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In this study, a glacial lake-outburst flood was documented in the immediate foreland of the maximum phase of the Wartanian (Warthian, Late Saalian, MIS 6) Glaciation at Adamow in south central Poland. The structural and textural analyses of the sediments, as well as palaeohydraulic analysis, were carried out in the proximal part of the outwash plain where a fragment of the floodwater drainage system comprising buried erosional channels have been documented. Their fill reached a thickness of up to 11 m and was composed of poorly sorted, massive gravels with boulders, as well as horizontally, sub-horizontally, low-angle, and cross-stratified gravels. The coarse sediments were found to be inversely and normally graded. These sediments constituted the records of two subsequent flooding episodes. In the channel fill, the lenticular accumulations of gravel were identified and interpreted as buried large gravel dunes, while exhibiting a thickness of up to 2.5 m. Traces of sediment diapirism at the contact of channel fill and underlying sediments were also documented. Deformation was observed to originate from liquefaction caused by the rapid depositional loading of flood deposits. The example used in this study exhibited that the impact of glacial lake-outburst floods in shaping the marginal zones and foreland of ice sheets in the North European Plain was higher than that considered earlier. This example also showed a different case of glacial outburst flood in the foreland of the Middle Pleistocene ice sheets of Europe than that already known, which includes the discharge of sub- or englacial meltwater reservoirs emanated from a large proglacial ice-dammed lake.

The Arctic regions experience intense transformations, such that efficient methods are needed to monitor and understand Arcticlandscape changes in response to climate warming and low-frequency high-magnitude 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 glaciallake outburst affected the Zackenberg River (NE Greenland). Here, we provided a very high-resolution dataset representingunique 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): https://doi.org/10.5281/zenodo.4495282 (Tomczykand 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 mappingin vector formats: https://doi.org/10.5281/zenodo.4498296 (Tomczyk and Ewertowski, 2021b). Potential applications of thepresented dataset include: (1) assessment and quantification of landscape changes as an immediate result of glacier lakeoutburst 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 ofgeohazards related to bank erosion and debris flow development (hazards for research station infrastructure – station buildingsand bridge); (5) monitoring of permafrost degradation; and (6) modelling flood impacts on river ecosystem, transport capacity,and channel stability. &nbsp

A potential glacial lake outburst flood from Lake Palcacocha (Cordillera Blanca, Peru) threatens Huaraz, a city of 120,000 people. In 1941, an outburst flood destroyed one-third of the city and caused at least 1,800 fatalities. Since pre-industrial times, Lake Palcacocha has expanded due to the retreat of Palcaraju glacier. Here we used observations and numerical models to evaluate the anthropogenic contribution to the glacier’s retreat and glacial lake outburst flood hazard. We found that the magnitude of human-induced warming equals between 85 and 105% (5–95% confidence interval) of the observed 1 °C warming since 1880 in this region. We conclude that it is virtually certain (>99% probability) that the retreat of Palcaraju glacier to the present day cannot be explained by natural variability alone, and that the retreat by 1941 represented an early impact of anthropogenic greenhouse gas emissions. Our central estimate is that the overall retreat is entirely attributable to the observed temperature trend, and that the resulting change in the geometry of the lake and valley has substantially increased the outburst flood hazard. Human-induced warming is responsible for the retreat of Palcaraju glacier and the associated increase in glacial lake outburst flood hazard, according to an analysis of observations and numerical models.

