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News: A significant barrier lake formed on the Tibetan side after the August 26 glacier collapse, creating a fresh flooding threat for Nepal.
About Barrier Lake
- A barrier lake is a temporary water body formed when landslide debris completely blocks a river or stream channel.
- Formation:
- Triggering Event: A glacier collapse, landslide, rockfall or debris flow can dislodge rock, soil, mud and ice from steep mountain slopes.
- Natural Dam Formation: The displaced material blocks a narrow river channel, causing water to accumulate upstream and form a temporary reservoir.
- Key Features:
- Temporary Nature: Barrier lakes are temporary water bodies formed when natural debris blocks a river channel.
- Unstable Barrier: The natural dam consists of loose soil, broken rock, mud, ice and other debris, making its stability uncertain.
- Water Accumulation: Water accumulates behind the natural barrier, increasing pressure on it and potentially weakening it over time.
- Landslide Lake Outburst Flood (LLOF): When the natural barrier suddenly fails, the stored water is released rapidly, causing a potentially devastating flood downstream.
- Variable Lifespan: A barrier dam may fail within days or even decades after its formation.
Examples of Barrier Lakes
- 2026: A barrier lake formed near the Chhochen Khola–Purepu Tsangpo rivers along the Nepal-Tibet border.
- 2014: A landslide lake formed across the Sunkoshi River in Nepal after a huge landslide.
- 2008: Landslide dams formed along rivers near the Qinghai-Tibet Plateau after the Wenchuan earthquake.
- 2000: The Yigong landslide created a 60-metre-high dam on the Yigong Tsangpo River.
- 1835–1966: A rock-and-debris dam formed over the Tagermarch River in Kyrgyzstan and failed after 131 years.
