Glacial Lake Outburst Floods Events Research Articles

Altimetry-based ice-marginal lake water level changes in Greenland

Greenland holds over 3300 ice-marginal lakes, serving as natural reservoirs for outflow of meltwater to the ocean. A sudden release of water can largely influence ecosystems, landscape morphology, ice dynamics and cause flood hazards. While large-scale studies of glacial lake outburst floods (GLOFs) have been conducted in many glaciated regions, Greenland remains understudied. Here we use altimetry data to provide the first Greenland-wide inventory of ice-marginal lake water level changes, studying over 1100 lakes from 2003–2023, revealing a diverse range of lake behaviors. Around 60% of the lakes exhibit minimal fluctuations, while 326 lakes have drained, collectively contributing to 541 observed GLOFs from 2008–2022. These GLOFs vary substantially in magnitude and frequency, with the highest concentration observed in the North and Northeast regions. Our results show substantial annual differences in the number of GLOFs with a notable peak in 2019, coinciding with a year marked by extreme runoff. Our method detected a 1200% increase in the number of draining lakes compared to existing historical databases. This highlights a large underreporting of GLOF events and emphasizes the pressing need for a deeper understanding of the mechanisms behind and the consequences of these dramatic events.

Altimetry-based ice-marginal lake water level changes in Greenland

Greenland holds over 3300 ice-marginal lakes, serving as natural reservoirs for outflow of meltwater to the ocean. A sudden release of water can largely influence ecosystems, landscape morphology, ice dynamics and cause flood hazards. While large-scale studies of glacial lake outburst floods (GLOFs) have been conducted in many glaciated regions, Greenland remains understudied. Here we use altimetry data to provide the first Greenland-wide inventory of ice-marginal lake water level changes, studying over 1100 lakes from 2003–2023, revealing a diverse range of lake behaviors. Around 60% of the lakes exhibit minimal fluctuations, while 326 lakes have drained, collectively contributing to 541 observed GLOFs from 2008–2022. These GLOFs vary substantially in magnitude and frequency, with the highest concentration observed in the North and Northeast regions. Our results show substantial annual differences in the number of GLOFs with a notable peak in 2019, coinciding with a year marked by extreme runoff. Our method detected a 1200% increase in the number of draining lakes compared to existing historical databases. This highlights a large underreporting of GLOF events and emphasizes the pressing need for a deeper understanding of the mechanisms behind and the consequences of these dramatic events.

Retrospective Analysis of Glacial Lake Outburst Flood (GLOF) Using AI Earth InSAR and Optical Images: A Case Study of South Lhonak Lake, Sikkim

On 4 October 2023, a glacier lake outburst flood (GLOF) occurred at South Lhonak Lake in the northwest of Sikkim, India, posing a severe threat to downstream lives and property. Given the serious consequences of GLOFs, understanding their triggering factors is urgent. This paper conducts a comprehensive analysis of optical imagery and InSAR deformation results to study changes in the surrounding surface of the glacial lake before and after the GLOF event. To expedite the processing of massive InSAR data, an InSAR processing system based on the SBAS-InSAR data processing flow and the AI Earth cloud platform was developed. Sentinel-1 SAR images spanning from January 2021 to March 2024 were used to calculate surface deformation velocity. The evolution of the lake area and surface variations in the landslide area were observed using optical images. The results reveal a significant deformation area within the moraine encircling the lake before the GLOF, aligning with the area where the landslide ultimately occurred. Further research suggests a certain correlation between InSAR deformation results and multiple factors, such as rainfall, lake area, and slope. We speculate that heavy rainfall triggering landslides in the moraine may have contributed to breaching the moraine dam and causing the GLOF. Although the landslide region is relatively stable overall, the presence of a crack in the toparea of landslide raises concerns about potential secondary landslides. Our study may improve GLOF risk assessment and management, thereby mitigating or preventing their hazards.

