Chronology and evolution process of the Zhaizicun ancient landslide-dammed lake in the middle reaches of the Jinsha River, southwest China

Floods caused by landslide dam failure are destructive natural disasters that threaten downstream lives and property. The Jinsha River, located on the southeastern margin of the Tibetan Plateau, contains numerous large-scale paleo-landslides and river-blocking events, which provide important information for studying regional tectonic activity, paleoenvironmental changes, and landscape evolution. For these paleo-landslide-dammed lakes along the Jinsha River, their formation time, dynamic processes, and evolution of paleolake outburst have not been clearly clarified, requiring in-depth targeted research. This study focuses on the Zhaizicun paleo-dammed lake in the Taoyuan section in the middle reaches of the Jinsha River. The chronology of this giant paleo-landslide-dammed lake is controversial, and its evolutionary process has not been fully reconstructed. Optically stimulated luminescence (OSL) dating, paleolake reconstruction and dam-breach flood simulations were employed to resolve these issues. The research results are as follows: (1) OSL ages suggests that this paleo-dammed lake formed around 59.9 ka. (2) Based on the DEM data, reconstruction analysis of this lake via ArcGIS shows its maximum surface area of about 1.38×10⁸m² and storage capacity of approximately 5.6×10⁹m³. (3) The dam breach occurred approximately 32.5 ka, using the DB-IWHR and HEC-RAS models, the peak flood discharge was estimated at around 109, 702 m³/s. Within the simulated area (from Taoyuan to Panzhihua), the flood inundated a maximum area of 141.7 km² after 25 hours, with a maximum water depth of 89.5 m and a peak velocity of 24.1 m/s. These findings provide important insights into high-energy outburst floods and support the development of more effective disaster prevention and mitigation strategies in the region.