What are the reasons for Delhi flood?
Heavy rainfall and Climate change:
Heavy rainfall associated with the monsoon.
According to the India Meteorological Department (IMD), north-west India experienced 59% excess rainfall than what is normal in the first fortnight of July.
This occurred due to active monsoon conditions and a passing ‘Western Disturbance’ or an extratropical storm originating in Central Asia.
The excess rainfall resulted in flooding, water-logging, and loss of property, leaving some areas paralysed for days.
Yamuna’s floodwaters kept rising.
The spate of the Yamuna was due to heavy rainfall in Himachal Pradesh and other upper reaches, which are upstream of Delhi.
The ongoing spell of extremely heavy rains is due to the alignment of three weather systems.
One, the Western Disturbance over the Western Himalayas.
Two, the cyclonic circulation over the north-western plains.
And three, the Axis of Monsoon trough running across Indo-Gangetic plains.
This a giant belt of low pressure located in the east-west direction from north-west Rajasthan till the Bay of Bengal.
Its movement influences the quantity of rainfall in monsoon.
This alignment is not happening for the first time; it is the usual pattern during the monsoon.
However, global warming-led changes in monsoon patterns have made a difference.
There has been a constant rise in both land and sea temperatures, which has increased the capacity of the air to hold moisture for a longer time.
Thus, the role of climate change in the increasing extreme weather events in India has been strengthening with each passing year.
Encroachments on the floodplains:
The journey of the Yamuna through Delhi is uneven.
The width of the river can range from 800 metres to 3 km at various stretches.
Experts have been saying for decades that the floodplains should be free of encroachments and large settlements, to aid the natural course of the river.
Maximum distance between the two embankments of the river was less than 2 km.
As a result, the floodwater-carrying capacity of the river had been greatly compromised.
More illegal encroachments on the floodplains have left less space for the river to flow and for the water to percolate.
Since 1987, nearly 14 bridges have been constructed between the city’s Wazirabad and Okhla barrages. These contribute to the city’s flooding woes.
Apart from illegal encroachments, many official developmental works such as the Akshardham Temple, the Commonwealth Games Village, the Yamuna Bank Metro Station, and the Delhi Secretariat are built on the Yamuna floodplains.
Hathnikund barrage:
During the floods, water is released from Hathnikund barrage in Haryana.
The water level of the Yamuna in Delhi depends heavily on the amount of water that is released from barrage.
After the Yamuna enters Delhi at Palla, it flows through Wazirabad to reach ITO, located at the heart of the city, before exiting from the Okhla barrage.
The ITO barrage, though located in Delhi, is owned by the Haryana government.
The Delhi government has alleged that five of the 32 gates of the barrage were “stuck,” which caused the flooding in parts of Delhi.
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