Inventory and GLOF susceptibility of glacial lakes in Chenab basin, Western Himalaya

Global warming causes glacial mass loss, leading to the growth of high-mountain glacial lakes. The presence of glacial lakes poses a significant threat to downstream communities, as they can produce destructive Glacial Lake Outburst Floods (GLOFs). Timely basin-scale inventory and GLOF susceptibility assessments are crucial, considering past GLOF events in the Himalayan region. Here, an updated inventory of glacial lakes in the Chenab basin, Western Himalayas was generated based on Sentinel-2 datasets for 2022. We assessed temporal changes and GLOF susceptibility for glacial lakes (>0.05 km2) through a multi-criteria based Analytical Hierarchical Process, classifying them into low, medium, high, and very high susceptibility classes. The results reveal 419 lakes (>0.001 km2; 9.97 ± 0.67 km2) in the basin in 2022. Glacial lakes (>0.05 km2) area increased by ∼75%, from 3.92 ± 0.58 to 6.86 ± 0.25 km2 during 1990–2022. Of the 42 lakes (>0.05 km2) evaluated, four showed very high GLOF susceptibility. The study emphasizes the impact of local geomorphology and glacier-lake interaction under warming climate, likely to increase the GLOF susceptibility in the region. Regular monitoring and detailed fieldwork for these susceptible lakes are crucial for early warning and disaster risk reduction for downstream communities.

Potential threats of glacial lake changes to the Sichuan-Tibet Railway

Abstract The Sichuan-Tibet Railway, China's second inland railway to Tibet, is currently being constructed and will run between Chengdu and Lhasa. It will cross the southeastern Tibetan Plateau and be surrounded by glacial lakes, some of which may pose a threat of glacial lake outburst flood (GLOF) events. Both the specific location and the outburst susceptibility of these glacial lakes are largely unknown. In this study, we mapped the glacial lakes using declassified Corona KH-4 and Hexagon KH-9 from the 1960s and Sentinel-2 imagery from 2020 and assessed their spatio-temporal changes. GLOF-susceptibility criteria were established based on historical GLOF events. The results show that the total area (number) of glacial lakes has increased by 22% (20%) from 126.1 ± 2.4 km2 (1662 lakes) in the 1960s to 153.6 ± 11.1 km2 (1994 lakes) in 2020. Of these lakes, this study identified 38 very high and 85 high GLOF-susceptibility lakes; mainly distributed along the Bomi-Nyingchi railway section in the Parlung Zangbo River basin. Four of the very high GLOF-susceptibility glacial lakes may pose a threat to the railway and will require monitoring. The insights from this study can be used to mitigate the risk of GLOFs during the construction and maintenance of the Sichuan-Tibet Railway.

Reconstructing glacial lake outburst floods in the Poiqu River basin, central Himalaya

The Poiqu River basin in central Himalaya is a transboundary basin between China and Nepal that has experienced rapid glacier ice loss and glacial lake growth, some of which have drained in catastrophic glacial lake outburst floods (GLOFs). Here, we focus on the outbursts of two glacial lakes in this basin, Gongbatongsha Co in 2016, and Poiqu No.1 in 2002, and integrate multiple data sources and approaches to improve our understanding of past GLOFs and project the magnitude of potential future GLOFs. We identify their potential triggers and assess downstream damage by combining remote sensing observations and field surveys. We find that after the outbursts, Gongbatongsha Co shrank by 0.14 ± 0.003 km2 (∼91 %) in 2016 and almost disappeared, and Poiqu No.1 shrank by 0.05 ± 0.001 km2 (∼80 %) in 2002 but then expanded by 0.10 ± 0.002 km2 (∼670 %) by 2022. Our study identifies ice avalanches from the parent glaciers as the dominant trigger of the two GLOF events, and clarifies that the 2002 GLOF event stemmed from Poiqu No.1 instead of the reported Jialong Co. We also reconstructed the flow depths, velocities, and inundation areas using the hydrodynamic models HEC-RAS and FLO-2D. For Gongbatongsha Co, the models suggest that the discharge peaked at ∼550 m3s−1 about 15 min after the outburst, and the flood reached the settlement of Zhangmu with a peak flow of ∼1600 m3s−1 about 8.5 h later. The peak discharge during the GLOF from Poiqu No.1 was ∼2700 m3s−1. The flood reached the town of Nyalam 1.3 h later, with a peak discharge of ∼1100 m3s−1. The simulation of a future GLOF from Poiqu No.1 shows significant potential impacts to Nyalam town and other downstream communities due to the high flow depth. A large GLOF scenario for Poiqu No.1 would result in a peak discharge of more than 2500 m3s−1, with the flood wave reaching Nyalam in less than 40 min. We show that very high-resolution digital elevation models such as obtained from uncrewed aerial vehicles perform better in flood simulation. Our approach can be applied to potentially dangerous glacial lakes in other high mountain areas.

