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Article

An Analysis of the Mechanisms Involved in Glacial Lake Outburst Flooding in Nyalam, Southern Tibet, in 2018 Based on Multi-Source Data

1
National Institute of Natural Hazards, Ministry of Emergency Management, Beijing 100085, China
2
College of Water Conservancy and Civil Engineering, Tibet Agriculture and Animal Husbandry University, Linzhi 860000, China
3
Water Cycle Monitoring Station of Yarlung Zangbo Grand Canyon, Linzhi 860000, China
4
Tibet Autonomous Region Institute of Water Conservancy and Electric Power Planning, Survey and Design Institute, Lhasa 850000, China
*
Author to whom correspondence should be addressed.
Remote Sens. 2024, 16(15), 2719; https://doi.org/10.3390/rs16152719
Submission received: 11 June 2024 / Revised: 23 July 2024 / Accepted: 23 July 2024 / Published: 24 July 2024
(This article belongs to the Section Earth Observation for Emergency Management)

Abstract

Glacial Lake Outburst Flood (GLOF) events, particularly prevalent in Asia’s High Mountain regions, pose a significant threat to downstream regions. However, limited understanding of triggering mechanisms and inadequate observations pose significant barriers for early warnings of impending GLOFs. The 2018 Nyalam GLOF event in southern Tibet offers a valuable opportunity for retrospective analysis. By combining optical and radar remote sensing images, meteorological data, and seismicity catalogs, we examined the spatiotemporal evolution, triggering factors, and the outburst mechanism of this event. Our analysis reveals a progressive retreat of 400–800 m for the parent glaciers between 1991 and 2018, increasing the runoff areas at glacier termini by 167% from 2015 to 2018 and contributing abundant meltwater to the glacial lake. In contrast, the lake size shrunk, potentially due to a weakening moraine dam confirmed by SAR interferometry, which detected continuous subsidence with a maximum line-of-sight (LOS) rate of ~120 mm/a over the preceding ~2.5 years. Additionally, temperature and precipitation in 2018 exceeded the prior decade’s average. Notably, no major earthquakes preceded the event. Based on these observations, we propose a likely joint mechanism involving high temperatures, heavy precipitation, and dam instability. An elevated temperature and precipitation accelerated glacial melt, increasing lake water volume and seepage through the moraine dam. This ultimately compromised dam stability and led to its failure between 3 August 2018 and 6 August 2018. Our findings demonstrate the existence of precursory signs for impending GLOFs. By monitoring the spatiotemporal evolution of environmental factors and deformation, it is possible to evaluate glacial lake risk levels. This work contributes to a more comprehensive understanding of GLOF mechanisms and is of significant importance for future glacial lake risk assessments.
Keywords: GLOF; remote sensing; glacial lake; InSAR; Himalaya GLOF; remote sensing; glacial lake; InSAR; Himalaya

Share and Cite

MDPI and ACS Style

Zhao, Y.; Jiang, W.; Li, Q.; Jiao, Q.; Tian, Y.; Li, Y.; Gong, T.; Gao, Y.; Zhang, W. An Analysis of the Mechanisms Involved in Glacial Lake Outburst Flooding in Nyalam, Southern Tibet, in 2018 Based on Multi-Source Data. Remote Sens. 2024, 16, 2719. https://doi.org/10.3390/rs16152719

AMA Style

Zhao Y, Jiang W, Li Q, Jiao Q, Tian Y, Li Y, Gong T, Gao Y, Zhang W. An Analysis of the Mechanisms Involved in Glacial Lake Outburst Flooding in Nyalam, Southern Tibet, in 2018 Based on Multi-Source Data. Remote Sensing. 2024; 16(15):2719. https://doi.org/10.3390/rs16152719

Chicago/Turabian Style

Zhao, Yixing, Wenliang Jiang, Qiang Li, Qisong Jiao, Yunfeng Tian, Yongsheng Li, Tongliang Gong, Yanhong Gao, and Weishou Zhang. 2024. "An Analysis of the Mechanisms Involved in Glacial Lake Outburst Flooding in Nyalam, Southern Tibet, in 2018 Based on Multi-Source Data" Remote Sensing 16, no. 15: 2719. https://doi.org/10.3390/rs16152719

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