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On the night of October 3, 2023, the moraine-dammed South Lhonak Lake in Sikkim suddenly discharged a substantial volume of water, resulting in a glacial lake outburst flood (GLOF) that caused 178 fatalities and the destruction of three downstream hydropower projects, making it one of the most devastating GLOF events in the Himalayas. Leveraging satellite imagery and numerical modeling, this study analyzed the long-term evolution and outburst mechanisms of South Lhonak Lake, as well as the propagation of the GLOF, to provide valuable insight for regional GLOF risk assessment and management. The South Lhonak GLOF was triggered by the collapse of a massive lateral moraine, with an estimated collapse material volume of 16.75 × 106 m3. Following the outburst flood, the lake area decreased by 15.38%, from 1.69 ± 0.03 to 1.46 ± 0.03 km2. The impact of the GLOF extended to 169 km downstream, corresponding to a total inundation area of 32.04 ± 1.91 km2. A multi-phase r.avaflow model was employed to simulate the mass flow and cascading process. An impulse wave displacement speed of approximately 26 m·s−1 was observed after the collapse of the lateral moraine, and the overtopping height on the moraine dam reached 16.11 m. The hydrograph at the dam breach site revealed that approximately 38.49 × 106 m3 of water was released during the drainage process and that the peak discharge of 3.02 × 105 m3·s−1 occurred 140 s after the dam breach. Upon entering the downstream channel, the peak discharge was attenuated, and its duration was prolonged because of the influence of the valley terrain. Given the current challenges in accurately identifying potential avalanche zones, we identified a discrepancy between GLOF triggers and modeling scenarios. A novel framework for GLOF hazard assessment involves driving collapses of varying magnitudes to strike the lake and subsequently simulating GLOF initiation and downstream propagation for the most plausible outburst scenario. This conceptual approach can be used to design artificial drainage and determine dam immobilization engineering criteria and to evaluate the resistance performance of remedial measures under specific striking probabilities. [ABSTRACT FROM AUTHOR]

Climate change leads to changes in glacier mass balance, including steady advancements and surges that reposition the glacier snouts. Glacier advancement can dam proglacial meltwater lakes. Within the Karakoram and surrounding regions, the positive feedback of climate change has resulted in more frequent ice-dammed glacial lake outburst floods (GLOFs), often facilitated by englacial conduits. However, the complex and multi-factor processes of conduit development are difficult to measure. Determining the lake depths that might trigger GLOFs and the numerical model specifications for breaching is challenging. Empirical estimates of lake volumes, along with field-based monitoring of lake levels and depths and the assessment of GLOF hazards, enable warnings and damage mitigation. Using historical data, remote sensing techniques, high-resolution imagery, cross-correlation feature tracking, and field-based data, we identified the processes of lake formation, drainage timing, and triggering depth. We developed empirical approaches to determine lake volume and trigger water pressure leading to a GLOF. A correlation, albeit a weak one, between glacier surge velocity and lake volume reveals that glacier surge may play a crucial role in lake formation and thus controls the size and volume of the lake. Lake volume estimation involves geometric considerations of the lake basin shape. A GLOF becomes likely when the lake's normalized depth (n′) exceeds 0.60, equivalent to a typical water pressure on the dam face of 510 kPa. These field and remotely sensed findings not only offer valuable insights for early warning procedures in the Karakoram but also suggest that similar approaches might be effectively applied to other mountain environments worldwide where GLOFs pose a hazard. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The Shishapangma region, situated in the middle of the Himalayas, is rich in glacial lakes and glaciers. Hence, glacial lake outburst floods (GLOFs) have become a top priority because of the severe threat posed by GLOFs to the downstream settlements. This study presents a comprehensive analysis of GLOF hazards using multi-source remote sensing datasets and designs a flood model considering the different breaching depths and release volumes for the Galong Co region. Based on high-resolution optical images, we derived the expanding lake area and volume of glacial lakes. We monitored deformation velocity and long-term deformation time series around the lake dam with Small BAseline Subset Interferometric Synthetic Aperture Radar (SBAS-InSAR). The glacier thinning trend was obtained from the difference in the Digital Elevation Model (DEM). We identified potential avalanche sources by combining topographic slope and measurable deformation. We then carried out flood modeling under three different scenarios using the hydrodynamic model HEC-RAS for Galong Co, which is formed upstream of Nyalam. The results show that the Nyalam region is exposed to high-intensity GLOFs in all scenarios. The larger breaching depth and release volumes caused a greater flow depth and peak discharge. Overall, the multiple remote sensing approaches can be applied to other glacial lakes, and the modeling can be used as a basis for GLOF mitigation. [ABSTRACT FROM AUTHOR]

Gya river, one of the main tributary of Indus, hosts several scattered palaeoflood deposits. The chronology, genesis and spatiotemporal relationships of these scattered deposits can throw light to the regional and global climatic fluctuations and their implications for the evolution of the valley. The valley structure of the Gya river consists of a broad middle reach alternating with narrow valleys and gorges in the upper and lower reaches which can be blocked by the slightest of sediment discharge damming the entire valley. The geomorphological, sedimentological and chronological study in this valley reveals multiple short-lived lake phases at 21–19.9 ka, 13 ka and 4.5 ka in the broader reach of the river during the transition periods when climate rapidly fluctuates between cold-dry and warm-wet. The damming in the valley is the result of the glacial lake outbursts in the head waters of the Gya catchment blocking the narrow lower reaches of the main channel by massive sediment. These lakes that are formed by valley damming contains ~108 m3 of water which subsequently breach out causing significant geomorphic changes on reach scale along the Gya river channel. [ABSTRACT FROM AUTHOR]

Glacial lake outburst floods (GLOFs) pose an increasing hazard to communities living downstream of glaciated areas of the Northern Patagonia Icefield (NPI). The proliferation of GLOF events poses a growing hazard to human development and infrastructure which is rapidly expanding into formerly isolated areas. The outlet glaciers on the eastern flank of the NPI, in particular, have experienced an increase in the frequency of GLOFs, threatening downstream communities with the potential for future events. Using a satellite-derived DEM and UAV imagery, we evaluated flood parameters of a 16 March 1989 GLOF event in the Valle Soler. Calculated flood volume was in excess of 140 × 106 m3 while the peak discharge was approximately 20,000 m3/s. This newly calculated flood discharge value distinguishes this event as the largest recorded glacial moraine outburst flood in the literature and is significantly larger than previous estimates (1,800–2,000 m3/s) for this incident. [ABSTRACT FROM AUTHOR]

