Kathmandu: 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 that temperature rise is driving the increase.
The study, Flood complexity and rising exposure risk in High Mountain Asia under climate change authored by Peking University’s Dongfeng Yi, ICIMOD’s Cryosphere Specialist Sonam Wangchuk, Peking University’s 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 confirms but a key finding is that the unpredictability in the timing of floods is also rising, while most events continue to occur during monsoon, there is a marked rise in the number of floods happening outside these times.
The study confirms 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.
The two most common are driven by rain and snowmelt. Less common, but more sudden and highly destructive are those that caused by glacial lake outbursts (GLOFs) and landslide-dammed lake outburst floods (LLOFs). While population rise, and expansion of infrastructure is increasing exposure to risk, 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 Sonam Wangchuk, one of the report’s authors. “A single monsoon cloudburst or glacial collapse can trigger cascading disasters, overwhelming unprepared regions.”
“We should prioritize 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,” he added.
Authors emphasize that while climate change is aggravating the risks of all types of floods, there are complex dynamics at play in each type. “[While] pluvial and snowmelt floods… result from extreme rainfall,” report author Dongfeng Li, principal investigator of the Cryosphere and River Lab at Peking University, states. “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 urbanization and land use changes, such as human settlements in flood plains, deforestation, and dams, can all increase vulnerability and reduce natural buffers.
In the context of rising risks, the study’s authors urge greater emphasis on community-based flood mitigation efforts including community awareness programs, locally-led construction of protective infrastructure, and local emergency planning.
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.
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