Come and see the flood in the streets

P Anima | Updated on February 21, 2020

Under water: Mumbai experienced such heavy downpours in 2019 that it was flooded five times - Yogesh Mhatre

High-intensity rainfall and floods are becoming a norm in Indian state capitals

It never rains but it pours, goes the old saying. Mumbai knows this well. The Maharashtra capital experienced such heavy downpours in 2019 that it was flooded five times. And it’s not just Mumbai; state capitals across the country have seen a rise not just in the intensity of rainfall, but in instances of flooding.

Bhopal, Jaipur, Lucknow, Ranchi, Raipur. Pick any Indian state capital — even one traditionally not linked with very heavy rainfall — and in all likelihood it would have been flooded sometime between June 2018 and May 2019.

The situation is getting worse, warns Kapil Gupta, professor, water resources engineering at the Indian Institute of Technology, Bombay, and the author of a paper published earlier this week in the UK-based The Royal Society’s Philosophical Transactions, the world’s first and longest-running scientific journal.

In Challenges in developing urban flooding resilience in India, Gupta maps the amount of rainfall received between June 2018 and May 2019 by 33 cities — state capitals and a few Union Territories — and finds that all the capitals received more than 50mm rainfall over a single day, flooding parts of the cities. Seventeen cities, including Mumbai, Kolkata, Bhubaneswar and Dehradun, were pelted with more than 100mm rainfall recorded over just one day.

Gupta and his team are now compiling rainfall data for 2019-20 and there are already enough surprises. “The amount of rainfall has doubled in a few cities,” Gupta adds.

In 2018-19, Patna received 50mm rainfall a day on a single occasion. But from June to December, 2019, it received the same intensity rainfall on seven instances — leaving parts of the city under water. Bhopal, which did not have instances of 100mm rainfall in one day in 2018-19, received high intensity rain on four occasions in the second half of 2019, even recording a high of 170mm rainfall on July 29 last year.

“We hardly ever heard of flooding in cities such as Dehradun; but ever since the Uttarakhand (flooding) disaster of 2013, the city has been flooded almost every year,” Gupta tells BLink. The city on the foothills of the Himalayas received more than 100mm rainfall a day thrice in 2018-19.

The data in the report, compiled from the Indian Meteorological Department’s daily weather reports, hold a mirror to the precarious state of capital cities.

“The intensity of rainfall over the capital cities has definitely increased. More and more cities are receiving over 100mm of rain a day,” Gupta says. Mumbai, for instance, received more than 100mm of rainfall in a day on nine occasions in 2018-19. It even recorded 230mm of rain over a day.

Climatic changes aside, the professor, in his paper, notes the part played by indiscriminate urbanisation and systematic degradation of low-lying areas in heightening the flood vulnerability of cities. “When roads were widened in Delhi in preparation for the Commonwealth Games, many existing drains were either narrowed or blocked. As a result, if the Capital receives about 20mm of rain, some parts of it come under water. Even 7-10mm rain is enough to bring traffic to a standstill in parts of the city,” Gupta says.

Every state capital in its bid to grow has trampled upon natural and man-made drainage mechanisms. “Works on bridges and metro rail often interfere with the existing drainage systems,” Gupta says, pointing out the degradation of Chennai’s Buckingham Canal owing to metro rail construction. In Bengaluru lakes have been lost as buildings came up on them. “In Gurugram, one cannot see any open storm water drains. Rapid urbanisation has a double impact; it has reduced the groundwater recharge and increased surface run-off resulting in flooding of our cities,” he adds.

In addition to the structural degradation, capital cities also witness large-scale migrations from rural areas which put intense pressure on its limited land and water resources. “The rate of population growth in the cities has outpaced the development of the sewer systems,” the paper states.

Rapid urbanisation has also meant over-burdened municipal corporations. In the paper, Gupta refers to the Hyderabad Municipal Corporation that once covered an area of 172 sq km. It was upgraded to the Greater Hyderabad Municipal Corporation in 2007, and spread over 778 sq km.

“The adjoining areas which had a water infrastructure based on rural needs suddenly found themselves transformed into an urban landscape with multi-storeyed buildings and severely lacking urban water supply, sewerage and drainage infrastructure,” the author notes in the paper.

The vulnerable urban scene is further compromised by heavy rainfall in the capital cities. Panaji, he points out, has not seen very rapid urbanisation and the terrain is hilly which allows water to flow into the sea. “The city has not been flooded, but has witnessed very high intensity rainfall from June to December, 2019,” he says.

The paper recommends better planned storm water drainage systems in the cities to mitigate flooding. There are other measures too, such as automatic weather stations for rainfall monitoring and dissemination of real-time flood alerts. Structural interventions such as the creation of detention ponds (basins in excavated land near rivers and lakes) are found to be effective in reducing flooding.

“It is high time planners woke up and took note of these developments. Most of these capitals are part of the Smart City Mission. All of which goes on to show that we are not that smart after all; it's time we stepped in to protect our cities,” Gupta says.

Published on February 21, 2020

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