This study discusses the timing and maximum flood level of the Nedre Glomsjø outburst flood, Norway, based on sediment records retrieved from 15 bog and lake basins located close to the purported maximum flooded level. The sediment records in 12 of the basins consist of a distinct light‐coloured silty bed that is correlated to the outburst‐flood‐deposited 'Romerike Silt Bed' identified elsewhere in the region. The silt bed is recorded in basins up to a certain elevation and is absent above this level. The new maximum flood level inferred from the basin sediment records exceeds the established landform‐induced palaeostage indicators by 5–10 m. The data indicate a higher maximum flood level and larger inundation area than previously suggested and highlight the importance of acquiring a wide range of geological data when reconstructing palaeofloods. Radiocarbon dates of terrestrial macrofossils found stratigraphically above and below the Romerike Silt Bed suggest that the glacial lake Nedre Glomsjø outburst flood occurred between 10.5 and 10.3 cal. ka BP. The new and well‐constrained timing of the outburst flood is beneficial for reconstructing regional deglaciation and provides a precise age for the Romerike Silt Bed chronostratigraphical marker, which is of value for studies in SE Norway and adjacent regions. [ABSTRACT FROM AUTHOR]

The Sikkim region of the Eastern Himalayas is highly susceptible to Glacial Lake Outburst Floods (GLOFs), a risk that has increased significantly due to rapid glacial retreat driven by climate change in recent years. This study presents a comprehensive evaluation of GLOF susceptibility in Sikkim, employing Analytic Hierarchy Process (AHP) and Fuzzy Analytic Hierarchy Process (FAHP) models. Key factors influencing GLOF vulnerability, including lake volume, seismic activity, precipitation, slope, and proximity to rivers, were quantified to develop AHP and FAHP based susceptibility maps. These maps were validated using Receiver Operating Characteristic (ROC) curves, with the AHP method achieving an Area Under the Curve (AUC) of 0.92 and the FAHP method scoring 0.88, indicating high predictive accuracy for both models. A comparison of the two approaches revealed distinct characteristics, with FAHP providing more granular insights into moderate-risk zones, while AHP offered stronger predictive capability for high-risk areas. Our results indicated that the expansion of glacial lakes, particularly over the past three decades, has heightened the potential for GLOFs, highlighting the urgent need for continuous monitoring and adaptive risk mitigation strategies in the region. This study, in addition to enhancing our understanding of GLOF risks in Sikkim, also provides a robust framework for assessing and managing these risks in other glacial regions worldwide. [ABSTRACT FROM AUTHOR]

Establishing an effective real-time monitoring and early warning system for glacier lake outburst floods (GLOFs) requires a full understanding of their occurrence mechanism. However, the harsh conditions and hard-to-reach locations of these glacial lakes limit detailed fieldwork, making satellite imagery a critical tool for monitoring. Lake Mercbacher, an ice-dammed lake in the central Tian Shan mountain range, poses a significant threat downstream due to its relatively high frequency of outbursts. In this study, we first monitored the daily changes in the lake area before the 2022 Lake Mercbacher outburst. Additionally, based on historical satellite images from 2014 to 2021, we calculated the maximum lake area (MLA) and its changes before the outburst. Furthermore, we extracted the proportion of floating ice and water area during the period. The results show that the lake area of Lake Mercbacher would first increase at a relatively low speed (0.01 km2/day) for about one month, followed by a relatively high-speed increase (0.04 km2/day) until reaching the maximum, which would last for about twenty days. Then, the lake area would decrease slowly until the outburst, which would last five days and is significant for early warning. Moreover, the floating ice and water proportion provides more information about the outburst signals. In 2022, we found that the floating ice area increased rapidly during the early warning stage, especially one day before the outburst, accounting for about 50% of the total lake area. Historical evidence indicates that the MLA shows a decreasing trend, and combining it with the outburst date and climate data, we found that the outburst date shows an obvious advance trend (6 days per decade) since 1902, caused by climate warming. Earlier melting results in an earlier outburst. This study provides essential references for monitoring Lake Mercbacher GLOFs and building an effective early warning system. [ABSTRACT FROM AUTHOR]

We describe and model the evolution of a recent landslide, tsunami, outburst flood, and sediment plume in the southern Coast Mountains, British Columbia, Canada. On November 28, 2020, about 18 million m3 of rock descended 1,000 m from a steep valley wall and traveled across the toe of a glacier before entering a 0.6 km2 glacier lake and producing >100‐m high run‐up. Water overtopped the lake outlet and scoured a 10‐km long channel before depositing debris on a 2‐km2 fan below the lake outlet. Floodwater, organic debris, and fine sediment entered a fjord where it produced a 60+km long sediment plume and altered turbidity, water temperature, and water chemistry for weeks. The outburst flood destroyed forest and salmon spawning habitat. Physically based models of the landslide, tsunami, and flood provide real‐time simulations of the event and can improve understanding of similar hazard cascades and the risk they pose. Plain Language Summary: Glacier retreat exposes unstable slopes that can suddenly fail. We describe and model one such event with far‐reaching consequences. The landslide mass (50 million tonnes, equivalent to the combined mass of all Canadian automobiles) entered and suddenly drained a 0.6‐km2 alpine lake in the southern Coast Mountains of British Columbia. Displaced water destroyed salmon‐spawning habitat over a distance of 8.5 km and created a plume of sediment and organic matter more than 60 km from the head of the fjord into which the floodwaters discharged. Physically based models are able to simulate the hazard cascade, and such models could be used to improve hazard and risk assessments of these events under future climate change. Key Points: Rapid glacier retreat created conditions that allowed a geohazard cascade to occur in a steep mountain valleyWe describe and model a recent landslide, tsunami, and outburst flood that typifies a deglacial geohazard cascadeFuture work should predict new glacial lakes and use physically based models to simulate the slope, tsunami, and outburst flood hazards [ABSTRACT FROM AUTHOR]

