‘Barrier lake’ flood risk adds new danger to desperate rescue efforts following China-Nepal disaster

Perilous rescue efforts along the China-Nepal border are being complicated by the risk of new flooding or landslides, with authorities in China and Nepal briefly pausing rescue operations Friday due to those fears. A barrier lake – holding enough water to fill an estimated 1,000 Olympic swimming pools – began overflowing on the China-Nepal border, where it formed after a powerful landslide and torrential flooding devastated the area on Wednesday. A barrier lake is a body of water created by debris damming up a river. Helicopter rescue operations in Nepal’s flood-hit Rasuwa district were stopped and locals were seen rushing up a hill after reports that the lake had begun to overflow, the Reuters news agency reported, citing a witness. Chinese state broadcaster CCTV reported late Friday morning the newly formed lake had begun overflowing, posing a risk of flash floods or landslides and prompting teams to pause efforts to reach the hard-hit Gyirong land port. Both teams resumed rescue operations later in the day after risk levels returned to what CCTV described as “manageable.” A Chinese team was dispatched to monitor the barrier lake, which sits some 10 kilometers upstream from Gyirong port, while others were analyzing the risks to rescue plans. A member of the monitoring team told CCTV early Friday that it stretched about 150 meters long and 40 or 50 meters high. “The rocks and soil along the area are currently loose. During the assessment operation, secondary collapses occurred several times above the barrier,” Chen Hanxiao, a member of the team dispatched by China Anneng Engineering Rescue Lhasa Base, told CCTV in the interview. Chen said safety personnel would monitor the area and “immediately withdraw” if they detected signals of significant displacement. Compounding risks Of key concern is how the barrier lake changes amid ongoing rain, which could add significant amounts of water volume – putting more pressure on the dam and creating further risk of breach. Recent floods have already weakened valley slopes, which could lead to further landslides, according to Manish Raj Gouli, a research scientist at the Stimson Center think tank in Washington, currently working with Nepal’s National Disaster Risk Reduction and Management Authority (NDRRMA) from Kathmandu. If there were a breach, flooding from the barrier lake would likely be less severe than on Wednesday, he told CNN, but would still create dangers for rescue teams on the ground. Blocked roads were limiting the monitoring of these risks on the Nepali side, he said, leaving teams dependent on updates from their Chinese counterparts who were able to access and monitor conditions at the lake directly. Gouli said such updates were being passed between authorities on both sides as well as between researchers. International researchers were also monitoring a second lake that formed after Wednesday’s disaster using satellite imagery, he said. That lake is located on the mountainside just below the fracture in a glacier that broke on Wednesday, causing the initial disaster. CNN has geolocated that area, which Chinese authorities are also monitoring. Broadcaster CCTV said that an avalanche of around 50,000 cubic meters of ice debris had entered the barrier lake Friday morning, prompting authorities to “step up monitoring.”