China halts rescues as glacier-dammed lake starts to overflow
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Rescue workers repair a damaged road leading to Gyirong Port following a mudslide on Aug 27.
PHOTO: REUTERS
- A glacier collapse on the China-Nepal border formed a debris-dammed lake that has started to overflow, forcing Chinese rescue teams to halt operations due to high flood risks.
- The lake holds over 2.5 million cubic metres of water, with heavy rainfall forecast to add 3 million cubic metres, raising the risk of a catastrophic breach around Sept 1.
- Nearly 1,000 people remain missing from the disaster, including 540 foreigners, while engineers work on drainage plans amid challenging terrain and unstable conditions.
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BEIJING – A lake formed by debris from a glacier collapse that triggered catastrophic flooding on the China-Nepal border has begun to overflow, the Chinese authorities said on Aug 28, forcing rescue operations to be halted.
Nepal and China both warned on Aug 27 of fresh risks of flooding in the Himalayas, with a debris dam creating a lake upstream that has been threatening to collapse.
China has been racing to reduce the risk of more flooding at the disaster-stricken border crossing linking its Tibet region to Nepal, after hundreds were killed in a flash flood on Aug 26.
Risks of the lake bursting and potential secondary disasters such as mountain collapses and avalanches have prompted all Chinese rescue personnel and vehicles to withdraw to stand by in a safe area, state broadcaster CCTV said.
The lake’s reservoir has topped 2.5 million cubic metres of water, up from the estimated 1.5 million to 2 million cubic metres a Chinese eight-member engineering team dispatched to monitor the site recorded a day ago.
The Chinese authorities have mobilised an eight-member engineering team to conduct aerial surveys and 3D modelling of the barrier lake, according to CCTV.
One of the engineers, Chen Hanxiao, said challenges included difficult access to the site.
“After the glacier collapse created the lake, many isolated cliffs and steep cliffs appeared along it,” Chen told CCTV on the evening of Aug 27.
Chen said the general approach to reducing the lake’s threat is to excavate a drainage channel at a lower point of the dam but the width and depth of that channel needed calculations based on how fast the water will flow and how quickly the lake will fill.
Data from their survey found that the lake was about 150m long and 40m to 50m deep.
The Gyirong border port area has seen light to moderate rainfall which has loosened and destabilised soil and rock surrounding the precarious zone upstream. The rain is forecast to continue over the coming week.
China on Aug 27 warned that 3 million cubic meters of water – the equivalent of about 1,200 Olympic swimming pools – are expected to flow into the still-dammed lake over the next three days, creating a high risk of a breach, with peak flow expected around Sept 1.
The formation of a barrier lake was captured in aerial footage by a Chinese rescue team shown by state broadcaster CGTN. It showed masses of brown water accumulating in a basin with no visible outlet, that had already submerged bushes and trees and appeared to push against a barrier of debris and stones.
Nearly 1,000 remain missing on both sides of the border, including as many as 540 foreigners from 31 countries, according to officials. REUTERS
