NDTV Explainer: Why Delhi Was Flooded This Monsoon

For days, vast stretches of Delhi have been inundated due to the Yamuna river reaching its highest water level in 45 years, triggered by uncommonly heavy rainfall, some of which came from the neighboring state of Haryana.

The flooding has displaced residents, submerged historical sites and roadways, claiming at least three lives. Officials and relief workers have been working to open jammed floodgates and repair broken drain regulators to control the water levels.

Here are 5 reasons why the monsoon crippled Delhi:

Haryana floodgates open

The release of water from the Hathnikund barrage in Haryana is being blamed as one of the factors that contributed to the waterlogging in the national capital.

The Hathnikund barrage is situated on the border between Yamuna Nagar district in Haryana and Saharanpur district in Uttar Pradesh. The barrage is managed by the Haryana government.

The barrage was filled to capacity after receiving a large influx of water from Himachal Pradesh, which had recently experienced heavy rainfall. Typically, it releases 352 cusecs of water per hour. However, the amount of water released increases when there is heavy rainfall in the catchment areas.

The water level in the Yamuna river rose after the recent rains, causing the discharge from the barrage to spike. On July 9, at 4 pm, 111,060 cusecs of water was released from the barrage. This is considered a "flood situation", as the release of more than 1 lakh cusecs of water is considered a flood. The water release continued to rise, and on July 11, at around 11 am, 3,59,769 cusecs of water was released from the barrage.

This led to the floodwaters entering several parts of Delhi, submerging entire localities and triggering a blame game between the AAP government in Delhi and the BJP-led government in Haryana.

Unprecedented rainfall

Torrential rains lashed North India last week, causing widespread flooding, landslides, and other rain-related incidents. The weather office attributed the unprecedented rainfall to the confluence of a western disturbance and monsoonal winds.

The heavy rain, coupled with the Yamuna breaching its danger level by about 3 metres, led to several localities in the national capital being flooded.

Heavy rain pounded Delhi again yesterday as the city continued to battle the severe flooding. The incessant downpour has exacerbated the challenges faced by the authorities as it is taking more time to drain the floodwaters, officials said.

Blocked regulators

On Friday, Delhi Chief Minister Arvind Kejriwal claimed that the breaching of the Indraprastha water regulator was one of the major reasons why Delhi experienced flooding.

A regulator is a low-head dam or weir that controls the flow of floodwater back to the main channel from floodplains and diversion areas.

A regulator on drain number 12, which carries water from central Delhi to the Yamuna, broke down Thursday evening around 7 pm. This caused a backflow of water into the drain, which led to flooding in the ITO and surrounding areas.

Encroachments

Experts attributed another reason for the severe flooding to the encroachment of the Yamuna floodplains.

"We noticed that the water released from the Hathnikund Barrage took less time to reach Delhi compared to previous years. The main reason could be encroachment and siltation. Earlier, the water would have had more space to flow. Now, it passes through a constricted cross-section," a senior official at the Central Water Commission (CWC) said as quoted by PTI.

Too much, too soon

AAP leader Aatishi Singh have said recently that Delhi received 20% of the entire season's rain in 24 hours. Delhi, a city that historically does not receive rainfall of this magnitude on a regular basis, is not designed to handle floodwaters of this magnitude.

The first master plan for Delhi after Independence, which was drawn up in the 1960s, had a major flaw. This flaw has only gotten worse over time, and it has contributed to the current crisis.

"Delhi's first master plan after Independence was drawn up in 1962" and it made a "mistake" by treating the flood-prone Yamuna region as an "empty lot", AK Jain, the former Commissioner of the Delhi Development Authority (DDA), told NDTV.

"Delhi has been built and rebuilt many times over the last 1,000 years. There's a river on one side and a ridge on the other. Delhi has always been settled between them," he said.

Architect Edward Lutyens was aware that the Yamuna riverbanks were prone to flooding and malaria outbreaks when the British decided to make Delhi the capital. However, construction of the new capital proceeded anyway, as King George V had already laid the foundation stone.

The city's drainage system was designed in the 1970s for a population of 30-35 lakh. However, it is now overburdened by the current population of 2 crore.