Characteristics and evolution process simulation of the Baqu gully debris flow triggered by ice-lake outburst in Luolong County of Tibet, China

Abstract

The Baqu glacial lakes outburst debris flow is close to a station of the Sichuan-Tibet Railway, which may threaten the construction and running of the railway. In this paper, the methods of in-site investigation and remote sensing were used to identify the basic geological characteristics of the Baqu gully. The kinetics parameters of debris flow were calculated by using the code-design-formulae method. Meanwhile, the stability of barrier dams of 7 glacial lakes in Baqu was evaluated based on the dimensionless blockage index (DBI). The results show that the DBI value of the 1# barrier dam was in the unstable region, and the DBI value of the 3#, 4# and 6# barrier dams were between the unstable region and the stable region, and there was a possibility of outburst. In this paper, we used RAMMS, a single-phase flow numerical method, to simulate and analyse the evolution process of glacial lakes outburst in the Baqu gully under 4 scenarios. The simulation results show that the evolution process is divided into 4 stages: initiation, confluence, runout and deposition, which lasted for 4.5 hours. The results also show that the maximum velocity, depth and discharge of the debris flow at the mouth of the channel were 5.92 m/s, 4.35 m and 1 954.42 m3/s (5.1 times of that of the rainstorm debris flow), respectively, under the condition of glacial lake 1#—4# and 6# outburst. In addition, the influence area of outburst flood in 4 scenarios affected the proposed station, and the maximum depth was 1.91 m, 3.36 m, 1.53 m and 4.35 m, respectively. Therefore, in the design of the station, it is necessary to take engineering measures such as drainage canal or diversion dike for protection and treatment, so as to ensure the safe running of the station. The above results can provide reference for the line selection of the Sichuan-Tibet Railway and the prevention and control of glacial lakes outburst debris flow in the Eastern part of the Qinghai-Tibet Plateau.

Keywords

• sichuan-tibet railway
• glacier-lake debris flow
• dimensionless blockage index (dbi)
• ramms
• outburst evolution process