Dam-break dynamics at Huohua Lake following the 2017 Mw 6.5 Jiuzhaigou earthquake in Sichuan, China

Jiuzhaigou County in Sichuan, China is renowned for its beautiful natural scenery, recognized as a World Heritage Site and World Biosphere Reserve by the UNESCO. On August 8, 2017, a M-s 7.0 (M-w 6.5) earthquake struck the region, causing severe damage and casualties. The earthquake triggered thousands of landslides and the collapse of the natural travertine dam impounding Huohua Lake, an important tourist attraction in the reserve. In this study, the dam failure process was investigated through field surveys and remote sensing observations. The propagation of the flood surge was analyzed by Massflow, a depth-integrated continuum model based on the MacCormack-TVD finite difference algorithm. The model results were validated against vegetation maps evaluated from satellite multispectral data recorded before and after the event. The relation between changes in vegetation coverage and computed flooded areas, flow depth, and velocities was elucidated. This study is preliminary in nature, yet the proposed approach could be used, after further validation, in flood hazard and vegetation damage assessments, which may be especially valuable in nature reserves.