Outbursts from an ice-marginal lake in Antarctica in 1969–1971 and 2017, revealed by aerial photographs and satellite data

The liquid water around the Antarctic Ice Sheet plays a key role in modulating both the vulnerability of ice shelves to hydrofracturing and ice discharge from outlet glaciers. Therefore, it needs to be adequately constrained for precise future projections of ice-mass loss and global sea-level rise. Although glacial lake outburst floods (GLOFs) pose one of the greatest risks in glacierized mountainous regions, any long-term monitoring of Antarctic ice-marginal lakes and their associated potential for GLOFs has been neglected until recently owing to the limited number of such events reported in Antarctica. Here we present direct evidence of repeated GLOFs from Lake Kaminotani-Ike, an ice-sheet-dammed lake in East Antarctica, via an analysis of historical aerial photographs and recent satellite data. Two GLOFs occurred in 1969–1971 and 2017, with discharge volumes of (8.6 ± 1.5) × 107 and (7.1 ± 0.4) × 107 m3, respectively, making them two of the largest GLOFs in Antarctica. A southerly oceanward pathway beneath the ice sheet is the most likely drainage route of these GLOF events based on the available surface- and bed-elevation datasets. Furthermore, the 2017 event occurred during the austral winter, thereby implying the possibility of year-round active subglacial networks in Antarctica. Our results highlight that studies on Antarctic ice-marginal lakes provide an opportunity to better understand Antarctic hydrological processes and emphasize the need for both detailed monitoring of ice-marginal lakes and detailed surveying of the subglacial environments of the Antarctic Ice Sheet.

A generic framework for glacial lake outburst flood investigation: A case study of Zalai Tsho, Southeast Tibet

Glacial lake outburst floods (GLOFs) are one of the most severe natural disasters, resulting in enormous socio-economic losses as well as threatening downstream settlements and infrastructure in the alpine region. Understanding historical GLOFs benefits disaster reduction and landscape conservation, but many GLOF events remain unreported or lack critical attributes. In this study, a novel framework was proposed to detect historical GLOFs and populate related attributes using a combination of Landsat, Sentinel-2 and Planet optical images, Sentinel-1 Synthetic Aperture Radar (SAR) images, field surveys, and documentation. The framework was implemented successfully on the case of Zalai Tsho, which revealed a previously unknown GLOF with critical attributes including the associated lake evolution, the flood process, and the impacts. The Zalai Tsho GLOF event in Bomi County, Southeast Tibet, occurred on July 7, 2018. Zalai Tsho emerged in 1994, and its surface area increased by 178% between 1994 and 2018, followed by a complete disappearance after the dam failure. A total water volume of 2.7 ± 0.2 × 105 m3 was released from Zalai Tsho to generate a peak discharge of 558.4 m3/s estimated by hydrological models, which destroyed a bridge, 23.2 ha of woodland, and 1.7 ha of farmland. The Zalai Tsho GLOF was initiated by intense melting waters, superimposed on water from an upstream supraglacial lake, eventually resulted in serious socio-economic losses and long-term environmental effects. Post-GLOF conservation projects play a positive role in protecting residents against flooding, while soil erosion has been exacerbated in certain areas without artificial countermeasures. This study provided an up-to-date, prototype framework for the identification of historical GLOF events to enrich the GLOF dataset and contributed to the risk assessment of GLOF and landscape conservation.

