Unchecked and ill-thought-out urban expansion is the main reason behind chronic urban flooding in Delhi, and the larger National Capital Region (NCR).

Last week, a spell of heavy rain brought parts of Delhi to a standstill. Streets across the city and in the larger NCR were inundated, leading to hours-long traffic snarls in some places. Water-logging also led to lengthy power cuts, property damage, and loss of life, with at least 11 people dying due to structural collapses and electrocution.

While the rainfall last week was unprecedented — the India Meteorological Department (IMD) recorded 228.1 mm rainfall in its Safdarjung station over a 24-hour period from June 27-28, an 88-year high — flooding and water-logging have now become a part and parcel of Delhi’s monsoons. Factors such as inadequate desilting of drains by civic authorities also play a part, but at the heart of it, Delhi is afflicted by a more fundamental problem.

A rapidly growing city

Delhi is undergoing one of the world’s fastest urban expansions. According to data from NASA’s Earth Observatory, the geographic size of Delhi almost doubled from 1991 to 2011.

Most of this expansion has occurred on the peripheries of New Delhi, with erstwhile rural areas becoming engulfed in the capital’s urban sprawl. Cities outside Delhi, but a part of the NCR — Bahadurgarh, Ghaziabad, Faridabad, Noida, and Gurugram — have also witnessed rapid urbanisation.

Festive offer

According to the United Nations’ The World’s Cities in 2018 data booklet, Delhi will overtake Tokyo as the world’s most populous city by 2030, with an estimated population of nearly 39 million, roughly two and a half times its population in 2000.

Topography and drainage

This urban expansion, however, has paid little heed to Delhi’s natural topography.

“Topography determines drainage patterns,” Manu Bhatnagar, principal director, Natural Heritage Division, INTACH, told The Indian Express. “If one looks at Delhi’s historic cities — from Tughlakabad, Mehrauli, and Shahjahanabad to Civil Lines, New Delhi, and the Cantonment area — all were carefully selected, and built on higher ground. In Delhi’s villages too, the center of the village would always be five to six meters higher than the village periphery,” he said.

How urban expansion makes Delhi susceptible to flooding

This allowed rainwater to drain out. But as the city has expanded, not enough thought has gone behind building with regards to the land’s drainage capacities.

Thus, with high-intensity rain there is significant run-off (unconfined flow of water, which occurs when there is more water on the land’s surface than it can absorb), and existing drainage systems have been inadequate, Bhatnagar explained.

Concrete everywhere

“The lay of the land slopes from the Ridge to the river… it is about a 100-metre drop,” KT Ravindran, architect and urban designer, told The Indian Express.

But due to urbanisation, water cannot simply flow down this gradient. “Today, much of the water gets channelised into concretised nallahs (drains), which have been turned into sewage dumps,” Ravindran said.

Construction in low-lying areas only makes things worse. For instance, many nallahs from across South Delhi, as far as Chanakyapuri and RK Puram, converge at Sarai Kale Khan, a low-lying area in South East Delhi, next to the Yamuna. This is why the bustling urban village sees intense flooding every year.

Construction in Delhi’s flood plains began as early as the 1900s, when the British decided to build a railway line along the river bed. Much later, the Ring Road came up, again on the Yamuna flood plain. Ravindran said that over the years, the floodplain has been used for all sorts of reasons, from building bridges to buildings.

Around 65 hectares of land on the flood plains near Kashmere Gate was reclaimed by the Delhi Metro for its maintenance shed. During the Commonwealth Games in 2010, a bus maintenance facility was built over roughly 25, again on the floodplains. The ITO-Pragati Maidan area, which has been seeing flooding for years, was once a low-lying wetland.

This concretisation leaves little room for rainwater to percolate into the soil, leading to flooding. As environmentalist CR Babu, who helmed the ecological restoration of the Yamuna Biodiversity Park (YBP), said: “When storm drains are converted into sewers and land has been concretised, where will the water go?”

No ‘water master plan’

Ravindran, who was Delhi Urban Arts Commission (DUAC) chairman from 2008-2011, said that urban planners need to come up with a “water masterplan”.

“Today, land is seen as real estate. There has been a consistent neglect of water as a planning resource… In fact, water should be the primary driving factor behind any masterplanning,” he said. He added that no comprehensive planning taking into account the city’s clean and waste water flows has been carried out in the last 70 years.

This is why, for example, the new Pragati Maidan Tunnel, inaugurated by the Prime Minister in 2022, has been flooded every monsoon.

Water bodies which can help manage flooding have also been systematically destroyed. According to official records, Delhi has some 1,000 water bodies. But on the ground there are not more than 400. These 600 ‘missing’ water bodies which could have managed flooding in the city have been filled up, and converted into valuable real estate,” Bhatnagar said.

Babu compared flooding in other parts of the city to the YBP — despite hours of intense rain, all the water successfully percolated into the park’s soft soil and rainwater harvesting pits. Much of the city, however, has not been planned so well, he said.

As Babu put it: “Unless we stop building in low-lying areas, de-concretise our lawns and pavements, and stop blocking the drains with solid waste, the floods won’t stop. Understanding gradients and working with the lay of the land is crucial”.

Ravindran suggested setting up proper filtration pits to carry the water to aquifers in low-lying areas. “We can’t afford to pump out all of the water every time. We have to rely on gravitational flow, but ensure the dirty water does not go into the aquifers,” he said.