Numerical simulation of the Qulong Paleolandslide Dam event in the late pleistocene using the finite volume type shallow water model

The Qulong paleolandslide dam event lies in the Benzilan-Batang zone of the upper Jinsha River. The Jinsha River is one of the most extensive water resources in southwest China. Here, the geological environment is complex, and the tectonic activity is intense. Thus, landslide dam events occur frequently, forming large barrier lakes. Analyzing and understanding these events is vital to ensure the safe development and utilization of land and water resources in the Jinsha River valley. In this study, the Qulong paleolandslide dam event, which formed a large barrier lake, is analyzed in detail. The topographic and grain-size analyses of the barrier lake's Qulong gully and lacustrine sediments imply that the Qulong paleolandslide occurred during the last interglacial period. The instability of moraine in the source area caused the landslide dam event that forms a rapid landslide and then transformed into a high-speed clastic flow. Historical data indicate that more than 90% of barrier lakes along the Jinsha are earthquake-triggered landslides, so the relationship between magnitude and epicenter distance of earthquake that induced the Qulong paleolandslide are calculated by Newmark method. The SFLOW software has been used to examine the post-failure evolution and movement characteristics of the Qulong paleolandslide. The results show that the speed of clastic flow reaches 41 m/s or so, and the clastic flow blocks the ancient Jinsha River channel whose thickness reaches 100 m or so, the largest up to 111 m, and its length is more than 4.5 km. Moreover, the high-speed clastic flow runs over the front of the Yinduba platform.