Causes and effects of Shisper glacial lake outburst flood event in Karakoram in 2022

Karakoram Himalayas are vulnerable to glacial lake outburst floods (GLOFs), which cause catastrophic floods in the surrounding areas. The increasing natural and anthropogenic activities, especially in the Indo-Gangetic Plains at the southern flank of the towering Himalayas, could be the cause of climate change affecting the frequency of the natural hazards in the Himalayas. In the present study, a detailed analysis of the Shisper Lake breach of 7 May 2022 is carried out using satellite remote sensing. A decreasing trend in the glacial mass balance is observed between 2017 and 2021; in this period, frequent GLOF episodes occurred. A pronounced decline in the snow cover and glacial debris (before the cascade) and an abnormal increase in land surface temperature (LST) retrieved from satellite data could be responsible for the enhanced snow/glacial melting prior to the breach. Alteration in glacial mobility (cm/12 days) is observed at the locations where the glacier melts due to an increase in LST with increased debris cover. In the paper, we have studied changes in water quality and land cover along the stream after the GLOF. An increment in normalized difference turbidity index (NDTI) is observed before the flood showing turbulence and sediment load. Increased glacial melt contribution into the stream results in increased flow rate and decreased water quality as observed through normalized difference water index (NDWI) and normalized difference chlorophyll index (NDCI), near the Karakoram Highway Bridge. Sentinel-1 backscatter coefficient indicates increased discharge from the melting of glaciers. A significant reduction in co-flood coherence is observed, attributed to the bridge collapse and severe bank erosion.

A comprehensive and version-controlled database of glacial lake outburst floods in High Mountain Asia

Abstract. Glacial lake outburst floods (GLOFs) have been intensely investigated in High Mountain Asia (HMA) in recent years and are the most well-known hazard associated with the cryosphere. As glaciers recede and surrounding slopes become increasingly unstable, such events are expected to increase, although current evidence for an increase in events is ambiguous. Many studies have investigated individual events, and while several regional inventories exist, they either do not cover all types of GLOF or are geographically constrained. Further, downstream impacts are rarely discussed. Previous inventories have relied on academic sources and have not been combined with existing inventories of glaciers and lakes. In this study, we present the first comprehensive inventory of GLOFs in HMA, including details on the time of their occurrence, processes of lake formation and drainage involved, and downstream impacts. We document 697 individual GLOFs that occurred between 1833 and 2022. Of these, 23 % were recurring events from just three ephemeral ice-dammed lakes. In combination, the documented events resulted in 6906 fatalities of which 906 can be attributed to 24 individual GLOF events, which is 3 times higher than a previous assessment for the region. The integration of previous inventories of glaciers and lakes within this database will inform future assessments of potential drivers of GLOFs, allowing more robust projections to be developed. The database and future, updated versions are traceable and version-controlled and can be directly incorporated into further analysis. The database is available at https://doi.org/10.5281/zenodo.7271187 (Steiner and Shrestha, 2023), while the code including a development version is available on GitHub.

Remote Sensing Monitoring and Analysis of Jinwuco Lateral Moraine Landslide-Glacial Lake Outburst in Southeast Tibet

