First World Congress of International Consortium on Geo-disaster Reduction (1st ICGdR World Congress)

Ancient mega-landslide damming events in southwestern Tibetan Plateau remain insufficiently identified and investigated. This study examines the previously unreported Nuba mega-landslide on the right bank of the Xiangquan River gorge. Field investigation, laboratory analyses, UAV topographic survey, optically stimulated luminescence (OSL) dating and SBAS-InSAR monitoring were integrated to characterize the morphology of the Nuba landslide, assess its geomorphic and human-environmental impacts on the Zhada Basin, and evaluate its present-day activity. The Nuba landslide covers 31.7 km² with a volume between 7.4 and 19.9 km³. The landslide boundary morphology was constrained by the Dongbarang-Gongbu fault, and its failure mode is creep-induced tensile cracking controlled by a hard-over-soft lithological configuration. OSL ages indicate that the Nuba landslide-dammed lake persisted from the Late Pleistocene to the Holocene. As lake level declined due to overtopping erosion, potentially cultivable land within the basin increased by up to 295%, probably promoting the migration of human settlements from basin-margin uplands toward the basin interior from the prehistoric period through the Zhangzhung and Guge periods. The youngest shoreline of the landslide sag pond yielded an age of 0.39 ± 0.04 ka BP, which records the final failure of the residual landslide dam. Modern SBAS-InSAR results indicate that the rear part of the Nuba landslide remains locally active, with a maximum LOS displacement rate of -31.37 mm/a. This study provides a key case for understanding the links among late Quaternary basin evolution, human settlement responses to giant landslide-dammed lakes, and modern geohazard risk on the southwestern Tibetan Plateau.

River-damming landslide,Tibetan Plateau,Zhada Basin,Landform response