The melting of glaciers has led to an unprecedented increase in the number and size of glacial lakes, particularly in the Himalayan region. A glacial lake outburst flood (GLOF) is a natural hazard in which water from a glacial or glacier-fed lake is swiftly discharged. GLOFs can significantly harm life, infrastructure, and settlements located downstream and can have considerable ecological, economic, and social impacts. Based on a dam breach model, BREACH, and a hydrodynamic model, HEC-RAS (Hydrologic Engineering Centre's River Analysis System), we examined the potential consequences of a GLOF originating from the Thorthomi glacial lake, located within the Phochhu river basin, one of Bhutan's largest and rapidly expanding glacial lakes. Our analysis revealed that following a breach the Thorthomi glacial lake will likely discharge a peak flow of 16 360 m3s-1 within 4 h. Such a discharge could potentially cause considerable damage, with an estimated 245 ha of agricultural land and over 1277 buildings at risk of inundation. To mitigate ecological, economic, and social impacts on downstream areas, our results emphasise an urgent need for understanding and preparing for the potential consequences of a GLOF from Thorthomi lake. Our findings provide valuable insights for policymakers and stakeholders involved in disaster management and preparedness. [ABSTRACT FROM AUTHOR]

Glacial lake outburst floods (GLOFs) are sudden, and often hazardous, floods occurring upon the failure of a glacial lake dam or moraine. A GLOF occurred at Sulzenau Lake (Tyrol, Austria) in August 2017 due to a partial moraine and dam failure, damaging nearby infrastructure. Due to the ongoing retreat of Sulzenau Glacier, the areal extent, depth, water volume, and shoreline configuration of Sulzenau Lake fluctuate over both short‐ and long‐term periods. Here, we used remote sensing data to create a detailed geomorphological overview of the valley, analyse the lake's evolution since 2009, and characterize the conditions leading to the 2017 dam failure. Using optical remote sensing imagery, we generated detailed pre‐ and post‐event geomorphological maps of Sulzenau Lake and areas impacted by the GLOF to characterize erosional and depositional zones. We employed the Normalized Difference Water Index (NDWI) and mapped the post‐event boulder distribution. Based on multi‐temporal mapping, we calculated water volumes, analysed changes in lake and glacier surfaces since 1970, and compared them with ERA‐5 meteorological data. Lake growth was primarily due to rising temperatures and glacier retreat. In 2017, both precipitation and air temperatures in the Sulzenau Valley exceeded the 1991–2021 averages, with precipitation 14.8% higher and air temperatures 0.35°C above the 30‐year mean. Ice velocities for Sulzenau Glacier reached 170 m/year during 2015–2022. By modelling flow conditions required for observed boulder movements during the GLOF, we constrained the peak discharge to 150–200 m3/s. No significant pre‐2017 GLOF activity or meteorological anomalies were detected. Accordingly, we attribute the GLOF and dam failure to an increased meltwater flux and increased precipitation, possibly augmented by subglacial/englacial lake drainage. The 2017 Sulzenau Valley GLOF is a pertinent example of environmental changes and associated hazards in high‐mountain glacial environments due to global warming. [ABSTRACT FROM AUTHOR]

The Chhombo Chhu Watershed of Tista basin in Sikkim Himalaya, located between the Greater Himalayan range and the Tethyan Sedimentary Sequence, is the storehouse of number of glacial lakes with large areas and volumes. In this study, we mapped the glacial lakes changes between 1975–2018 and assessed its dynamics based on manual analysis of optical satellite images using KeyHole-9 Hexagon (∼4 m), Landsat Series (∼15–30 m), and Sentinel 2 A-MSI (∼10–20 m) imagery and verified during field surveys. The results show that the number of lakes has increased from 62 to 98, and its total area expanded significantly by ∼34.6 ± 5.4%, i.e. from 8.5 ± 0.2 km² in 1975 to 11.4 ± 0.6 km² by 2018, at an expansion rate of 0.8 ± 0.1% a−1. Lake outburst susceptibility result reveals that a total of twenty-seven potentially dangerous glacial lakes exist in the watershed; 5 have a status of ‘high’ outburst probability, 17 ‘medium’ and 5 ‘low’. The majority of the proglacial lakes in the watershed have significantly enlarged due to the faster melting and calving processes as a result of accelerating increasing long-term average annual trend of temperature (+0.283° Ca−1; 95% confidence level) and homogeneous or slightly declining precipitation. HIGHLIGHTS We present a contemporary watershed-based comprehensive glacial lake inventory and its’ inter-periodic changes in Sikkim Himalaya. We estimate the first-order lake volumes in the glacier bearing watershed of Chhombo chhu. We provide two lake classification approaches to observe change characteristics for the 1975–2018 period. We compare and analyse the climate-driven factors responsible for lake expansion. We have recorded and analysed twenty-seven potentially dangerous glacial lakes evaluating probability of lake outbursts. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Global warming has accelerated alpine glacier melting and led to an increased risk of glacial lake outburst floods (GLOFs). This paper extracted glacial lake boundaries in the Tienshan Mountains of Central Asia from 1990 to 2023, analyzed their spatiotemporal variations and evaluated their risk levels under current and future scenarios. The results show that glacial lakes are predominantly distributed in the Central and Western Tienshan, accounting for 75% of the total number in the Tienshan region. The number and area of glacial lakes increased by 148% (from 1837 to 4557) and 71.83% (from 119.73 to 205.73 km2) during 1990 to 2023, with moraine lake expansion predominating. In the Western Tienshan, the high or very high risk of GLOF is 3–4 times that of other areas. By the middle of the twenty-first century, GLOF risk will continue to increase, especially in the Western Tienshan. This study can provide scientific foundation for disaster mitigation in the downstream areas. [ABSTRACT FROM AUTHOR]

The article focuses on the increasing incidence of Glacial Lake Outburst Floods (GLOFs) in the Indian Himalayan region due to climate change and terrain conditions. It discusses the vulnerability of proglacial lakes formed by glacier retreat, citing examples such as the recent South Lhonak lake GLOF in Sikkim. It emphasizes the environmental and societal impacts of these floods.

