Climate change triggering cloudbursts in Himachal Pradesh

This monsoon, Himachal Pradesh has seen an unusual number of rain-triggered flash floods and incidents of cloudbursts, prompting environmental experts to raise climate change concerns.

Since the onset of monsoon on June 29, the hill state has seen 12 cloudbursts, 64 flash floods and landslides at 71 places. As a result, 250 people have died in rain-related incidents and the state has suffered losses estimated at ₹1,337 crore.

The State Disaster Management Authority has written to the Centre for Climate Change to analyse and prepare a report, ascertaining the reasons for the phenomenon.

Studies carried out by experts have found that the higher regions of the Himalayas and the Tibetan plateau have experienced substantial warming during the 20th century and the temperatures are generally higher than the low-lying areas by about 0.2 degrees Celsius per decade from 1951-2014. Future projections indicate the warming of the region in the range of 2.6-4.6 °C by the end of this century.

“In the present scenario of climatic variations, incidences of extreme weather events such as drought, heavy rainfall, floods, landslides and avalanches are some of the common effects of climate change,” says Dr SS Randhawa, who has been associated with the Himachal Pradesh Council for Science, Technology and Environment since 1993 and is the principal scientific officer at present.

“This year, the abrupt rise in the temperatures in March and April led to the early melting of the snow cover as a result of which the discharge dependability of the major river systems in the Himalayan region, particular Himachal Pradesh, had adverse effects,” he says.

The rainfall has been more in certain districts, particularly Kangra, Chamba, Mandi, Shimla and Kullu. What is more concerning is that the cold deserts of Lahaul and Spiti and Kinnaur districts witnessed flash floods.

“The recent spells of extremely heavy rainfall in parts of Kangra, Chamba and Mandi can be attributed to strong Arabian Sea monsoon currents. The location of the monsoon trough near the foothills and interaction of mid-latitude westerlies led to high-intensity rainfall in the area,” says Shimla-based Indian Meteorological Department director Surender Paul.

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Fact check on cloudbursts

Most of the flash flooding and cloudbursts occurred during the night and early in the morning in the state. Cloudburst is a local phenomenon. It can occur during heavy rainfall with 4mm to 6mm droplets. A cloudburst occurs when moisture-rich air travels up a mountainous region, forming a vertical column of clouds called Cumulonimbus clouds. These clouds usually cause rain, thunder and lightning. This upward movement of clouds is also known as orographic lift. Due to these unstable clouds, heavy rainfall may occur over a small area.