The Kangri Karpo Mountain Range on the Qinghai-Tibet Plateau frequently experiences glacial lake outburst floods (GLOFs). This study assessed the risk of outburst floods for Guangxieco Proglacial Lake (GPL) in this Mountain Range as a typical case to reveal the effects of rapid glacial change. The area of Gongzo Glacier behind GPL decreased by 7.39 ± 0.10% from 1987 to 2019, while this glacier advanced by 32.45 m from 5 June to 27 October in 1988. Guangxieco Proglacial Lake decreased from 0.42 ± 0.03 km2 in 1987 to 0.19 ± 0.03 km2 in 1988 and then continuously expanded to 0.43 ± 0.04 km2 in 2019. Heavy precipitation occurred before 15 July 1988, when no supraglacial lake existed. Meanwhile, sustained abnormally high air temperature caused accelerated glacier and snow melting. Since 1988, a larger volume of rainfall and meltwater impounded by the ice wall caused an increase in the basal water pressure in the glacier. A significant increase in winter mass balance has caused a further increase in the downward gravity component of glacier sliding. As a result, the glacier advanced rapidly while reopening previously blocked subglacial drainage systems. The accumulating subglacial water rapidly drained into the Proglacial Lake causing an elevated lake level and a GLOF event. However, the current area of the glacial lake has recovered to the scale present before the outburst in 1988. Therefore, local government agencies and the local community should improve early warning systems and take measures designed to prevent a new GLOF and to minimize the risk of a recurrence of a GPL outburst.

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.

Shishper lake is an ice-dammed lake in northern Pakistan that has drained twice within one (1) year. The parameters evaluated in this paper are the lake’s area, volume, peak discharge, and its outburst events using various satellite images from November 2018 to June 2020. Based on satellite imagery and empirical approaches, the lake formed in November 2018 and reached a maximum of 0.34 km2 till its first breach that occurred on 22 June 2019. Since June 2019, the lake drained till September 2019. After that, the flow was blocked again, and the lake expanded to an area of 0.27 km2 till its second outburst event that happened on May 29, 2020. Eight cross-sectional profiles of Hassanabad ravine are generated based on peak discharge in the lake’s rapid outburst. The results indicate that, the peak discharge for both 2019 and 2020 was more than 4500 m3 s−1. Delineation of downstream Hassanabad ravine shows that more than 1000 buildings and 2000+ population is prone to flood. However, the lake drain twice steadily, but it has a high potential to cause severe damages if it bursts abruptly.

Glacial lake outburst flood (GLOF) is one of the major natural disasters in the Qinghai-Tibetan Plateau (QTP). On 25 June 2020, the outburst of the Jiwenco Glacial Lake (JGL) in the upper reaches of Nidu river in Jiari County of the QTP reached the downstream Niwu Township on 26 June, causing damage to many bridges, roads, houses, and other infrastructure, and disrupting telecommunications for several days. Based on radar and optical image data, the evolution of the JGL before and after the outburst was analyzed. The results showed that the area and storage capacity of the JGL were 0.58 square kilometers and 0.071 cubic kilometers, respectively, before the outburst (29 May), and only 0.26 square kilometers and 0.017 cubic kilometers remained after the outburst (27 July). The outburst reservoir capacity was as high as 5.4 million cubic meters. The main cause of the JGL outburst was the heavy precipitation process before outburst and the ice/snow/landslides entering the lake was the direct inducement. The outburst flood/debris flow disaster also led to many sections of the river and buildings in Niwu Township at high risk. Therefore, it is urgent to pay more attention to glacial lake outburst floods and other low-probability disasters, and early real-time engineering measures should be taken to minimize their potential impacts.

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...

We report previously unpublished evidence for a Marine Isotope Stage 3 (MIS 3; 60–26 ka) glacial outburst flood in the Torngat Mountains (northern Quebec/Labrador, Canada). We present 10Be cosmogenic exposure ages from legacy fieldwork for a glacial lake shoreline with evidence for outburst flooding in the Torngat Mountains, with a minimum age of 36 ± 3 ka (we consider the most likely age, corrected for burial, to be ~56 ± 3 ka). This shoreline position and age can potentially constrain the Laurentide Ice Sheet margin in the Torngat Mountains. This region, considered a site of glacial inception, has no published dated geologic constraints for high-elevation MIS 3 ice margins. We estimate the freshwater flux associated with the inferred glacial outburst flood using high-resolution digital elevation maps corrected for glacial isostatic adjustment. Using assumptions about the ice-dammed locations we find that a freshwater flood volume of 1.14 × 1012 m3 could have entered the Hudson Strait. This glacial outburst flood volume could have contributed to surface ocean freshening to cause a measurable meltwater signal in δ18O records, but would not necessarily have been associated with substantial ice rafted debris. Future work is required to refine estimates of the size and timing of such a glacial outburst flood. Nevertheless, we outline testable hypotheses about the Laurentide Ice Sheet and glacial outburst floods, including possible implications for Heinrich events and glacial inception in North America, that can be assessed with additional fieldwork and cosmogenic measurements.

