New insights into the occurrence of the Baige landslide along the Jinsha River in Tibet

The catastrophic Baige landslide occurred on October 10, 2018 in the Tibet Autonomous Region, China, and formed a barrier lake with a direct economic loss of 6.8 billion RMB (~ 963.5 million USD). After the landslide, field investigations were conducted both to support emergency operations and to understand the failure mechanism immediately after the landslide. Detailed field surveys, borehole exploration, discharge measurements, laboratory experiments, and meteorological analyses were employed in this study to explore the mechanisms underlying the Baige landslide. A key influence from the water source in Bogong Gully on the Baige landslide formation was newly found. The results show that the underground of the slope comprises extremely weathered serpentinite, and fresh rock has not yet been revealed in boreholes. The seepage outlets are 450–550 m higher than the Jinsha River and ~ 118 m lower than the bed of Bogong Gully. Water flow in the channel of Bogong Gully is strongly infiltrated, with a flow loss of 62.6%. Seepage into the Bogong Gully, along with the landslide, caused by the local geological structure and lithology, accelerated the extreme weathering of rock masses and promoted landslide formation. Furthermore, extreme annual rainfall also contributed to the occurrence of the Baige landslide by increasing the discharge of the Bogong Gully. Further risk management measures in this area should include increasing the depth of geological explorations and the construction of drainage systems.