Mountains Face Growing GLOF Threat

At around 6:00 on the morning of June 23, 1980, Chunglamo Sherpa was grazing yaks in a large open pasture above Olangchung Gola in northern Taplejung when she heard a loud crash echoing through the mountains.

She did not know what was happening. Then the flood came. Water, rocks and debris rushed down the valley after Nangama (Nagi) glacial lake burst high above the settlement. Chunglamo and her husband, Chosang, ran towards higher ground. They survived because they were near the edge of the pasture. Others were not so fortunate.

“If we had been in the middle of the taar (field), we all would have been swept away,” Chunglamo recalled. “We were saved only because we were near the edge.”

Nearly 46 years later, the memory of that flood remains alive in Olangchung Gola and in the memory of Sherpa. The settlement lies at around 3,200 metres above sea level in the upper Tamor valley, surrounded by glaciers, glacial lakes, steep slopes and narrow valleys.

The flood swept away ten people, including two neighbouring children. Sherpa and her husband, Chosang Sherpa, managed to escape just in time. The flood destroyed their house and livestock shed and swept away six yaks belonging to her brother-in-law.

The Nangama Glacial Lake Outburst Floods (GLOF) was triggered when an avalanche entered the lake and generated a large impulse wave, according to a study titled “Reconstructing the history of GLOF in the Kanchenjunga Conservation Area (KCA), East Nepal: An Interdisciplinary Approach”.

The study was conducted by researchers including Dr. Alton C. Byers, a US-based mountain geographer and glaciologist associated with the Institute of Arctic and Alpine Research (INSTAAR) at the University of Colorado Boulder, and KU Associate Professor Dr. Mohan Bahadur Chand.

The flood originated from Nangama Glacial Lake in the Kanchenjunga region of eastern Nepal, about 8 km south of the Tibetan border. Debris from the flood dammed the Pabuk Khola about 2 km downstream, forming what is now known as Chheche Pokhari Lake, according to a 2020 study by the team.

The Nangama event was identified as one of the largest GLOFs recorded in the region, while ongoing landslide activity along the lake’s right lateral moraine has raised concerns over the possibility of another GLOF.

Dr. Chand said scientific studies and accounts from local historians indicate that at least six GLOF events occurred in the KCA up to 1980.

Another witness to the 1963 GLOF, Chungdak Sherpa, now 76, recalled that he was seven years old when the flood struck Olangchung Gola at around 6 to 7 p.m. He and his sister were in their fields when a debris-laden flood suddenly swept through the area, destroying houses and farmland.

They ran towards the Olangchung Gola monastery for safety along with other villagers. The monastery, located within the settlement, became one of the places where villagers sought refuge as the flood moved through the lower parts of the village. By the following morning, several houses and large areas of farmland had been swept away.

Chungdak said the disaster originated after a lake near the foot of the Khanglung Himal burst. Water initially flowed down as a small stream, but as it carried away trees, rocks and other debris, the flow became increasingly destructive and eventually swept through the settlement.

No one in the village was killed, as residents managed to flee in time. However, the flood destroyed much of the village and farmland. He recalled that the area gradually became more unstable, with houses collapsing one after another as the river deepened and eroded the land.

He also recalled that the lower part of the village, which once had a large market, was almost completely swept away. Only a small section of the market remains today.

Olangchung Gola lies at around 3,200 metres above sea level in the upper Tamor valley of northern Taplejung, close to the Nepal-China border. The remote settlement, historically a trading post on the route to Tipta La Pass, is part of the 2,035-square-kilometre Kanchenjunga Conservation Area, where the landscape rises from about 1,200 metres to the 8,586-metre summit of Mt. Kanchenjunga and includes steep valleys, glaciers, high-altitude lakes and deep mountain gorges.

This rugged terrain, combined with narrow valleys and numerous glaciers and glacial lakes, leaves settlements and infrastructure downstream exposed to sudden flows of water, ice and debris.