On 25 June 2020, a glacial lake outburst flood (GLOF) occurred in Jinwuco, Nidou Zangbo, and southeast Tibet, causing catastrophic damage to multiple infrastructures such as roads, bridges, and farmlands in the surrounding and downstream areas. Due to the lack of long-term monitoring of glacial lake and glacier changes in the region and the surrounding surface, the spatial and temporal evolutionary characteristics and triggering factors of the disaster still need to be determined. Here, we combine multi-temporal optical remote sensing image interpretation, surface deformation monitoring with synthetic aperture radar (SAR)/InSAR, meteorological observation data, and corresponding soil moisture change information to systematically analyze the spatial and temporal evolution characteristics and triggering factors of this GLOF disaster. Optical images taken between 1987 and 2020 indicate that the glacial lake’s initial area of 0.39 km2 quickly grew to 0.56 km2, then plummeted to 0.26 km2 after the catastrophe. Meanwhile, we found obvious signs of slippage beside the lateral moraine at the junction of the glacier’s terminus and the glacial lake. The pixel offset tracking (POT) results based on SAR images acquired before and after the disaster reveal that the western lateral moraine underwent a 40 m line of sight (LOS) deformation. The small baseline subset InSAR (SBAS-InSAR) results from 2017 to 2021 show that the cumulative deformation of the slope around the lateral moraine increased in the rainy season before the disaster, with a maximum cumulative deformation of −52 mm in 120 days and gradually stabilized after the disaster. However, there are three long-term deformation areas on the slope above it, showing an increasing trend after the disaster, with cumulative deformation exceeding −30 mm during the monitoring period. The lateral moraine collapse occurred in a warm climate with continuous and intense precipitation, and the low backscatter intensity prior to the slide suggests that the soil was very moist. Intense rainfall is thought to be the catalyst for lateral moraine collapse, whereas the lateral moraine falling into the glacier lake is the direct cause of the GLOF. This study shows that the joint active–passive remote sensing technique can accurately obtain the spatial and temporal evolution characteristics and triggering factors of GLOF. It is helpful to understand the GLOF event caused by the slide of lateral moraine more comprehensively, which is essential for further work related to glacial lake hazard assessment.

Exploring Contrastive Representation for Weakly-Supervised Glacial Lake Extraction

Against the background of the ongoing atmospheric warming, the glacial lakes that are nourished and expanded in High Mountain Asia pose growing risks of glacial lake outburst floods (GLOFs) hazards and increasing threats to the downstream areas. Effectively extracting the area and consistently monitoring the dynamics of these lakes are of great significance in predicting and preventing GLOF events. To automatically extract the lake areas, many deep learning (DL) methods capable of capturing the multi-level features of lakes have been proposed in segmentation and classification tasks. However, the portability of these supervised DL methods need to be improved in order to be directly applied to different data sources, as they require laborious effort to collect the labeled lake masks. In this work, we proposed a simple glacial lake extraction model (SimGL) via weakly-supervised contrastive learning to extend and improve the extraction performances in cases that lack the labeled lake masks. In SimGL, a Siamese network was employed to learn similar objects by maximizing the similarity between the input image and its augmentations. Then, a simple Normalized Difference Water Index (NDWI) map was provided as the location cue instead of the labeled lake masks to constrain the model to capture the representations related to the glacial lakes and the segmentations to coincide with the true lake areas. Finally, the experimental results of the glacial lake extraction on the 1540 Landsat-8 image patches showed that our approach, SimGL, offers a competitive effort with some supervised methods (such as Random Forest) and outperforms other unsupervised image segmentation methods in cases that lack true image labels.

Assessment of potential present and future glacial lake outburst flood hazard in the Hunza valley: A case study of Shisper and Mochowar glacier

In Himalayas, new glacial lake formation and expansion of existing glacial lakes have occurred as a consequence of the increasing temperature and glacier recession. These lakes have the potential to release catastrophic volumes of water and trigger a glacial lake outburst flood (GLOF). GLOFs can cause devastating downstream impacts including loss of lives, damage to infrastructure, and economic loss. The risk associated with GLOFs is evident in the case of the Mochowar and the Shisper glaciers of the Hunza valley in the Karakoram ranges. The present study is divided in two parts: 1) investigation of the recent GLOF event from the Shisper glacier ice-dammed lake on 7th May 2022. 2) identification of an overdeepening site for future lake formation at the Mochowar glacier and its future GLOF susceptibility; We used the Himalayan Glacier Thickness Mapper (HIGTHIM) to calculate the thickness of Mochowar glacier and identify an overdeepening site at its terminus. This site could host a glacial lake of area 0.22 km2 and a mean depth of 58.97 m that can release a potential flood volume leading to cascading effects with the Shisper ice-dammed lake that further increases the GLOF susceptibility. The GLOF susceptibility of this future lake was determined to be high based on a multi-criterion decision analysis. The recent GLOF event of 7th May 2022 occurred from the Shisper glacier ice-dammed lake. We applied a 2D hydrodynamic model for investigating this GLOF episode and estimated a release volume of 6.23 × 106 m3, with a modelled peak discharge of approximately 1505 m3 s−1.

