Delhi is yet to update the drainage master plan that was designed in 1976. Then lieutenant governor Tejender Khanna in 2009 asked the civic agencies to prepare a new master plan. But no progress was made. The first credible attempt to update the plan was initiated by the Aam Aadmi Party government in 2021 with the appointment of the Public Works Department as the nodal agency. In 2022, the Delhi government announced the appointment of two consultants but efforts are yet to translate into gains on the ground even as the city continues to battle waterlogging.

However, a new drainage master plan will take over a year to materialise and its implementation was unlikely before the monsoon of 2025. PWD, in May this year, finally appointed a consultant to make the master plan for Delhi’s Najafgarh basin, the largest of the three basins, apart from Barapullah and Trans-Yamuna. The consultant has been given one year to complete the project.

Meanwhile, last month, bids were also floated to appoint consultants for the other two basins, which were cancelled because only one consultant had applied. The department is expected to float a new tender in about 10 days and consultants for the other two basins are likely to be finalised within the next few months.

“Even for Najafgarh, the consultant will make a detailed plan over the next nine months. Based on their recommendations, we will check the feasibility and prepare estimates, which will then be sent to the government for approval before work begins. Meanwhile, if there are smaller, local suggestions, we’ll try to implement those along the way,” said a senior PWD official, requesting anonymity.

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Delhi can be primarily divided into three large drainage basins — Najafgarh, Trans-Yamuna, and Barapullah. According to estimates by PWD, the city’s old drainage system can cater to a maximum of 50mm of rainfall and anything over it overwhelms the system resulting in flooding of arterial roads and subsequent traffic congestion.

On days with heavy rainfall like Saturday and Sunday, the gaps in the water removal capacity get exposed. Several such heavy rainfall days with over 50mm of rainfall were observed in the last two years.

On Saturday, Delhi recorded 126.1mm of rainfall till early evening, while a cumulative rainfall of 153mm was recorded from 8.30am on Saturday to 8.30am on Sunday. This was already three times the amount of rainfall that Delhi’s existing drainage network is designed to handle.

Officials said that when the master plan was last prepared in 1976, Delhi’s population was around 6 million. However, according to the draft of the Master Plan of Delhi 2021, Delhi’s estimated population is around 25 million and the total urbanised area is likely to be around 920 sq km.

“With changing geographical and demographic conditions over the years, it is important to upgrade and modify the drainage network accordingly so that it can handle the discharge in the current situation. Over the years, there have also been changes to the system, local interventions for solutions at some places, and blockage and encroachment at other places. All these need to be looked at and solutions have to be implemented,” said a second PWD official.

Officials added that the irrigation and flood control department has already conducted the initial topographical surveys and other studies. The consultant has to now use these to come up with viable and implementable action points.

While the drainage master plan process will take much longer, the department said that it has taken corrective steps in terms of capacity enhancement and engineering solutions on 13 critical waterlogging points like Minto Road, Pul Prahladpur underpass, and WHO underpass at ITO, which used to get frequently flooded.

Several waterlogging hotspots are being monitored through 24-hour CCTV cameras. The hotspots that will be on the PWD’s watchlist this season are New Rohtak Road-Anand Parbat and Adhchini, which have been added this year, along with Pul Prahladpur underpass, under Zakhira flyover, Loni Road roundabout, Jahangirpuri Metro Station Road and the Karala-Kanjhawala Road.

“All underpasses will get flooded briefly during heavy rains as these are low-lying areas, but the drains are holding up well, despite such heavy rain. We have made special arrangements and are frequently getting pumps replaced in the problem areas,” said the second official.

Interventions that have been done at the other hotspots include the development of a drainage system and the construction of a sump at New Rohtak Road-Anand Parbat, enhancing the pumping capacity, and installation of screens to arrest garbage falling from railway land under Zakhira flyover, additional pumps and a sump near Loni Road roundabout, cleaning of drain from Azadpur to Mukarba Chowk and installation of a permanent pump at Sanjay Enclave to clear Jahangirpuri Metro Station Road, repair of Karala-Kanjhawala Road and remodeling of the drain along it, and the remodeling of a drain at Adhchini.

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Experts said that a city’s stormwater system plays a critical role in mitigating urban flooding. “While developing storm water master plan for an existing city it is imperative to take cognisance of existing ground situation, in-depth understanding of peak rainfall data along with intensity as well as geological understanding. The stormwater master plan should facilitate techniques that aid ground water recharge, recycling and reuse of storm water as well as preserving the natural ecosystems such as water bodies, riparian corridors, etc. The plan may consider including strategies for upcoming or greenfield areas in specific,” said Prerna Mehta, associate programme director, WRI India.