The polar regions experience widespread transformations, such that efficient methods are needed to monitor and understand Arctic landscape changes in response to climate warming and low-frequency, high-magnitude hydrological and geomorphological events. One example of such events, capable of causing serious landscape changes, is glacier lake outburst floods. On 6 August 2017, a flood event related to glacial lake outburst affected the Zackenberg River (NE Greenland). Here, we provided a very-high-resolution dataset representing unique time series of data captured immediately before (5 August 2017), during (6 August 2017), and after (8 August 2017) the flood. Our dataset covers a 2.1 km long distal section of the Zackenberg River. The available files comprise (1) unprocessed images captured using an unmanned aerial vehicle (UAV; 10.5281/zenodo.4495282, Tomczyk and Ewertowski, 2021a) and (2) results of structure-from-motion (SfM) processing (orthomosaics, digital elevation models, and hillshade models in a raster format), uncertainty assessments (precision maps), and effects of geomorphological mapping in vector formats (10.5281/zenodo.4498296, Tomczyk and Ewertowski, 2021b). Potential applications of the presented dataset include (1) assessment and quantification of landscape changes as an immediate result of a glacier lake outburst flood; (2) long-term monitoring of high-Arctic river valley development (in conjunction with other datasets); (3) establishing a baseline for quantification of geomorphological impacts of future glacier lake outburst floods; (4) assessment of geohazards related to bank erosion and debris flow development (hazards for research station infrastructure – station buildings and bridge); (5) monitoring of permafrost degradation; and (6) modelling flood impacts on river ecosystem, transport capacity, and channel stability. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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.

Existence and expansion of glacial lakes from Sikkim Himalaya enhances the susceptibility of the region to glacial lake outburst floods (GLOF) causing destruction of infrastructures and loss of life in the downstream region. Apart from the expanding glacial lake, various topographic factors play important role in its susceptibility to GLOF. This study aims to find out the GLOF susceptibility of a relatively stable lake, Shako Cho in terms of areal expansion using different topographic parameters. The lake volume has been estimated using area-based scaling method. Using Sentinel-2A satellite imagery and ALOS- PALSAR digital elevation model, probable avalanche pathway, steep lakefront area (SLA) have been mapped. Estimating the potential lake lowering height from the digital elevation model, potential flood volume (PFV) has been quantified. A band-ratio method has been employed to extract the debris-cover around the glacial lake. This lake has a PFV of 45.478*106 m3 water. Sikkim being a hilly terrain, some of its glacial lakes are located in highly avalanche prone zone. Excessive snowfall often causes snow avalanche in those region. Thus a snow-avalanche triggered GLOF simulation in HEC-RAS 5.0.6, using 2D dam breach scenario has been performed to evaluate its impact on the downstream region. [ABSTRACT FROM AUTHOR]

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 km 2 (+ 56 %) to 0.56 km 2 and subsequently decreased to 0.26 km 2 (- 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 cubic meters, an average breach time of 0.62 h, and an average peak discharge of 5602 m 3 /s at the dam. Based on pre- and post-event high-resolution satellite scenes, we identified a large debris landslide originating from western lateral moraine that was most likely triggered by extremely heavy, south-Asian-monsoon-associated rainfall in June 2020. 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), as well as retrogressive erosion without a major impact wave (Scenario B). Both scenarios 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. Comparison of the simulation results with field evidence points towards Scenario B, with a peak discharge of 4600 m 3 /s. 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 can be plausibly linked 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. [ABSTRACT FROM AUTHOR]

The 16th of June 1818, the failure of the Giétro glacier in the Swiss Alps provoked an outburst flood that devastated the Bagnes valley, causing 34 deaths and major damages to buildings, road system, hydraulic infrastructures and crops. This disaster had a major impact on the economy of the valley and created a great movement of solidarity. It remains today a well-known historical natural disaster. In order to reconstruct the course of the wave and to map the flood, we used an interdisciplinary approach by crossing historical and geomorphological data. We first compiled and mapped the large number of historical data available in the local and state archives. These data were then completed by geomorphological observations made on the field and on numerical documents. The resulting map presents the spatial extent of the flood and water depths. This article shows the validity of interdisciplinary approaches for reconstructing past natural disasters. [ABSTRACT FROM AUTHOR]

Glacial lakes represent a threat for the populations of the Andes and numerous disastrous glacial lake outburst floods (GLOFs) occurred as a result of sudden dam failures or dam overtoppings triggered by landslides such as rock/ice avalanches into the lake. This paper investigates a landslide-triggered GLOF process chain that occurred on February 23, 2020, in the Cordillera Vilcabamba in the Peruvian Andes. An initial slide at the SW slope of Nevado Salkantay evolved into a rock/ice avalanche. The frontal part of this avalanche impacted the moraine-dammed Lake Salkantaycocha, triggering a displacement wave which overtopped and surficially eroded the dam. Dam overtopping resulted in a far-reaching GLOF causing fatalities and people missing in the valley downstream. We analyze the situations before and after the event as well as the dynamics of the upper portion of the GLOF process chain, based on field investigations, remotely sensed data, meteorological data and a computer simulation with a two-phase flow model. Comparison of pre- and post-event field photographs helped us to estimate the initial landslide volume of 1–2 million m3. Meteorological data suggest rainfall and/or melting/thawing processes as possible causes of the landslide. The simulation reveals that the landslide into the lake created a displacement wave of 27 m height. The GLOF peak discharge at the dam reached almost 10,000 m3/s. However, due to the high freeboard, less than 10% of the lake volume drained, and the lake level increased by 10–15 m, since the volume of landslide material deposited in the lake (roughly 1.3 million m3) was much larger than the volume of released water (57,000 m3, according to the simulation). The model results show a good fit with the observations, including the travel time to the uppermost village. The findings of this study serve as a contribution to the understanding of landslide-triggered GLOFs in changing high-mountain regions. [ABSTRACT FROM AUTHOR]