Glacial Lake Outburst Flood Hazard and Risk Assessment of Gangabal Lake in the Upper Jhelum Basin of Kashmir Himalaya Using Geospatial Technology and Hydrodynamic Modeling

Climate warming-induced glacier recession has resulted in the development and rapid expansion of glacial lakes in the Himalayan region. The increased melting has enhanced the susceptibility for Glacial Lake Outburst Floods (GLOFs) in the region. The catastrophic failure of potentially dangerous glacial lakes could be detrimental to human life and infrastructure in the adjacent low-lying areas. This study attempts to assess the GLOF hazard of Gangabal lake, located in the Upper Jhelum basin of Kashmir Himalaya, using the combined approaches of remote sensing, GIS, and dam break modeling. The parameters, such as area change, ice thickness, mass balance, and surface velocity of the Harmukh glacier, which feeds Gangabal lake, were also assessed using multitemporal satellite data, GlabTop-2, and the Cosi–Corr model. In the worst-case scenario, 100% volume (73 × 106 m3) of water was considered to be released from the lake with a breach formation time (bf) of 40 min, breach width (bw) of 60 m, and producing peak discharge of 16,601.03 m3/s. Our results reveal that the lake area has increased from 1.42 km2 in 1972 to 1.46 km2 in 1981, 1.58 km2 in 1992, 1.61 km2 in 2001, 1.64 km2 in 2010, and 1.66 km2 in 2020. The lake area experienced 17 ± 2% growth from 1972 to 2020 at an annual rate of 0.005 km2. The feeding glacier (Harmukh) contrarily indicated a significant area loss of 0.7 ± 0.03 km2 from 1990 (3.36 km2) to 2020 (2.9 km2). The glacier has a maximum, minimum, and average depth of 85, 7.3, and 23.46 m, respectively. In contrast, the average velocity was estimated to be 3.2 m/yr with a maximum of 7 m/yr. The results obtained from DEM differencing show an average ice thickness loss of 11.04 ± 4.8 m for Harmukh glacier at the rate of 0.92 ± 0.40 m/yr between 2000 and 2012. Assessment of GLOF propagation in the worst-case scenario (scenario-1) revealed that the maximum flood depth varies between 3.87 and 68 m, the maximum flow velocity between 4 and 75 m/s, and the maximum water surface elevation varies between 1548 and 3536 m. The resultant flood wave in the worst-case scenario will reach the nearest location (Naranaag temple) within 90 min after breach initiation with a maximum discharge of 12,896.52 m3 s−1 and maximum flood depth and velocity of 10.54 m and 10.05 m/s, respectively. After evaluation of GLOF impacts on surrounding areas, the area under each inundated landuse class was estimated through the LULC map generated for both scenarios 1 and 2. In scenario 1, the total potentially inundated area was estimated as 5.3 km2, which is somewhat larger than 3.46 km2 in scenario 2. We suggest a location-specific comprehensive investigation of Gangbal lake and Harmukh glacier by applying the advanced hazard and risk assessment models/methods for better predicting a probable future GLOF event.

A robust glacial lake outburst susceptibility assessment approach validated by GLOF event in 2020 in the Nidu Zangbo Basin, Tibetan Plateau

As reports on glacial lake outburst floods (GLOFs) have increased with global warming, a robust GLOF susceptibility assessment approach is critical for disaster prevention and damage reduction. A robust GLOF susceptibility assessment approach, using the Analytic Hierarchy Process (AHP) to assess the potential hazard grades of glacial lakes combined with data from a digital elevation model (DEM), glaciers, remote sensing images, and field investigations, was constructed and applied in the Nidu Zangbo Basin in Nagqu, Tibetan Plateau. From 1988 to 2016, the total number and area of glacial lakes increased in this basin. There were 71 glacial lakes in the Nidu Zangbo Basin with a total area of 3.42 km2 in 2016, among which 14 lakes, accounting for an area>0.05 km2, were considered to be potentially dangerous glacial lakes (PDGLs) in this study. At the end of 2017, the proposed approach identified 6 of 14 PDGLs as high potentially hazardous, among which Jinwucuo, with the highest hazardous score, occurred GLOF event on June 26, 2020, which proves the robustness of the approach. Thus, the GOLF susceptibility in the Nidu Zangbo Basin was suggested to be evaluated regularly with the approach and update monitoring data and remote sensing images. The study provides valuable clues to assess the GLOF susceptibilities in High Mountain Asia (HMA).

