Did over 100 mm of rain in an hour lead to flooding in Delhi? Why is the capital struggling with floods? – Firstpost

The rain gods unleashed their wrath on India’s capital on Wednesday evening (July 31), bringing Delhi and surrounding areas of the National Capital Region to their knees as torrential downpours flooded streets, caused flight delays and even death and destruction.

In view of the situation, the Delhi government has announced that all schools will remain closed from today till August 1. Further, the Indian meteorologist, India Meteorological Department (IMD), has issued a red alert, urging citizens to stay indoors and avoid travelling.

But what caused this fury of rain? And how much damage did it cause? Here’s what we know so far.

Heavy rain?

Delhi turned into a watery mess on Wednesday evening after heavy rainfall lashed the city in a short span of time. The capital recorded more than 100 mm of rainfall in an hour, leading to flooding in several areas of the national capital and prompting the meteorological office to issue a red warning.

According to IMD’s network of Automatic Weather Stations (AWS), the Pragati Maidan observatory in central Delhi recorded 112.5 mm of rainfall in one hour.

Incidentally, the IMD describes extreme rainfall in a short period of time, specifically 100 mm of rainfall in an hour, as a “cloudburst.” However, officials have not called this rainfall a cloudburst.

But what caused this sudden heavy rainfall? The IMD at around 7 pm on Wednesday said in X, “Clouds have converged over Delhi from all four sectors. Widespread light/moderate rainfall with isolated heavy to very heavy spells (3-5 cm/hr) likely over Delhi during the next two hours.”

Later, the IMD also forecasted that rainy conditions would continue till August 5.

How heavy was the rainfall?

Heavy rains caused chaos in the nation’s capital on Wednesday, flooding large parts of the city. This led to endless traffic jams and people stranded on river-like roads.

In Ghazipur, east Delhi, a woman and her three-year-old son fell into a flooded drain and drowned. The police in their report identified the victims as Tanuja and Priyansh, adding that they had gone out to buy household items when they slipped and fell into the drain. The incident took place near Khoda Colony, where a roadside drain was being constructed.

According to reports, three other people from Gurugram also died in the flood, taking the death toll to five.

Heavy rains also led to the collapse of a house in north Delhi’s Sabji Mandi area near Robin Cinema, injuring one person. Authorities also reported a wall collapse in southwest Delhi’s Vasant Kunj area, injuring a woman.

In Pragati Maidan area, officials recorded 112.5 mm of rain in an hour, leading to waterlogging and mess. The IMD also recorded 79.2 mm of rainfall between 5.30 pm and 8.30 pm in Safdarjung. During the same time, Mayur Vihar recorded 119 mm of rainfall, while Delhi University recorded 77.5 mm of rainfall, Pusa recorded 66.5 mm and Palam recorded 43.7 mm of rainfall.

Flooded streets in Lutyens’ Delhi caused major traffic jams, with people complaining on social media about the roads and the watery mess. Visuals from several places in Delhi showed vehicles wading through flooded roads as traffic police officers tried to control the movement of vehicles.

One image shared online also showed rainwater pouring into the Press Club of India, where people were sitting in knee-deep water. In other parts of the capital, visuals showed water pouring into showrooms and restaurants. Parts of Delhi even lost power during the rain, with many residents forced to sit in the dark for hours.

Incidentally, in Old Rajinder Nagar, where students protested against the death of three UPSC aspirants in the basement of the coaching institute, the water was knee-deep.

The weather also affected air travel. At least 10 flights scheduled to land at Delhi airport were diverted — eight to Jaipur and two to Lucknow — due to the adverse weather. Airlines also warned of further flight disruptions.

The downpour and subsequent water mess prompted Delhi Governor VK Saxena to ask officials to remain vigilant. Meanwhile, Delhi Education Minister Atishi announced that all schools in the city would remain closed on Thursday. “In view of very heavy rainfall tonight and forecast of heavy rainfall tomorrow, all schools, both government and private, will remain closed on August 1,” she wrote on X.

Why is Delhi struggling with floods?

Wednesday’s rain caught Delhi by surprise, as it has been experiencing drought and heat. However, Wednesday’s rain chaos is nothing new in the capital. Delhi and the surrounding NCR region battle floods almost every year.

But what’s causing this mess? Experts say Wednesday’s rain was torrential and unexpected. Too much, too soon, they say. Records show that more than 100 mm of rain fell in an hour in some parts of the capital.

But it is not just the unprecedented rainfall that is causing these floods. Uncontrolled and ill-considered urban expansion is also a reason for Delhi’s struggles. According to data from NASA’s Earth Observatory, Delhi’s geographical area has almost doubled from 1991 to 2011.

However, this expansion does not take into account the topography of the area. Manu Bhatnagar, Chief Director, Natural Heritage Division, INTACH, explained Indian Express“Topography determines drainage patterns. If you look at the historic cities of Delhi—from Tughlakabad, Mehrauli and Shahjahanabad to Civil Lines, New Delhi and the Cantonment area—all were carefully selected and built on higher ground. In the villages of Delhi too, the village centre has always been five to six metres higher than the village outskirts.”

This allowed for rainwater to drain away. However, as the city grew, not enough attention was paid to the building’s drainage capabilities.

Constant construction doesn’t help either. Concreting leaves little room for rainwater to soak into the ground, leading to flooding.

The constant encroachment on the Yamuna floodplains is also a cause of floods in Delhi. Hundreds of thousands of people live on the Yamuna floodplains in the city and many of them have converted the area into farmlands to earn a living. According to a report by the Centre for Science and Environment, the Yamuna floodplain had over 600 wetlands and water bodies, but “more than 60 per cent of them are devoid of water, making the city prone to floods”. The report further stated that “river-fed water bodies in the Yamuna floodplain are disconnected from the river due to embankments”.

With information from the agency