Geomorphic effects of debris flows in high mountain areas of the Parlung Zangbo basin, southeast Tibet under the influence of climate change [气候变化影响下藏东南帕隆藏布流域高山区泥石流的地貌效应]

作者：Yu G.; Lu J.; Li Z.; Hou W.

来源：Acta Geographica Sinica, 2022, 77(3): 619-634.

DOI：10.11821/dlxb202203009

• Debris flow
• Geomorphic effect
• High mountains
• Long-term evolution
• Southeast Tibet

High altitude or high latitude mountain areas, especially alpine glaciers and rapidly shrinking permafrost regions, provide suitable topography and material source for the development of debris flow. Under the influence of climate change, such as rising temperature and increasing heavy rainfall events, the potential hazard inducing environment of alpine regions is more likely to trigger hazards. As an important natural hazard and mass flow type, debris flow has become an important driving force of geomorphologic evolution in alpine regions. However, few research reported debris flow processes and its geomorphologic effects in alpine regions due to the difficulty of field monitoring and lack of data. We first analyzed the morphologic effects of alpine debris flow based on a case study on the Parlung Zangbo basin (with three typical debris flow prone gullies, i.e., Zhamunong, Guxiang and Tianmo), located in southeast Tibet, where debris flow occurs frequently. Combined with remote sensing image, DEM data, UAV aerial photography, high-accuracy survey of RTK and field recording, the geomorphic development characteristics of debris flow gully (such as erosion-deposition variation and wandering) and its influence on river morphology of main channels were analyzed. The long-term evolution of river valley morphology under the influence of large-scale debris flow events was also discussed. The debris flow processes in alpine regions strongly shaped gully morphology. The upstream gully channel is eroded and expanded strongly, and the erosion-deposition variation of debris flow deposited fan is determined by the scale of debris flow events and flow intensity. Debris flows significantly affect the river morphology of a main channel, which lead to lateral scouring/silting and wandering of the main channel, and affect the planform channel pattern development of upstream of the landslide dam. In the long term, the river valley morphology would evolve into a wide and narrow alternating planform and a stair-case like longitudinal profile.

• 单位
  中国科学院大学; 水资源与水电工程科学国家重点实验室