Climate change and glacial lake outburst flood (GLOF) risk perceptions: An empirical study of Ghizer District, Gilgit-Baltistan Pakistan

Risk perception is gaining attention in disaster risk reduction and climate change-related studies. It plays a role in shaping the preparedness, adaptation, response, and resilience of vulnerable communities. However, the literature suggests that risk perception is contextually sensitive. There are limited studies that offer insights on the risk perception of climate change and related disaster events in an integrated manner. This study investigates the climate change and associated glacial lake outburst floods risk perceptions of the remotely located vulnerable communities in the northern mountainous region of Gilgit Baltistan, Pakistan. The study employed the quantitative method of household surveys in vulnerable communities for data collection. An extensive literature review was conducted to select the key indicators to determine the risk perception in the selected communities. Indexing and multiple regression analyses were performed to draw the results of the study. GLOF risk perception has been found higher as compared to the climate change risk perception. Fear has been found as the most significant determinant of the GLOF risk perception, whereas socio-economic variables of gender, education, duration of living, and past hazard experiences have been found to be predictors of climate change risk perception. Also, most people did not believe in a link between climate change and GLOF events. The study also provides an important finding for an effective policy formulation that communities are aware of the life-threatening impacts of GLOFs, which may be used to increase community resilience against GLOFs through risk communication, preparedness campaigns, and climate change adaptation measures.

Temporal and Spatial Changes and GLOF Susceptibility Assessment of Glacial Lakes in Nepal from 2000 to 2020

Glacial lakes are a sensitive indicator of regional climate change and one of the initiators of glacier disasters. It is of great significance to understand the spatial distribution and change characteristics of glacial lakes for exploring their response patterns to climate change and assessing the glacial lake outburst flood (GLOF) susceptibility. Based on Gaofen-1/6 PMS, Sentinel-2A/2B MSI and Landsat TM/ETM+/OLI images from 2000 to 2020, we integrated geographic information technology and mathematical and statistical methods to analyze the spatial and temporal distribution of glacial lakes in Nepal and their dynamic changes, and further discriminated and evaluated the GLOF susceptibility of glacial lakes. The results show that there were 2420 glacial lakes in Nepal in 2020, mainly distributed within the 4500~5500 m, with an area of 87.21 km2 and a water storage of 1921.72 × 106 m3. The number and area of glacial lakes with each area above 0.01 km2 in Nepal showed an increasing trend from 2000 to 2020, while 499 new glacial lakes were born, 139 lakes disappeared, the area and water storage increased by 19.46 km2, 403.07 × 106 m3, respectively. Glacial lakes at altitudes <3000 m were relatively stable, while the number and area of glacial lakes at altitudes within 4500~5500 m increased rapidly. We assessed the GLOF susceptibility of 40 moraine-dammed glacial lakes with an area above 0.2 km2 in Nepal, and found that there were 8, 12, 14 and 6 glacial lakes with low, medium, high and very high susceptibility, respectively. Among glacial lakes with very high GLOF susceptibility, potential GLOF events of Tsho Rolpa glacial lake, Lower Barun glacial lake and glacial lake with code of GL87091E27797N will cause great harm to downstream regions. GLOFs in Nepal will be in an active status in the future, therefore, the dynamics of glacial lakes and their surroundings should be continuously monitored.

