Climate change prompting more frequent, unpredictable floods in mountains of HKH

By A Staff Reporter

Kathmandu, Mar. 2: Climate change is driving more frequent and unpredictable floods in the mountains of the Hindu Kush Himalaya (HKH), scientists warned. 

Analysing 73 years of flood data, researchers found that rising temperatures are increasing flood risks and adding complexity to water management in High Mountain Asia.

A new analysis of 1,015 floods in High Mountain Asia, just published in Science Bulletin, confirmed a significant rise in the frequency of floods since 2000 and confirms that temperature rise is driving the increase, said a press statement issued by the International Centre for Integrated Mountain Development (ICIMOD) on Friday. 

The study, Flood Complexity and Rising Exposure Risk in High Mountain Asia under climate change authored by Peking University’s Dongfeng Yi, ICIMOD Cryosphere Specialist Sonam Wangchuk, Peking University Yuanyuan Bai, University of Colorado’s Albert J. Kettner, is grounded in a new inventory of the types, patterns and causes of floods in the region stretching back to 1950.

Flood frequency has risen, the study confirmed, but a key additional finding is a rise in the unpredictability of the timing of floods, while most events continue to occur during monsoon, there is a marked rise in the number of floods happening outside these times. 

The study also confirmed that planetary heating from the burning of oil, coal and gas is driving the rise in all four of the main types of floods seen in the region.

According to the press release, the two most common are driven by rain and snowmelt. Less common, but more sudden and highly destructive are those that are caused by glacial lake outbursts (GLOFs) and landslide-dammed lake outburst floods (LLOFs).

While population rise and expansion of infrastructure are increasing risk exposure, temperature rise is the key factor in the rise in the number of all four categories of floods.

“The rules of floods are changing and the window for adaptation is closing,” warned Wangchuk, one of the report’s authors. “A single monsoon cloudburst or glacial collapse can trigger cascading disasters, overwhelming unprepared regions,” he said.

“We should prioritise real-time monitoring of floods in vulnerable valleys, restrict infrastructure projects in high-risk zones and strengthen data-sharing agreements between High Mountain Asia nations to address transboundary threats,” according to him.

“[While] pluvial and snowmelt floods... result from extreme rainfall,” report author Dongfeng Li, principal investigator of the Cryosphere and River Lab at Peking University, said, “snowmelt floods are driven by rising temperatures and increased soil moisture. In contrast, GLOFs and LLOFs [are] shaped by complex interactions between climate, glaciers, and topography." 

Human activities are hugely aggravating the risks from floods, especially urbanisation and land use changes, such as human settlements in flood plains, deforestation, and dams, which can all increase vulnerability and reduce natural buffers.

The study is published in February’s edition of Science Bulletin, a peer-reviewed international journal, which is sponsored by the Chinese Academy of Sciences and the National Natural Science Foundation of China, the release said.