correcting the data and we submitted it again in April 2017, May 2017, November 2017, and the final report was submitted in July 2018. We mentioned in the report also that the data was not verified by the departments. As part of the report, we gave them suggestions to divert water coming to the drains by digging rainwater harvesting pits in parks and diverting water to water bodies. We also told them that we could help them with how to remove silt in drains and verify it. These were things that could be done right away, but they didn’t do anything.

Was it implemented?

On August 1, 2018, we gave a presentation to Chief Minister Arvind Kejriwal on the master plan. The CM asked different departments to implement the recommendations made in the report and we thought that the project was over from our side. But nothing happened after that. A technical expert committee was formed in 2012 to be involved with us from the beginning on the project, but it had never met with us. In 2019, suddenly, it met for the first time and it was decided that the departments should verify at least 10% of the data. Again, the departments were not responding and after a lot of pressure, in 2021, some departments said that of the 10% data, there was 50% error — it took two years for this. Now we are disappointed and feeling very foolish that we decided to help the government. Many people will say that the project didn’t work because IIT didn’t do its job.

Can the master plan be implemented in the current form?

No, the study has to be reworked with validated data. The best way forward will be to identify the perpetually flooded areas and identify drainage networks belonging to those locations. The data of these networks should be verified on priority and the rest can be taken step by step. Since we have provided them the complete modelling framework, the government should close this phase and discuss the way forward as a separate project.

So, is the project over now?

No, the project is not concluded. After nine years, we haven’t been given even one third of the agreed payment. More than two months ago, we had written to the government to end the current project, but there has been no reply from them.

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