Ice-rock avalanche may have triggered surge in border river, say experts, Pg1

Key Highlights:

• Scientists are investigating whether an ice-rock avalanche from a high-altitude area triggered flash floods and a mudslide on the Nepal-Tibet border.
• The event occurred in the Lhende Khola, a tributary of the Bhote Koshi river, causing a sudden surge of water, sediment, and boulders downstream.
• The International Centre for Integrated Mountain Development (ICIMOD), a Nepal-based intergovernmental institution, is leading the assessment.
• Water levels in the Trishuli river reportedly rose by nine meters at Galechhi and seven meters at Malekhu within 30 minutes in Dhading district.
• Authorities have warned of a potential second flood due to a blockage still lodged upstream on the Nepal-China border.

Nepal Flooding Reasons.jpg

Detailed Insights:

• The suspected ice-rock avalanche involved the sudden collapse of a large mass of ice and rock debris into the Lhende Khola.
• Preliminary analysis of seismic records identified unusual signals during the disaster period, though a direct link to the flood is unconfirmed.
• The affected area was previously devastated by floods in Rasuwa last year, highlighting recurring vulnerability.
• ICIMOD experts are assessing if debris temporarily blocked the river, forming a landslide dam, which could create a secondary hazard if it breaches.
• The Hindu Kush Himalaya (HKH) region, where the incident occurred, is a critical mountain system spanning eight countries and is often called the "Third Pole" due to its vast ice and snow reserves.
• The Bhote Koshi river originates in Tibet and flows into Nepal, forming part of the Koshi River system.
• The Trishuli river is a major tributary of the Narayani River basin in central Nepal, formed by the merger of the Kyirong Tsangpo and the Lende Khola near the Nepal-Tibet border.

Key Concepts Involved:

• Ice-rock avalanche: A rapid downhill movement of a large mass of ice and rock debris, often from glaciers or ice-covered mountains.
• Landslide dam: A natural dam formed when a landslide blocks a river channel, impounding water upstream and posing a risk of catastrophic flooding if it fails.
• Hindu Kush Himalaya (HKH) region: An extensive mountain range spanning eight countries (Afghanistan, Bangladesh, Bhutan, China, India, Myanmar, Nepal, Pakistan), known as the "Third Pole" and a source of major Asian river systems.