Abstract
Glacial lake outburst floods (GLOFs) is one of the main natural disasters in alpine areas, which can cause extreme destruction to downstream settlements and infrastructures. A moraine-dammed lake named JiwenCo glacial lake (JGL) in the southeastern Qinghai-Tibetan Plateau failed on 26 June 2020, destroying many buildings, roads, bridges, and farmlands along the flow path. We reconstructed the process of this GLOF event by the Hydrological Engineering Center’s River Analysis System (HEC-RAS) and examined the JGL’s evolution (area, length, and volume) before its outburst, based on the measured cross sections and hydrological data, videos, and pictures taken by inhabitants, DEM data, and Landsat Thematic Mapper (TM)/Enhanced Thematic Mapper (ETM+)/Operational Land Imager (OLI) images. The result showed that area, length, and volume of the JGL increased by 0.20 ± 0.07 km2, 0.66 ± 0.03 km, and 0.03 ± 0.001 km3 from 1988 to 2020 (before the outburst), respectively. Approximately 0.05 km3 of water volume was discharged with the dropped water level of 15.63 m after the outburst. The peak flow was 534.4 m3/s at breach and increased to 1,408.11 m3/s at Zhongyu town. The difference between the simulated and measured peak flows in Zhongyu town was 41.88 m3/s (3.53%), showing the high accuracy of the modeling results. For villages along the river-channel, the highest velocity was found in Yiga village (14.23 m/s) and the lowest was in Gongwa village (1.22 m/s). The maximum depth was gradually increased as the river reached downstream, 8.03 m in Yiga village and 50.96 m in Duiba village. The combination of landslide, high temperature, and extremely heavy precipitation resulted in this GLOF disaster. An integrated disaster prevention and mitigation plan needs to be developed for susceptible areas such as Niduzangbo basin that experienced two GLOFs in recent 10 years.
Highlights
The Qinghai-Tibetan Plateau has the largest amount of snow and ice around the world, except for the North and South Pole (Yao Tandong et al, 2012)
This study focuses on the JiwenCo glacial lake (JGL) outburst flood recently occurred in southeastern Qinghai-Tibetan Plateau and aims to 1) quantify the evolution of JGL before the outburst; 2) simulate the peak flow and its travel-time at breach and downstream villages after the dam broke; 3) reconstruct the depth, TABLE 1 | The information of the images used in this study
JGL has undergone a dramatic expansion toward its mother glacier in the past 30 years (Figure 5); this evolution pattern is similar to the most moraine-dammed glacial lakes in this basin, such as the RanzeriaCo glacial lake (Sun et al, 2014)
Summary
The Qinghai-Tibetan Plateau has the largest amount of snow and ice around the world, except for the North and South Pole (Yao Tandong et al, 2012). China’s Tibet Autonomous region is a high incidence area of GLOFs, which witnessed 27 glacial lake outbursts since 1960 (Yao et al, 2014; Jia and Cui, 2020). These GLOFs caused severe damages to infrastructures and people’s lives and property in downstream areas. The outburst flood from the Decoga glacial lake, which is located at the Shannan region of Tibet Autonomous region, washed away 18 bridges and killed two people on 18 September 2002 (Tong et al, 2019). The RanzeriaCo glacial lake broken up on 5 July 2013, which outburst flood washed away 49 buildings and caused the economic loss of 0.27 billion CNY (Sun et al, 2014)
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