Debris Flows along the China-Nepal Highway
西藏中尼公路沿线的泥石流

The China-Nepal Highway, located in southwest Tibet, is vital not only to the eco-nomical development of Tibet, but also to national defense in China. Because of the complexof geologic structures, complicated stratigraphic and lithologic characters, intensive neotecton-ic movememts, a great variety of hydrothermal condtions and strong glacial actions, all kindof natural hazads occur widely on both sides of the highway, such as debris flows, land-slides, avalanches, etc. The above hazards often threaten the transportaion safety of the high-way, and severly restrict local economic development. Among all the mountain hazards, de-bris flow is the major one. In this paper, based on historical data, the interpretation of aerialphotos and satellite images (TM and SPOT), as well as field investigation, the environmentalbackground of the study area, especially the geological structure, 1ithology, plant and soil, hy-drography and climate are analyzed in detail. Some 842 debris flow gullies are identified inthis area, of which 474 have clear channels and 24l develop on both sides of the highway.The mouths of debris flow gullies are located at elevations between l8l0 m and 5000 m, ofwhich more than 80% range between 3500 m and 4500 m. The drainage basins of debris flowgullies cover an area between 0.2-l6l km2, especially, 75% of which with an area betweenl.0-5.0 km2. According to their genesis, debris flows in this area can be divided into 3 types:glacia1, glacial lake burst and rainfall. Of the 24l debris-flow gullies, 205 (85.1%) are of rain-fall debris flows and 26 (l0.8%) are of glacial debris flows.