Glacial lake outburst floods (GLOFs) are a severe threat to communities in the Himalayas; however, GLOF mitigation strategies have been implemented for only a few lakes, and future changes in hazard are rarely considered. Here, we present a comprehensive assessment of current and future GLOF hazard for Gepang Gath Lake, Western Himalaya, considering rock and/or ice avalanches cascading into the lake. We consider ground surface temperature and topography to define avalanche source zones located in areas of potentially degrading permafrost. GLOF process chains in current and future scenarios, also considering engineered lake lowering of 10 and 30 m, were evaluated. Here, varied avalanche impact waves, erosion patterns, debris flow hydraulics, and GLOF impacts at Sissu village, under 18 different scenarios were assessed. Authors demonstrated that a larger future lake does not necessarily produce larger GLOF events in Sissu, depending, among other factors, on the location from where the triggering avalanche initiates and strikes the lake. For the largest scenarios, 10 m of lowering reduces the high‐intensity zone by 54% and 63% for the current and future scenarios, respectively, but has little effect on the medium‐intensity flood zone. Even with 30 m of lake lowering, the Sissu helipad falls in the high‐intensity zone under all moderate‐to‐large scenarios, with severe implications for evacuations and other emergency response actions. The approach can be extended to other glacial lakes to demonstrate the efficiency of lake lowering as an option for GLOF mitigation and enable a robust GLOF hazard and risk assessment. Plain Language Summary: Glacial lake outburst floods (GLOFs) have the potential to cause severe damage to the downstream regions. GLOFs can be triggered by a host of geomorphic, climatic, and seismic factors, one of which can be mass wasting such as avalanches entering a lake, particularly in the Himalaya where surrounding slopes are steep and destabilizing. In the Western Himalaya, Gepang Gath Lake has grown over the years to become the largest lake in Himachal Pradesh. The lake has potential to grow more than double its size in the future. The existence of warming permafrost (frozen ground) in the surrounding steep slopes of the lake makes it susceptible to failure. Assessment of GLOF process chains including avalanche impact on the lake, frontal dam breaching, and downstream impact shows that the nearest settlement at Sissu is exposed to present and future GLOFs. We further evaluated mitigation options, including lake level lowering by 10 and 30 m, to evaluate the changes in the GLOF intensities downstream of the lake. It is seen that there is a significant reduction in the GLOF impact downstream when the lake levels are lowered, but the risk from very large events is not eliminated. Key Points: Sissu is potentially exposed to high‐intensity glacial lake outburst flood hazard under all current scenarios and the moderate and large magnitude future scenariosLake lowering by 10 m reduces the high‐intensity zone by 54% and 63% for the current and future scenarios respectivelyLake lowering by 30 m leads to a reduction in the affected area of 78% and 93% in current and future scenarios, respectively [ABSTRACT FROM AUTHOR]

The study analyzed synthetically spatiotemporal distribution and evolution status of moraine-dammed lakes and potential dangerous glacial lakes (PDGLs) in the Qinghai–Tibetan Plateau (QTP) and revealed integrated risk degree of county-based glacier lake outburst floods (GLOFs) disaster by combining hazard of PDGLs, regional exposure, vulnerability of exposed elements, and adaptability and using the analytic hierarchy process and weighted comprehensive method. The results show there are 654 moraine-dammed lakes (> 0.018 km2) with a total area of 200.25 km2 in the QTP in the 2010s, of which 246 lakes with a total area of 78.38 km2 are identified as PDGLs. Compared with 1990s, the number of lakes decreased only by 2.22%, whereas total lake area expanded by 25%. All PDGLs area increased by 84.40% and was higher significantly than 4.06% of non-PDGLs. The zones at very high and high integrated risk of GLOF disasters are concentrated on the middle Himalayas, middle-eastern Nyainqentanglha, and southern Tanggula Mountain. On the county scale, Nyalam, Tingri, Dinggyê, Lhozhag, Zhongba, Gamba, Kangma of the Himalayas, and Nierong, Dingqing, Banbar, Baqing, Bomi, and Basu of the Nyainqentanglha are located in the very high-risk zone, whereas other areas have low and very low integrated risk. The regionalization results for GLOF disasters risk are consistent with the distribution of historical GLOF disaster sites. [ABSTRACT FROM AUTHOR]

Two detailed geomorphological maps (1:2000) depicting landscape changes as a result of a glacial lake outburst flood were produced for the 2.1-km-long section of the Zackenberg river, NE Greenland. The maps document the riverscape before the flood (5 August 2017) and immediately after the flood (8 August 2017), illustrating changes to the riverbanks and morphology of the channel. A series of additional maps (1:800) represent case studies of different types of riverbank responses, emphasising the importance of the lateral thermo-erosion and bank collapsing as significant immediate effects of the flood. The average channel width increased from 40.75 m pre-flood to 44.59 m post-flood, whereas the length of active riverbanks decreased from 1729 to 1657 m. The new deposits related to 2017 flood covered 93,702 m2. The developed maps demonstrated the applicability of small Unmanned Aerial Vehicles (UAVs) for investigating the direct effects of floods, even in the harsh Arctic environment. [ABSTRACT FROM AUTHOR]

Flash flood after the breaching of South Lhonak Lake (glacier lake outburst flood (GLOF)) along with prolonged rainfall event in the first week of October 2023 significantly triggered numerous landslides along the side of the river, roads, and vulnerable slopes within the upper catchment of Teesta basin, Sikkim. In this paper, we present documentation on the occurrences of series of landslides just after the flood and heavy rainfall event in upper Teesta basin and try to find out the relevant causes. Primarily, flash flood due to glacial lake outburst and extensive rainfall accelerated series of landslides; however, the landslides are controlled by some other secondary factors including soil and slope condition, lithological diversity, geological discontinuities, and anthropogenic influences. The InSAR coherence analysis significantly shows the lowering of coherence value (decorrelation) in the moraine dam area within pre and post GLOF event which indicates breaching of the dam. The result of the slope stability assessment showed that majority slopes along the river Teesta are highly vulnerable with less safety factor and low cohesiveness of soil materials. Furthermore, the northern part of the MCT (Main Central Thrust) is composed by high-grade metamorphic rocks with exposed structures (high lineament density) that provoke landslides. Consequently, the result also highlighted that most of the slides along the side of Teesta occurred due to high water discharge and elevated gauge height after the GLOF event. Here, NH-10 (National Highway 10) runs on the high grade vulnerable litho-units and in between Dikchu and Chungthang, NH-10 is passing at the close proximity of river Teesta. So, different pockets of North Sikkim along the NH-10 were engulfed by high river discharge and gauge height due to large scale destruction of Chungthang Hydroelectric Power Plant constructed across the river Teesta. [ABSTRACT FROM AUTHOR]

