Basic Characteristics and Proneness Evaluation About Debris Flow in Zhangmu Gully of Tibet

Liu Daxiang, Tong Biao, Yang Yueshu, Yao Xiaoyue, Ding Yu, Xia Zhenyao
Zhangmu port, which is the only inland trade port in Tibet, plays an important role in communication between China and Nepal. Debris flow in Zhangmu gully, which is located 1km upstream of the port, would destroy a parking lot, gas station and the China-Nepal road should it occur. Through field investigation on 15 August 2015, section division characteristics of the gully, types and distribution of solid materials, water source situation and some other formation conditions about debris flow
more » ... out debris flow were analysed. According to debris flow reconnaissance specifications suitable for Southwest China, the peak flux of debris flow was estimated using an investigation method and empirical formula, respectively. The estimation indicates that parameters of the debris flow under the situation of a 20-year frequency are most suitable for engineering a design for hazard mitigation. In order to further determine the proneness of debris flow, slope gradient, vegetation coverage, basin area and 12 other parameters were chosen for quantifiable and fuzzy comprehensive evaluation, respectively. Although the proneness belongs to a type of slight according to quantifiable scores and fuzzy membership grade, it is still necessary to take hazard mitigation measures as soon as possible since the proneness shows a tendency from slight to moderate. Moreover, investigation data of water flux at different gully cross-sections with different altitudes indicate that adequate water in the gully may be an important supply source of ground water to the Zhangmu ancient landslide mass. This phenomenon needs to be focused on since it is a disadvantage to the stability of the landslide mass.