Delhi, Deluge, Drainage: Here Are The Details

Delhi has been severely affected by continuous rainfall for two consecutive days, causing significant disruptions as the city’s drainage system remained overwhelmed to handle excessive rainfall this season.

Various areas of the city, including parks, parking lots, underpasses, markets, schools and hospitals, were all submerged along with continuous chaos on the roads.

Images and videos circulating on social media depict commuters wading through knee-deep water — highlighting concerns regarding the effectiveness of the city's drainage infrastructure.

Despite claims made by the Public Works Department (PWD) of better monsoon preparedness this year, the reality has proven otherwise, as the national capital experienced higher-than-expected rainfall resulting in extensive waterlogging throughout the city.  

According to multiple reports, over the last two days, PWD's flood control room received around 100 flooding complaints, while the Municipal Corporation of Delhi (MCD) and New Delhi Municipal Council (NDMC) received 26 and 24 complaints respectively.  

In 36 hours starting 8.30 am on Saturday, Delhi recorded an unprecedented 260 mm of rainfall — prompting the government to issue a flood warning and shut schools for a day.

In a 24-hour period ending at 8.30 am on Sunday, the Safdarjung Observatory, Delhi's main weather station, recorded 153 mm of rain.

This marked the highest rainfall for a single day since 25 July 1982, when 169.9 mm of rain was recorded.

Other weather stations at Ridge, Lodhi Road, and Delhi University recorded 134.5 mm, 123.4 mm, and 118 mm of precipitation respectively within the same 24-hour period.

Additionally, Lodhi Road and Ridge witnessed further rainfall of 116.1 mm and 65 mm between 8.30 am and 5.30 pm on Sunday.

Government data reveals that Delhi has experienced more than 20 per cent of its entire season's rainfall in a single day.

Record-Breaking Rainfall For Waterlogging Crisis

"Due to this high intensity rain within a short span, all main drainage barrels were full and discharged rainwater more than their capacity. Because of this, excess rainwater was flown back over the roads mainly at Panchkuian Road, Connaught Place, AIIMS flyover and other places," said NDMC in a statement.

As heavy showers resulted in familiar scenes of waterlogged roads and stranded vehicles, residents expressed their frustration with Delhi's inadequate drainage system.

The city has 201 natural drains which can be divided into three main drainage basins: Najafgarh, Trans-Yamuna and Barapullah.

However, due to continuous urban growth and significant changes in land use, various parts of Delhi face recurring flooding issues.

These problems are exacerbated by factors such as excessive surface concreting, disappearance of water bodies, encroachments on stormwater drains, and the discharge of untreated sewage and waste, which obstruct the natural flow of water.

Additionally, the management of the drainage system involves multiple agencies, further complicating the situation.

All these factors underscore the urgent requirement for a revamp of the city’s drainage system to adequately cope with such "unprecedented" rainfall.

The last drainage master plan for Delhi was created in 1976. PWD estimates that the old drainage system can accommodate a maximum of 50 mm of rainfall. Anything exceeding this threshold overwhelms the system, leading to the flooding of major roads.

Hence, during periods of heavy rainfall, these limitations in the water removal capacity become evident.

In the past two days, Delhi received rainfall that was three times the capacity of the existing drainage network.

State Government’s Preparedness For The Monsoons

The Delhi government recently provided an account of the measures it had taken since the previous monsoon season.

In preparation, the government claims that it invested significant time and resources in addressing waterlogging issues at key locations throughout the city.

Since February 2023, the Delhi government undertook the desilting of drains citywide — which involved the removal of loose and hardened silt from drains to restore their optimal functioning.

Delhi Mayor Shelly Oberoi had stated in June that this desilting process would be completed by 15 June, reported Business Standard.  

However, in a house meeting on 9 June, the civic body’s engineering wing had announced that just 55 per cent of the corporation’s 700 bigger drains had been cleaned till then. The initial deadline for completing desilting of drains was not met.

Thereafter, The MCD announced on 20 June that 80 per cent of small drains had been desilted, with the goal of completing all drains by 28 June. The statement also revealed that only about 68 per cent of the work to remove silt from major drains had been completed.

In addition to this, the mayor said that permanent and temporary water pumps should be installed at places prone to waterlogging, and sensitive places should be monitored through CCTV cameras.

The Delhi Jal Board (DJB) issued its annual monsoon preparedness guidelines, including a flood control order effective from 27 June. Officials were instructed to closely monitor 41 vulnerable waterlogging points.

The DJB emphasised to regularly inspect the equipment installed at these locations and removing any obstructions that impede rainwater flow into drains during the monsoon season.

However, reports indicated that at Zakhira, a waterlogging hotspot, pumps frequently got stuck due to floating material. Multiple pumps were replaced, allowing water drainage and reopening of the underpass only after an eight-hour closure.

A City That Reports Waterlogging Year After Year, Is Yet To Upgrade Its Drainage Master Plan

When the master plan for the drainage was last prepared in 1976, Delhi’s population was around 60 lakh.

However, the current estimated population living in and around Delhi is more than 2.5 crore, and the urbanised area is expected to be around 920 sq. km according to the its masterplan.

Over the years, the storm-water drains have become congested due to population growth and unauthorised construction activities.

According to earlier reports, in 2011, the Delhi government entered a contract with IIT-Delhi to develop a drainage master plan, which was submitted in 2018. However, the plan was implemented in 2021 but later abandoned due to its generic nature and lack of actionable points.

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.

In April 2023, bids were invited to hire companies that will oversee a master plan for the drainage network in the Barapullah and Trans-Yamuna basins.

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.

However realistically, a new drainage master plan is not expected to materialise and be implemented before the 2025 monsoon season.