Flood assessment and early warning of the reoccurrence of river blockage at the Baige landslide

Abstract

On 10th Oct. and 3rd Nov. 2018, two successive landslides occurred in the Jinsha River catchment at Baige Village, Tibet Autonomous Region, China. The landslides blocked the major river and formed the barrier lake, which finally caused the huge flood disaster loss. The hillslope at Baige landslide site has been still deforming after the 2018 slidings, which is likely to fail and block the Jinsha River again in the future. Therefore the investigation of 2018 flood disaster at the Baige landslide is of a great significance to provide a classic case for flood assessment and early warning for the future disaster. The detailed survey revealed that the outstanding inundations induced bank collapse disasters upstream the Baige landslide dams, and the field investigations and hydrological simulation suggested that the downstream of the Baige landslide were seriously flooded due to the two periods of the outburst floods. On these bases, the early warning process of potential outburst floods at the Baige landslide was advised, which contains four stages: Outburst Flood Simulating Stage, Outburst Flood Forecasting Stage, Emergency Plan and Emergency Evacuation Stage. The study offers a conceptual model for the mitigation of landslides and flood disasters in the high-relief mountainous region in Tibet.

Primary and potential secondary risks of landslide outburst floods

“…The volume calculation appeared distinct differences between different scholars even in the failed Baige landslide events (Fan et al 2020;Xu et al 2018;Gao et al 2021). Fan and Xu et al (Fan et al 2020;Xu et al 2018) calculated the Baige landslide volume to be ~ 30.0×10 6 m 3 in the first and 12.0×10 6 m 3 in the second by superposing estimated topography before and after failure; Chen et al ) calculated the volumes to be 27.0×10 6 m 3 in the first and 8.0×10 6 m 3 in the second also using topographic superposition methods; Chen and Gao et al Gao et al 2021) calculated the volumes to be 18.7×10 6 m 3 in the first and 6.3×10 6 m 3 in the second using field measurements and before and after topographic superposition methods. The potential deformation range and unstable zones of the Baige landslide themselves have also differed according to the methods adopted (Fan et al 2020;.…”

“…These data have a spatial resolution of 5 m and were obtained from the Geographical Survey Institute of Japan. Finally, discharge data were provided from the Batang gauging station in the Jinsha River (Figure 3), providing reliable real-time monitoring data (Gao et al 2021;. A peak discharge of 20900 m 3 s -1 was recorded during the second flood (Figure 3).…”

“…The dam heights were 47m and 72m, and the subsequent lake that formed extended 45km and 70km and the peak storage capacity reached 0.29x10 9 m 3 and 0.58x10 9 m 3 . There was significant infrastructure damage and the whole of Boluo Town was inundated Gao et al 2021;Xiong et al 2020). With the dam break, the river discharge increased to 10000 m 3 s -1 and 31000 m 3 s -1 respectively.…”

“…This work has struggled to quantify post-flood impacts using remote sensing , notably because of poor image quality. The one-dimensional HEC-RAS hydraulic model has been used to simulate the flood (Fan et al 2020;Gao et al 2021), but its precision is insufficient because it relies on cross-section density and struggles to reproduce spatial patterns of inundation when there is substantial flux of water on the floodplain rather than in the channel. Improvements in hydraulic modelling are needed, not least to allow better assessment of inundation patterns in two dimensions.…”

Seismic Monitoring and Geomorphic Impacts of the Catastrophic 2018 Baige Landslide Hazard Cascades in the Tibetan Plateau

“…On 10 October and 3 November 2018, two successive landslides in the Tibetan plateau (Figure 1a; Zhang, Xiao, et al, 2019;Zhong et al, 2020;Fan, Yang, et al, 2020;Gao et al, 2021;Chen et al, 2021) blocked the Jinsha River, which is the upper course of the Yangtze River, and created two LDLs. The subsequent dam breaches resulted in massive outburst floods that caused the immediate evacuation of >120,000 people (NDRCC, 2018b(NDRCC, , 2018a and severe damage/destruction of 27,000 houses, 8 bridges, 4 hydropower plants, and 33,000 ha of farmland up to 670 km downstream (Chen et al, 2021;Fan, Yang, et al, 2020;Gao et al, 2021;Zhang, Xiao, et al, 2019;Zhong et al, 2020). The second landslide lake outburst flood (LLOF), with peak discharge of ∼31,000 m 3 /s and volume of 5.8 × 10 8 m 3 (Chen et al, 2021;Fan, Yang, et al, 2020;Gao et al, 2021;Zhong et al, 2020), is the largest recorded LLOF of the 21st century to date and provides a unique opportunity to understand such hazard cascades.…”