Risk assessment of debris flows along the China-Nepal transportation corridor

This study assesses the distribution, formation conditions and risk levels of debris flows along the China-Nepal Transportation Corridor, a major transport route connecting Lhasa with Zhangmu Port and Gyirong Port. The report notes that the corridor is characterized by complex geological structures, intense neotectonic activity, pronounced hydroclimatic variations, intensive glacial activity and widespread debris-flow hazards. More than 700 debris-flow gullies have developed along the corridor. The study analyses debris-flow distribution, classifying events into rainfall-induced debris flows, glacial debris flows and glacial lake outburst flood (GLOF)-induced debris flows, and examines the geological, topographic, climatic and glacial conditions that contribute to their occurrence.

This study establishes a debris-flow hazard assessment indicator system using sediment-source, energy-related and triggering factors, and evaluates 1,021 small watershed catchments along the corridor using grey relational analysis and the Jenks natural breaks method. The findings show that high-hazard debris-flow gullies are concentrated in the Gyirong Zangbo basin south of Gyirong County and north of Nyalam County, while high-risk road sections are concentrated in the southern part of Gyirong County, the Xaitongmoin-Lazi section and the Qushui-Shigatse section. The report concludes that widespread glaciers, glacial lakes, moisture transport corridors, steep terrain and fractured rock masses create favourable conditions for debris flows. The findings provide a scientific basis for post-disaster recovery and reconstruction, and support the development of transboundary multi-hazard early warning systems, disaster risk management along transport corridors and bilateral disaster risk reduction cooperation between China and Nepal.