Formation and breach of the giant Cuola landslide dam and their impacts on the landscape evolution of river valley in the Jinsha River, southeastern Tibet

Abstract

The giant Cuola landslide is one of the largest and highest landslide dams in the upper reaches of the Jinsha River, which brought about a substantial influence on the geomorphological evolution of the Jinsha River valley. Through field investigations, UAV photogrammetry, OSL, and ¹⁰Be dating methods, the topographic and geological characteristics of the Cuola landslide dam were examined, and the evolution features of formation and failure were investigated as well. The results indicate that the Cuola landslide, with a volume of ~ 4 × 10⁸ m³ and an age of ~ 50.9 ka BP, was primarily due to a seismic event, and the major failure mode of the ~ 1590-m-high source area on the left bank was attributable to a wedge sliding. The landslide body slid into the valley and climbed ~ 540 m up the right bank with a long runout of 3740 m. The relict landslide deposits demonstrate a large-scale natural dam with a height of 272 m, a length of 1780 m, and a width of 1940 m, which completely blocked the river, and formed a dammed lake with an inundation length of 190 km and an impoundment volume of 10.817 km³. The longevity of the landslide dam was discussed in terms of glacial climate, dam morphology, and material characteristics, and fault dislocation was deduced to induce the overtopping dam break at ~ 4 ka BP. The overflowing water preferentially undercut the weak zone created by fault displacement within the dam until the onset of the final breach, facilitated by the warm climatic conditions of Holocene Climatic Optimum. The findings in this study illustrate the dramatic longevity of a natural dam produced by a giant landslide in one of the most deeply incised valleys in the world and provide a conceptual model for a better understanding of landslide-induced landscape evolution of high-relief river catchments.