The 2020 glacial lake outburst flood at Jinwuco, Tibet: causes, impacts, and implications for hazard and risk assessment

Abstract

Abstract. We analyze and reconstruct a recent Glacial Lake Outburst Flood (GLOF) process chain on 26 June 2020, involving the moraine-dammed proglacial lake Jinwuco (30.356° N, 93.631° E) in eastern Nyainqentanglha, Tibet, China. Satellite images reveal that from 1965 to 2020, the surface area of Jinwuco has expanded by 0.2 km2 (+56 %) to 0.56 km2, and subsequently decreased to 0.26 km2 (‒54 %) after the GLOF. Estimates based on topographic reconstruction and sets of published empirical relationships indicate that the GLOF had a volume of 10 million m3, an average breach time of 0.62 hours, and an average peak discharge of 5,390 m3/s at the dam. Based on pre- and post-event high-resolution satellite scenes, we identified a large progressive debris landslide originating from western lateral moraine, having occurred 5–17 days before the GLOF. This landslide was most likely triggered by extremely heavy, south Asian monsoon-associated rainfall in June. The time lag between the landslide and the GLOF suggests that pre-weakening of the dam due to landslide-induced outflow pushed the system towards a tipping point, that was finally exceeded following subsequent rainfall, snowmelt, a secondary landslide, or calving of ice into the lake. We back-calculate part of the GLOF process chain, using the GIS-based open source numerical simulation tool r.avaflow. Two scenarios are considered, assuming a debris landslide-induced impact wave with overtopping and resulting retrogressive erosion of the moraine dam (Scenario A), and retrogressive erosion due to pre-weakening of the dam without a major impact wave (Scenario B). Both scenarios yield plausible results which are in line with empirically derived ranges of peak discharge and breach time. The breaching process is characterized by a slower onset and a resulting delay in Scenario B, compared to Scenario A. Evidence, however, points towards Scenario B as a more realistic possibility. There were no casualties from this GLOF but it caused severe destruction of infrastructure (e.g. roads and bridges) and property losses in downstream areas. Given the clear role of continued glacial retreat in destabilizing the adjacent lateral moraine slopes, and directly enabling the landslide to deposit into the expanding lake body, the GLOF process chain under Scenario B can be robustly attributable to anthropogenic climate change, while downstream consequences have been enhanced by the development of infrastructure on exposed flood plains. Such process chains could become more frequent under a warmer and wetter future climate, calling for comprehensive and forward-looking risk reduction planning.

Progress and challenges in glacial lake outburst flood research (2017–2021): a research community perspective

“…Tens of individual GLOF events have been reported since 2017 in different parts of the world including the Hindu Kush-Karakoram-Himalaya (Byers et al, 2019;Yin et al, 2019;Khan et al, 2021;Maharjan et al, 2021;Muhammad et al, 2021), the Tien Shan (Dayirov and Narama, 2020), the Tibetan Plateau (Zheng et al, 2021b), the Tropical Andes (Vilca et al, 2021;Emmer et al, 2022), the Southern Andes (Anyia et al, 2020;Vandekerkhove et al, 2021), the European Alps (Troilo, 2021;Ogier et al, 2021;Stefaniak et al, 2021), Alaska (Kienholz et al, 2020;Abdel-Fattah et al, 2021), British Columbia (Geertsema et al, 2022), Greenland (Tomczyk et al, 2021) and Scandinavia (Andreassen et al, 2022). Recently, Veh et al (2022) compiled globally by far the most complete GLOF inventory (total of >2800 GLOFs until March 2022; available from http://glofs.geoecology.…”

“…On a local scale, a recent trend goes towards better understanding of controls, preconditions and triggers of individual GLOFs and interactions during them (Carrivick et al, 2017;Blauvelt et al, 2020;Vilca et al, 2021), also considering the role of climate and climate change (Zheng et al, 2021b). Numerous studies not only describe, analyse and model the hydrodynamics and geomorphological imprints of GLOFs (e.g.…”

Brief communication: An approximately 50 Mm3 ice-rock avalanche on 22 March 2021 in the Sedongpu valley, southeastern Tibetan Plateau

“…Cryospheric hazards occur frequently in the monsooninfluenced Himalayas, including the southeastern Tibetan Plateau (Kääb et al, 2021;Zheng et al, 2021), a region which hosts temperate glaciers that are typically more sensitive to changes in air temperature than continental glaciers on the Plateau interior (Wang et al, 2019). The region has undergone accelerated mass loss and areal reduction of glacier extent in the past two decades (Bolch et al, 2019), and the rate of regional atmospheric warming is above the global average (Yao et al, 2019).…”

“…The region has undergone accelerated mass loss and areal reduction of glacier extent in the past two decades (Bolch et al, 2019), and the rate of regional atmospheric warming is above the global average (Yao et al, 2019). The southeastern Tibetan Plateau contains high topographic relief conducive for the development of hazard cascades, and the region has experienced a series of high-magnitude ice-rock avalanches, glacier detachments, and glacial lake outburst floods in recent decades (Tong et al, 2019;Veh et al, 2020;Kääb et al, 2021;Zheng et al, 2021). Furthermore, the region is the focus of consid-erable investment by the Chinese government, including the construction of the high-speed Sichuan-Tibet railway (anticipated completion 2030) and the development of adjacent areas along this emerging economic corridor, which links the cities of Lhasa and Chengdu (Fig.…”

Glacial lake outburst flood hazard under current and future conditions: first insights from a transboundary Himalayan basin

“…Finally, all three lakes are susceptible to instantaneous or progressive landslides occurring from the adjacent lateral moraines, most notably for Jialongco where active instabilities are clearly evident. Recent studies have shown that large lateral failures, either instantaneous or progressive, can be sufficient 345 to initiate catastrophic process chains where dam geometries are sufficiently prone to erosion (Klimeš et al, 2016;Zheng et al, 2021b).…”