New Delhi | A cloudburst in Uttarakhand's Uttarkashi district has caused flash floods, wreaking havoc in high-altitude villages of Dharali. Here's an explainer on what a cloudburst is.
Counted among the most devastating natural disasters in the Indian Himalayas, a cloudburst causes an enormous amount of rainfall across a limited area within an extremely short span of time.
According to the India Meteorological Department, rain falling at a rate of over 100 millimetres an hour with strong winds and lightning across 20-30 square kilometres of area is termed a cloudburst.
However, in a 2023 paper, researchers from the Indian Institute of Technology, Jammu, and National Institute of Hydrology, Roorkee, define cloudburst as a "sudden downpour of rainfall in a range of 100-250 millimetres an hour in a short span covering a smaller spatial extent similar to one square kilometre". It is published in the International Handbook of Disaster Research.
The Indian Himalayas are considered vulnerable to unusual and extreme weather events, including cloudbursts, extreme precipitation, flash floods, and avalanches, the risk of all of which is said to increase as climate change intensifies.
Extreme rainfall events in the region, including districts in Uttarakhand and Himachal Pradesh, have been studied to commonly occur during the monsoon season.
This results in widespread damage to property and lives, and potential flash floods and landslides. Houses collapse, traffic is disrupted and human casualties occur on a large scale.
Occurrence of extreme weather events is frequent for locations at elevation 1000-2000 metres, "which are densely populated valley folds of the Himalayas," the 2023 paper says. Uttarkashi is located at about 1,160 metres above sea level.
Further, cloudburst events per unit area are "very high in Uttarakhand", compared to other regions in the Indian Himalayas, with recent events being more severe and impacting more communities, it says.
On July 26, heavy rains lashed Uttarakhand's Rudraprayag district, causing boulders to slide down a hillside and blocking the trekking route to Kedarnath. Over 1,600 Chardham pilgrims were evacuated to safety.
A sudden cloudburst on June 29 at Silai Band on the Barkot-Yamunotri Marg in Uttarakhand left an under-construction hotel site damaged and eight to nine workers missing, according to officials.
Researchers call for concrete policies, planning and management of cloudburst events by national and global organisations.
