The largest outburst flood from the Paleo Hutiao Gorge landslide dam, Yangtze River since Late Pleistocene

Abstract

Dam outburst floods caused by the breaching of natural landslide dams are highly destructive catastrophes in the world, far exceeding in magnitude of the gauged flood events. However, reconstructing paleo dammed lake outburst floods remains challenging. In this paper, a comprehensive field survey of the lake and flood deposits upstream and downstream of the paleo landslide dam at Hutiao Gorge, Yangtze River, and spanning 2000 km was conducted, and the chronological evidence suggested that the paleoflood occurred around 30 ka BP. The hydrodynamic model simulated the flood propagation throughout the 2000 km downstream reach. The modeled peak discharge of the dam break was about 7.5 × 10⁵ m³/s and dually verified by the field evidence, which was approximately 90 times of the largest gauged floods in the same reach and was the largest flood in the Yangtze River basin since the Late Pleistocene. The peak discharge attenuated to the largest gauged flood 1800 km downstream. Our research methods offered substantial advantages in reducing uncertainty associated with paleo landslide dam outburst flood estimates, thus enhancing our understanding of outburst mechanisms and aiding in the development of risk analysis for outburst flood events.