The melting of glaciers has led to an unprecedented increase in the number and size of glacial lakes, particularly in the Himalayan region. A Glacial Lake Outburst Flood (GLOF) is a natural hazard in which water from a glacial or glacier-fed lake is swiftly discharged. GLOFs can significantly harm life, infrastructure, and settlements located downstream, and can cause considerable ecological, economic, and social impacts. Based on a dam breach model, BREACH, and a hydrodynamic model, HEC-RAS, we examined the potential consequences of a GLOF originating from the Thorthomi glacial lake, located within the Phochhu River Basin, one of Bhutan's largest and rapidly expanding glacial lakes. Our analysis revealed that, following a breach, the Thorthomi glacial lake will likely generate a peak flow of 16,360 m³ s-1 within four hours. Such discharge could potentially cause considerable damage, with an estimated 245 hectares of agricultural land and over 1,277 buildings at risk for inundation. Our results emphasize an urgent need for understanding and preparing for the potential consequences of a GLOF from Thorthomi Lake in order to mitigate ecological, economic, and social impacts on downstream areas. Our findings provide valuable insights for policymakers and stakeholders involved in disaster management and preparedness. [ABSTRACT FROM AUTHOR]

Highlights • Dalung and Padam glaciers and their associated lakes have been studied using multi-temporal datasets of Landsat (MSS, TM, ETM+), Indian Remote Sensing LISS-III, Google EarthTM, ASTER GDEM and Survey of India topographic maps. • The Dalung Glacier has shrunk by 2.6 ± 0.56 km2 (19.2 ± 4.1%) at a rate of 0.05 ± 0.01 km2 a−1 whereas, the Padam Glacier has shrunk by 3.4 ± 0.65 km2 (12.7 ± 2.4%) at a rate of 0.06 ± 0.01 km2 a−1. • The frontal recession of the glaciers was determined to be 1.240 ± 0.02 km (15.7 ± 2.0%) at a rate of 20 ± 0.4 m a−1 (Dalung Glacier) and 2.690 ± 0.5 m (21.3 ± 2.1%) at a rate of 50.7 ± 0.1 ma−1 (Padam Glacier). Consequently, the glacial lakes formed at the snout of the glaciers revealed an expansion of 0.28 ± 0.05 km2 (DL) and 0.41 ± 0.008 km2 (PL) from 1990 to 2015. • Glacial Lake Outburst Flood Modeling has been carried out for these vulnerable glacial lakes as determined by the integrated criteria of standard indices and the peak flood hydrographs at the Lake site and other vulnerable sites downstream have been computed. Abstract Glacier recession and formation of glacial lakes along with outburst flood hazards are increasing in response to changing climate in the Himalayan region. This study describes evolution of Dalung and Padam glaciers and their associated lakes employing multi-temporal datasets of Landsat (MSS, TM, ETM+), Indian Remote Sensing LISS-III, Google EarthTM, ASTER GDEM and Survey of India topographic maps. The Dalung Glacier (DG) and Lake (DL) are present in Suru River catchment whereas the Padam Glacier (PG) and Lake (PL) are present in Tsarap River catchment of Zanskar basin, western Himalaya. From 1962 to 2015; the DG and PG have shrunk at different rates. The DG has shrunk by 2.6 ± 0.56 km2 (19.2 ± 4.1%) at a rate of 0.05 ± 0.01 km2 a−1 whereas, the PG has shrunk by 3.4 ± 0.65 km2 (12.7 ± 2.4%) at a rate of 0.06 ± 0.01 km2 a−1. The frontal recession was recorded as 1.240 ± 0.02 km (15.7 ± 2.0%) at a rate of 20 ± 0.4 m a−1 for DG and 2.690 ± 0.5 m (21.3 ± 2.1%) at a rate of 50.7 ± 0.1 m a−1 for PG. Consequently, the proglacial glacial lakes have formed indicating an expansion of 20 ± 3.4% (DL) and 58 ± 4.5% (PL) during 1990–2015. Using integrated criteria of standard indices for the identification of potentially dangerous glacial lakes (PDGLs), the lakes were found to be vulnerable and have a potential to cause breaching in the coming years. In order to provide inputs for the emergency action plan, one dimensional MIKE 11 Model was used to generate the peak flood hydrographs at the lake and other vulnerable sites downstream. Highest peak discharge of 3361.7 m3 s−1 (DL) and 4210.3 m3 s−1 (PL) were estimated at the lake sites which has reduced to 1520.9 m3 s−1 and 1722.4 m3 s−1 respectively at the outlet sites. The reduced discharge at downstream sites still bears the potential to create dangerous flood hazards. [ABSTRACT FROM AUTHOR]

A case study of glacial lakes outburst flood (GLOF) hazard assessment by satellite Earth observation (EO) and numerical modelling is presented for the supraglacial and ice-contact lakes on Thangothang Chhu glacier, Chomolhari area (Bhutan). Detailed geomorphological mapping, including landslide and rock glacier inventories, as well as surface displacement determination using an interferometric SAR (InSAR) satellite, allowed a GLOF hazard assessment for lake Wa-007 to be performed. Outburst scenario modelling was achieved by combining both empirical and numerical modelling approaches, revealing that only a flood wave can have an impact on the two human settlements located downslope of Wa-007 lake. The worst-case scenario, modelled thanks to r.damflood, allowed the wave-front arrival time, the maximum water depth and the arrival time of maximum water height for the two human settlements to be quantified. A long-term monitoring strategy based entirely on EO data, with an update cycle of 5 years, is proposed to assess the future evolution of the area. [ABSTRACT FROM AUTHOR]

Summary The areas of glacial lakes in the Himalayas continue to increase alarmingly due to global warming with consequent risk of glacial lake outburst flood (GLOF). The outburst is most common for moraine-dammed lakes as a result of a failure of the dam by overtopping and erosion or piping due to seepage. In the present context, GLOF events, especially for the moraine dam failure process needs to be predicted to assess the drastic and detrimental impacts on the downstream river valley. This study focuses on validating an integrated model for simulating the failure of moraine dam by overtopping and erosion using a coupled numerical simulation model. The proposed numerical methodology is validated with the data from experiments in laboratory scale physical models. The results of the model are compared for both the erosional profiles during collapse of the dam and the resulting outflowing flood hydrograph. The primary finding is that the moraine dam height and the volume of the lake upstream of the dam are the most sensitive parameters influencing the GLOF peak. The model is also applied to the field problem of the Tangjiashan lake outburst and dam failure and shows reasonably good agreement with observations. The validated model is also run for the South Lhonak glacial lake in the Sikkim Himalayas, India to obtain the probable flood hydrograph in case of failure of the moraine dam. [ABSTRACT FROM AUTHOR]

