Studies show frequency of cloudbursts increasing

Hindustan Times

2 days ago

The flash flooding and landslide triggered by torrential rain in Jammu and Kashmir has brought the spotlight on extreme weather events battering India's Himalayas this monsoon season, a trend that tracks with rising extreme weather events as global temperatures have risen. The incident in Jammu and Kashmir comes on the back of another deadly flood on August 5, when suspected glacier collapse triggered flash floods in Dharali region of Uttarakhand(PTI)
The incident in Jammu and Kashmir comes on the back of another deadly flood on August 5, when suspected glacier collapse triggered flash floods in Dharali region of Uttarakhand. Extreme monsoon rainfall and flash floods also struck Kullu, Shimla, Lahaul and Spiti this week, continuing a pattern of escalating disasters across Uttarakhand, Himachal Pradesh and Jammu and Kashmir.
Multiple peer-reviewed studies published since 2017 have documented the increasing frequency of cloudbursts and flash floods across the Western Himalayas. Experts attribute this to rising temperatures that increase the atmosphere's water-holding capacity, leading to more intense rainfall events, compounded by unplanned construction in vulnerable areas.
The physics behind the increasing intensity are straightforward, according to Anil Kulkarni, distinguished visiting scientist at the Divecha Centre for Climate Change at the Indian Institute of Science.
'Higher temperature increases water holding capacity of the air,' Kulkarni explained. 'Mountainous regions due to higher slope are associated with upward movement of air mass. As atmospheric moisture is moved upward it increases size of water droplets, in the meantime, additional moisture is added at lower altitude. This significantly increases moisture in the air column. This leads to cloudburst.'
Research data supports this mechanism. A study published in July in the Journal of Geological Society of India titled 'Uttarakhand: A Hotspot for Extreme Events?' documented a marked increase in extreme events over Uttarakhand after 2010, particularly during monsoon season.
The research, led by Yashpal Sundriyal of Hemvati Nandan Bahuguna Garhwal University, analysed four decades of observational data from 1982 to 2020, including rainfall, surface radiative temperature, surface runoff and teleconnection indices. The study examined relationships between climate variability and global teleconnections including the North Atlantic Oscillation and El Niño-Southern Oscillation. Notably, the period 1998-2009 showed increased annual temperatures and decreased precipitation and surface runoff.
A 2025 study published in Springer Nature titled 'A review of cloudbursts events in the Himalaya region, and 2D hydrodynamic simulation using MIKE models' found cloudbursts increasing in frequency across Uttarakhand, Himachal Pradesh, Jammu and Kashmir and Ladakh based on analysis from 1970 to 2024.
Uttarakhand emerged as the most affected area, with Himachal Pradesh experiencing frequent events and Jammu and Kashmir showing rising trends. 'The region is characterised by frequent extreme rainfall events during the Indian Summer Monsoon and winter western disturbances,' the July study concluded.
The escalating pattern builds on documented disasters, like the August 18, 2019 cloudburst in Uttarkashi's Arakot region that killed 19 people while affecting 38 villages across 70 square kilometres and stranding more than 400 people. Heavy rain caused a massive flash flood in Arakot Nala and induced a major landslide downstream, devastating the villages of Tikochi and Makudi.
Climate change compounds the risk by exposing retreating glaciers to collapse. The Indian Institute of Science suspects a 'hanging glacier' feeding the Kheer Ganga channel contributed to the August 5 Dharali floods, while the National Disaster Management Authority's preliminary analysis indicated glacier collapse may have triggered the disaster, HT reported last week.
The Divecha Centre has identified 219 hanging glaciers in the Alaknanda and Bhagirathi basins as part of ongoing geo-spatial mapping in Uttarakhand. Most glaciers are receding due to global warming, leaving them exposed to various disasters and collapse.
Poor land use planning amplifies the destruction when extreme weather strikes, experts warn.
'These kinds of rainfall events are rare and take place once in 20 or 50 years. However nowadays such events are becoming frequent due to climate change,' said Manish Shrestha, hydrologist at the International Centre for Integrated Mountain Development. 'Such mudslides normally happen when there is very heavy rain upstream.'
Referring to the Dharali disaster, Shrestha noted dense settlements near riverbanks that fall 'in the right of way of the river.' 'We should have a safe zone for buildings, hotels, and habitations. Zonation is important in such regions,' he said.
The Western Himalayas' unique topography creates conditions ripe for extreme weather events. A 2024 paper published in the National Library of Medicine, led by the Centre for Remote Sensing and Geoinformatics at Sathyabama Institute of Science and Technology along with the India Meteorological Department, investigated the Nainital region of Uttarakhand and found correlations between pre-flood parameters including total aerosol optical depth, cloud cover thickness and water vapour.
'The Himalayan region, characterised by its substantial topographical scale and elevation, exhibits vulnerability to flash floods and landslides induced by natural and anthropogenic influences,' the study noted.
Scientists have repeatedly called for comprehensive disaster preparedness measures to address the growing threat.
The 2022 Geological Society of India study, titled: 'An Investigation of Cloudburst-triggered Landslides and Flash Floods in Arakot Region of Uttarkashi District, Uttarakhand' recommended 'pragmatic check dam policy and logical shifting of people' to safe areas before monsoon season in hazard-prone regions.
Researchers from the Wadia Institute of Himalayan Geology noted such measures including early warning systems, Doppler radar installation and lightning sensors 'would be helpful for policymakers, planners, practitioners, and technologists' to aid sustainable development within the region.
The pattern contrasts with neighbouring Nepal, where a 2024 study of 1971-2015 data found extreme daily rainfall declined overall, with western mountains getting wetter and eastern regions becoming drier after 2003.