Delhi caught unprepared yet again

In only a three-hour window between 2.30 am and 5.30 am, Delhi received 148.5mm, nearly three times that quantum.

Every monsoon, Delhi puts its hopes on desilting exercises and an aging drainage network that is based on 48-year old drainage master plan prepared in 1976 and capable of handling only around 50mm of rainfall in a 24-hour period. Any more and the city’s drains begin to overflow, submerging large parts of the city, throwing life out of gear.

A heavily waterlogged stretch at Tilak Bridge in south-east Delhi on Friday. (Sanjeev Verma/HT Photo)

In only a three-hour window between 2.30 am and 5.30 am, Delhi received 148.5mm, nearly three times that quantum. In 24 hours till 8:30 am Friday, that figure was 228.1mm, over four times what Delhi’s drains can handle, leaving large parts of the city knee-deep in water.

Despite tall claims of desilting exercises done before the monsoon season, Delhi is not likely to see any relief from its perennial waterlogging problem in the future either, unless it overhauls its decrepit drainage system and implements a new drainage master plan, government officials and experts said.

A government official said when the drainage master plan was prepared in 1976, it was done, keeping in mind the existing population of Delhi, which was only around six million. The plan was to help sustain the city for another two decades or so, before requiring change. Presently, Delhi’s population is over four times that, at around 25 million , as per the Master Plan Delhi 2021.

“The urbanised area has increased and the city has expanded. We also have seen more colonies come up and it is important that the drainage network expands with the growth seen. This has failed to take place and we still have the same drain as we had earlier,” the official added, asking not to be named.

Drains and roads in Delhi are managed by multiple agencies such as the Municipal Corporation of Delhi (MCD), the Public Works Department (PWD) and the National Highways Authority of India (NHAI) , with the Delhi High Court in April this year, calling for a single agency in Delhi to manage all its drains. PWD has now come forward to create a new master plan, but the maintenance work of Delhi’s 22 major outflow drains into the Yamuna is only expected to be taken over by Delhi’s Irrigation and Flood Control Department by next year.

Meanwhile, PWD said it had hired consultants to create this new plan and will focus on Delhi’s three large drainage basins -- Najafgarh , Trans-Yamuna and Barapullah .

“The consultant for the Najafgarh basin was appointed last year while those for the other two basins have been appointed earlier this month. These consultants have started conducting surveys and we have provided all the historical data we had. The plan may take about a year to get fully formulated,” a PWD official said, asking not to be named.

Overall, Delhi has nine different agencies overseeing 426.5km of natural drainage lines and 3,311.5km of engineered storm-water drains, and the multiplicity of agencies has often been blamed for the poor maintenance of the drainage network.

Spells of over 50mm in a single day are also becoming common, with multiple heavy rainfall days observed in 2021, 2022 and 2023. In 2021, Delhi recorded 1,512.4mm of rainfall till December 29, the second highest ever (behind 1,534.3mm in 1933). Last year in July, when similar scenes of massive waterlogging were seen, Delhi saw the monthly rainfall touch 384.6mm -- the third highest for July in the last 20 years as per India Meteorological Department (IMD) data, including 153mm of rain on July 8.

The new drainage master plan for Delhi was supposed to be created first in 2009, but kept getting delayed. In 2012, the Delhi government announced IIT Delhi would be creating a new drainage plan soon, but when the plan was eventually submitted in 2018, it was not implemented.

Sarvagya Srivastava, former PWD engineer-in-chief said the first step in fixing this yearly mess is to separate Delhi’s sewage system from the stormwater drains.

“Currently, unplanned disposal of waste leads to seepage of sewage into storm water drains which get blocked, leading to back-flow of water onto the streets every time the city receives even moderate levels of rain. We also need decentralised sewage treatment plants, which can reduce the need to transport sewage over large distances.”

Others said that the problem is also compounded by poor maintenance with even desilting drives, carried out by agencies ahead of the monsoon, merely being on paper.

“We have two problems. Our drains are unable to handle such a load, as they are old. At the same time, they are not being maintained at the level they should be, through the year. We also need to divert stormwater to water bodies wherever possible, as it is simply not possible to take Delhi’s entire drain network and empty it into the Yamuna,” said Diwan Singh, an environmental activist . Dr S Velmurugan, chief scientist and head of traffic engineering and safety division of Central Road Research Institute CRRI said the drainage capacity of storm water drains along the roads has to be an integral part of the road design when the roads are being developed and upgraded especially in the case of 1800 km of arterial and sub-arterial roads.

“It is unfortunate that the Capital is still operating on 1976 drainage masterplan which has outlived its utility. Agencies deploy pumps at hotspots but these are stop-gap measures which cannot be taken seriously especially when such extreme weather events are on rise,” he added.

Which means the only certainty in the Capital is that if it rains more than 50 mm a day, parts of the city will flood.