Glacial lake outburst floods occurred frequently during the last deglaciation of the Laurentide Ice Sheet. Within the Interior Plains, these floods carved large spillway systems; however, due to a lack of abundant sediment, deposits within prairie spillways are rarely preserved. Here, we present geomorphic and sedimentary evidence and hydraulic modelling of the eastern Beaver River Spillway, formed by the catastrophic drainage of the ice‐dammed glacial Lake Algar, in north central Alberta. During this flood, coarse‐grained sediment eroded from local till formed large pendant bars. Within the first ~50 km of the spillway (Reach 1), pendant bars contain downstream orientated foresets overlain by horizontally bedded coarser gravels. The remaining pendant bars (Reach 2), present downflow of a moraine barrier, differ, comprising massive, matrix‐supported, inversely graded gravels capped by a boulder layer. We use a HEC‐GeoRAS/HEC‐RAS system in conjunction with palaeostage indicators to estimate the steady‐state water surface elevation. Modelling results show that peak discharge within Reach 1 of the eastern Beaver River Spillway was approximately 14 000–21 000 m3 s−1. For Reach 2, 30 km downstream, the peak discharge was estimated at 23 000–40 000 m3 s−1 (nbulked 18 000–26 000 m3 s−1). The downstream discharge increase, consistent with the sedimentary change in pendant bar deposits, is attributed to sediment bulking of the flood flow. This provides the opportunity to observe a range of flow conditions, and associated sedimentology, from a single flood event. The reconstructed flow conditions, coupled with lake volume estimates from the ponding above the moraine barrier suggest a minimum flow duration of 3–5 days. [ABSTRACT FROM AUTHOR]

Abstract Glacial Lake Outburst Floods (GLOFs) have become increasingly common over the past century in response to climate change, posing risks for human activities in many mountain regions. In this paper we document and reconstruct the sequence of events and impact of a large GLOF that took place in December 2015 in the Chileno Valley, Patagonia. Hydrograph data suggests that the flood continued for around eight days with an estimated total discharge of 105.6 × 106 m3 of water. The sequence of events was as follows: (1) A large debris flow entered the lake from two steep and largely non-vegetated mountain gullies located northeast of the Chileno Glacier terminus. (2) Water displaced in the lake by the debris flow increased the discharge through the Chileno Lake outflow. (3) Lake and moraine sediments were eroded by the flood. (4) Eroded sediments were redistributed downstream by the GLOF. The post-GLOF channel at the lake outlet widened in some places by >130 m and the surface elevation of the terrain lowered by a maximum of 38.8 ± 1.5 m. Farther downstream, large amounts of entrained sediment were deposited at the head of an alluvial plain and these sediments produced an ~340 m wide fan with an average increase in surface elevation over the pre-GLOF surface of 4.6 ± 1.5 m. We estimate that around 3.5 million m3 of material was eroded from the flood-affected area whilst over 0.5 million m3 of material was deposited in the downstream GLOF fan. The large debris flow that triggered the GLOF was probably a paraglacial response to glacier recession from its Little Ice Age limits. We suggest that GLOFs will continue to occur in these settings in the future as glaciers further recede in response to global warming and produce potentially unstable lakes. Detailed studies of GLOF events are currently limited in Patagonia and the information presented here will therefore help to inform future glacial hazard assessments in this region. [ABSTRACT FROM AUTHOR]

Abstract: More than 2000 of mountain lakes covering more than 0.1ha exist in a territory of Kyrgyzstan. Nearly 20% of them are dangerous because of instability of lake dams, frequent overflows and melting of buried ice inside the moraine dams. According to the Kyrgyz lake inventory, 328 lakes are at risk of outburst and 12 lakes are considered as actually dangerous. Since 1952 more than 70 disastrous cases of lake outbursts have occurred. The majority of the endangered lakes belong to one of the three genetic types: morainic-glacier, supraglacial and lake dammed by landslides and debris flows. Petrov, Adygine and Koltor lakes were selected and studied in the Tien-Shan Mountains as case studies of the most frequent genetic types of hazardous lakes. Observations were focused on the morphology of the lake basin and the surrounding relief, outflow pattern and processes controlling the development of lake. For the hazard assessment, evolution of glaciers and lakes was reconstructed using historical reports, aerial photographs and satellite images. [Copyright &y& Elsevier]

[Display omitted] • We propose a framework for the identification and assessment of unreported GLOFs. • The framework was successfully applied for Zalai Tsho GLOF. • We reported the Zalai Tsho GLOF on July 7, 2018, in Bomi County for the first time. • The evolution, impact and process related to Zalai Tsho GLOF were analyzed. 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. [ABSTRACT FROM AUTHOR]

Glacier-associated hazards are becoming a common and serious challenge to the high mountainous regions of the world. Glacial lake outburst floods (GLOFs) are one of the most serious unanticipated glacier hazards, with the potential to release a huge amount of water and debris in a short span of time, resulting in the loss of lives, property, and severe damage to downstream valleys. The present study used multi-temporal Landsat and Google earth imageries to analyze the spatio-temporal dynamism of the selected glacial lake (moraine-dammed) in the Satluj basin of Western Himalayas. Furthermore, GLOF susceptibility of the lake was assessed using a multi-criteria decision-based method. The results show that the lake area has increased from 0.11 to 0.26 km2 over the past 28 years from 1990 to 2018. The susceptibility index value for the lake was calculated as 0.75, which indicates that the lake is highly susceptible to the GLOF. The depth and volume of the lake were estimated to be 16 m and 57 × 105 m3, respectively, using an empirical formula. HEC-RAS, HECGeo-RAS, and Arc-GIS software were utilized in this study to perform unsteady flow analysis and to determine the GLOF impact on the downstream area. The worst-case GLOF scenario (breach width of 75 m) was revealed during an overtopping failure of the moraine dam, resulted in a peak discharge of 4060 m3/s and releasing a total water volume of 57 × 105 m3. The breach hydrograph has been routed to calculate the spatial and temporal distribution of peak flood, inundation depth, velocity, water surface elevation, and flood peak arrival time along the river channel. The analysis further reveals that the routed flood waves reach the nearest settlement, i.e., Rajpur town, situated at a distance of 102 km in the downstream valley of the lake at 6 h after the beginning of the lake breach event with a peak discharge/flood of 1757 m3/s and maximum flow velocity of 1.5 m/s. With the ongoing climate warming and glacier retreat, moraine-dammed lakes are becoming more hazardous and thus increasing the total threat. Therefore, it is mandatory to monitor and assess such lakes at regular intervals of time to lessen the disastrous impacts of GLOFs on the livelihood and infrastructure in the downstream valleys. The findings of this study will aid in the creation of risk management plans, preparatory tactics, and risk reduction techniques for GLOF hazards in the region. [ABSTRACT FROM AUTHOR]