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

Abstract. Glacial lake outburst floods (GLOFs) are among the most concerning consequences of retreating glaciers in mountain ranges worldwide. GLOFs have attracted significant attention amongst scientists and practitioners in the past 2 decades, with particular interest in the physical drivers and mechanisms of GLOF hazard and in socioeconomic and other human-related developments that affect vulnerabilities to GLOF events. This increased research focus on GLOFs is reflected in the gradually increasing number of papers published annually. This study offers an overview of recent GLOF research by analysing 594 peer-reviewed GLOF studies published between 2017 and 2021 (Web of Science and Scopus databases), reviewing the content and geographical focus as well as other characteristics of GLOF studies. This review is complemented with perspectives from the first GLOF conference (7–9 July 2021, online) where a global GLOF research community of major mountain regions gathered to discuss the current state of the art of integrated GLOF research. Therefore, representatives from 17 countries identified and elaborated trends and challenges and proposed possible ways forward to navigate future GLOF research, in four thematic areas: (i) understanding GLOFs – timing and processes; (ii) modelling GLOFs and GLOF process chains; (iii) GLOF risk management, prevention and warning; and (iv) human dimensions of GLOFs and GLOF attribution to climate change.

Transition of a small Himalayan glacier lake outburst flood to a giant transborder flood and debris flow

Glacial lake outburst floods (GLOFs) are a great concern for the Himalaya, as they can severely damage downstream populations and infrastructures. These floods originate at high altitudes and can flow down with enormous energy and change the terrain’s existing morphology. One such devastating event occurred on the night of 5 July 2016, from the inconspicuous Gongbatongsha Lake, located in the Poiqu basin, Eastern Himalaya. The Poiqu basin in the Tibetan Autonomous Region currently contains numerous big glacial lakes; however, this event originated from a small lake. The GLOF was triggered following heavy precipitation that led to a slope failure above the lake and deposition of debris into the lake, which breached the moraine dam and rapidly drained the entire lake. The flood damaged several downstream infrastructures, including the Arniko highway, the Upper Bhotekoshi hydropower plant, and several buildings as it made its way into the Bhotekoshi basin in Nepal. This study adopts a multi-model approach to reconstruct the GLOF trigger and the flood’s transformation into a severe debris flow. Proxies including flow discharge, flow velocity, runout distances were used to calibrate the model and validate the results. Results reveal that a debris flow of volume ranging between 3000 and 6000 m3 from the headwall must have led to lake overfill, eventually leading to the GLOF event. The GLOF showed a significant increase in peak discharge from 618 to 4123 m3 s−1 at the Zhangzangbo-Bhotekoshi confluence. The average velocity of the flow is calculated to be ~ 5.5 m s−1. Reconstruction of the erosion and deposition dynamics show that maximum erosion occurred in the first 6.5 km, with maximum deposition occurring near the Upper Bhotekoshi hydropower station. The modeling indicates that the availability of the entrainable debris along the channel, likely from the previous landslides, amplified the event by three orders of magnitude-additional water ingested from the river. Overall, we demonstrate how the small-scale Gongbatongsha GLOF amplified downstream by incorporating pre-existing sediment in the valley and triggered damaging secondary landslides leading to an economic loss of > 70 million USD.

Hydrological investigation of subsurface Glacial Lake Outburst Floods at Bindo Gol Valley under changing climate, Pakistan

Climate contributed temperature and precipitation has triggered several glaciological hazards in mountainous regions of Pakistan. The present study identifies glacial architecture of Bindo Gol valley (BGV) glacier present in HinduKush region of Pakistan with emphasis on Glacial Lake Outburst Floods (GLOF) lake development. The study integrates meteorological (temperature, precipitation) and geophysical (Ground Penetrating Radar (GPR)) data to demarcate glacial architecture and possibility of GLOF lake development. Several moraines filled crevasses were identified (from GPR) mostly towards the center and south of the study area. Some of these crevasses were connected to the surficial running water channels that were also detected by GPR. A dense network of cavities was identified towards southeast of the glacier, despite being shallow, these cavities could facilitate the development of GLOF lake. The study indicates a good relationship between geophysical (presence of crevasses and subsurface cavities) and meteorological (variations in temperature and precipitation) data for the identification of source for the accumulation of larger volumes of water possibly resulting in GLOF events.