In this paper we present a suite of erosional remnants, mega deposits and subtle bar morphology that we relate to the outburst flood from the glacial lake Nedre Glomsjø at the end of the last Ice Age. By using large datasets of airborne LiDAR data implemented in a geographic information system (GIS), we have mapped flood related features along the Glomma and Vrangselva rivers in southeastern Norway. The unprecedented overview of the valley reaches obtained by the vegetation-free LiDAR-derived digital elevation models (DEM) has revealed a set of hitherto undocumented landforms. Persisting erosive lines – indicators of the uppermost flooded level – are carved into surficial deposits in the hillsides and are found as high as 80–90 m above the modern valley floor. By using the indicators as an upper flood boundary, we have computed cross-sectional profiles showing that the flood in some reaches inundated more than 120 000 m 2 of the valley. Large, streamlined bed forms, which we interpret as flood bars, drape sections of the valley floor, some several kilometers long. The most morphologically striking – pendant bars – are developed behind flood flow projections, such as bedrock knolls or in lee of a valley bend. Flood bars occur in the entire study area, but are more widespread in the north and generally decrease in size moving in a downstream direction. Kettle holes and ice-block obstacle marks from icebergs arrested during the flood are common. These features support the theory of a catastrophic drainage event, but also indicate a pattern of differential erosion and deposition that allowed us to interpret palaeoflow on individual bars. Vast aeolian dune fields in the region are interpreted as a secondary product of the flood, as deposits related to the event were mobilised by northerly winds momentarily after the flood waned. The dune fields cover an excess of 50 km 2 and reveal that the region was a highly active periglacial desert after the flood. Our mapping highlights the outburst flood's role as a landscape-defining event. Morphological evidence determine the southern fringe of the Scandinavian ice sheet to c. 15 km north of Elverum at the time of the outburst flood. From calibrating existing 14 C dates we postulate an age of c. 10–10.4 cal ka BP for the Nedre Glomsjø drainage event and the contemporaneous margin of the ice sheet. [ABSTRACT FROM AUTHOR]

Abstract: A prominent lake formed when glaciers descending from the Kodar Range blocked the River Vitim in central Transbaikalia, Siberia. Glacial Lake Vitim, evidenced by palaeoshorelines and deltas, covered 23,500km2 and held a volume of ~3000km3. We infer that a large canyon in the area of the postulated ice dam served as a spillway during an outburst flood that drained through the rivers Vitim and Lena into the Arctic Ocean. The inferred outburst flood, of a magnitude comparable to the largest known floods on Earth, possibly explains a freshwater spike at ~13calka BP inferred from Arctic Ocean sediments. [Copyright &y& Elsevier]

Background: Glaciers of the Hindu Kush region are highly susceptible to climate change. Recently, a severe glacial lake outburst flood (GLOF) hit the supraglacial region at the frontier of Dook Pal Glacier. Information on the bacterial community in a freshly appeared supraglacial lake after GLOF is essential to probe the bacterial distribution pattern after immediate unlocking from the supraglacial region. After GLOF, geochemistry and bacterial diversity, distribution, community structure, and function were examined in the lake-debris and melt-water. Results: In general, concentrations of dissolved free amino acids were similar between lake-debris and melt-water, potentially toxic elements and cations were greater in lake-debris, and anions concentrations were greater in melt-water. In addition, there was comparable diversity in the glacial melt-water and lake-debris; Proteobacteria dominated in lake-debris (33.1–94.5%), while Proteobacteria (36.7–50.5%) and Firmicutes (44–62%) dominated in melt-water. It is more likely that Proteobacteria and Firmicutes shifted towards melt-water after GLOF, creating an uneven distribution of communities in the lake-debris; however, a relatively even distribution was maintained in melt-water. Genes responsible for metabolism and energy production were higher in lake-debris than in melt-water bacteria; whereas, genes for other cellular mechanisms were higher in melt-water than in lake-debris bacteria. Conclusions: This study offers valuable datasets in understanding the bacterial diversity, distribution and function as a consequence of GLOF at the glacial frontier. [ABSTRACT FROM AUTHOR]

Geomorphological mapping, sedimentology, lichenometry and dendrochronology were used to assess the nature and timing of glacier recession, moraine development and catastrophic mass movements in a tributary of the Leones valley, east of the Hielo Patagónico Norte, Chile. We show that during the 'Little Ice Age' Glaciar Calafate advanced downvalley to produce a terminal moraine. Recession of the glacier from this position occurred in the 1870s and produced a moraine dammed lake. In late 2000 a large rockfall into the lake breached the moraine and triggered a glacial lake outburst flood (GLOF) that entrained and subsequently deposited some 2 × 106 m3 of material. We interpret this event as a delayed paraglacial response to the retreat of Glaciar Calafate during the twentieth century. [ABSTRACT FROM AUTHOR]

The retreating behavior of glaciers observed in most of the Hindu Kush–Karakoram–Himalaya (HKH) region has given rise to the formation and expansion of numerous glacial lakes in the region. The lakes expansion under changing climate usually poses high risk of glacial lake outburst flood (GLOF) hazard for the downstream communities. In the present study, the risk of glacial lake outburst flood was investigated in the HKH region of Pakistan using LANDSAT-8 OLI (Operational Land Imager) image data of 2013 period coupled with ground information. The results of present study revealed 3044 lakes (surface area about 134.8 km2) in the three HKH ranges, maximum in the Karakoram (1325) and minimum in the Hindu Kush range (722) during 2013. The lakes exhibited an overall increase of about 26% in number and 7% in area in the region during 2001–2013 period. The increase in lake number was 91% within 2500–3500 m, 20% within 3500–4500 m and 31% within 4500–5500 m elevation range. Among total identified lakes during 2013, 36 were characterized as potentially dangerous glacial lakes (PDGLs) that can pose GLOF hazard in the HKH region. A regular monitoring of cryosphere changes and critical glacial lakes is essential to develop sustainable risk management strategies for this region in future. [ABSTRACT FROM AUTHOR]