Glaciers respond sensitively to climate variability and change, with associated impacts on meltwater production, sea-level rise and geomorphological hazards. There is a strong societal interest to understand the current response of all types of glacier systems to climate change and how they will continue to evolve in the context of the whole glacierized landscape. In particular, understanding the current and future behaviour of debris-covered glaciers is a ‘hot topic’ in glaciological research because of concerns for eater resources and glacier-related hazards. The state of these glaciers is closely related to various hazardous geomorphological processes which are relatively poorly understood. Understanding the implications of debris-covered glacier evolution requires a systems approach. This includes the interplay of various factors such as local geomorphology, ice ablation patterns, debris characteristics, glacier lake growth and development. Such a broader, contextualized understanding is prerequisite to identifying and monitoring the geohazards and hydrologic implications associated with changes in the debris-covered glacier system under future climate scenarios. This paper presents a comprehensive review of current knowledge of the debris-covered glacier landsystem. Specifically, we review state-of-the-art field and remote sensing-based methods for monitoring debris-covered glacier characteristics and lakes and their evolution under future climate change. We advocate a holistic process-based framework for assessing hazards associated with moraine-dammed glacio-terminal lakes that are a projected end-member state for many debris-covered glaciers under a warming climate.

Against the background of climate change-induced glacier melting, numerous glacial lakes are formed across high mountain areas worldwide. Existing glacial lake inventories, chiefly created using Landsat satellite imagery, mainly relate to 1990 onwards and relatively long (decadal) temporal scales. Moreover, there is a lack of robust information on the expansion and the GLOF hazard status of glacial lakes in the Bhutan Himalaya. We mapped Bhutanese glacial lakes from the 1960s to 2020, and used these data to determine their distribution patterns, expansion behavior, and GLOF hazard status. 2,187 glacial lakes (corresponding to 130.19 ± 2.09 km2) were mapped from high spatial resolution (1.82–7.62 m), Corona KH-4 images from the 1960s. Using the Sentinel-2 (10 m) and Sentinel-1 (20 m × 22 m), we mapped 2,553 (151.81 ± 7.76 km2), 2,566 (152.64 ± 7.83 km2), 2,572 (153.94 ± 7.83 km2), 2,569 (153.97 ± 7.79 km2) and 2,574 (156.63 ± 7.95 km2) glacial lakes in 2016, 2017, 2018, 2019 and 2020, respectively. The glacier-fed lakes were mainly present in the Phochu (22.63%) and the Kurichu (20.66%) basins. A total of 157 glacier-fed lakes have changed into non-glacier-fed lakes over the 60 years of lake evolution. Glacier-connected lakes (which constitutes 42.25% of the total glacier-fed lake) area growth accounted for 75.4% of the total expansion, reaffirming the dominant role of glacier-melt water in expanding glacial lakes. Between 2016 and 2020, 19 (4.82 km2) new glacial lakes were formed with an average annual expansion rate of 0.96 km2 per year. We identified 31 lakes with a very-high and 34 with high GLOF hazard levels. These very-high to high GLOF hazard lakes were primarily located in the Phochu, Kurichu, Drangmechu, and Mochu basins. We concluded that the increasing glacier melt is the main driver of glacial lake expansion. Our results imply that extending glacial lakes studies back to the 1960s provides new insights on glacial lake evolution from glacier-fed lakes to non-glacier-fed lakes. Additionally, we reaffirmed the capacity of Sentinel-1 and Sentinel-2 data to determine annual glacial lake changes. The results from this study can be a valuable basis for future glacial lake monitoring and prioritizing limited resources for GLOF mitigation programs.

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.

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.

The existence of numerous lakes in the higher reaches of the Himalaya makes it a potential natural hazard as it imposes a risk of glacial lake outburst flood (GLOF), which can cause great loss of life and infrastructure in the downstream regions. Hydrodynamic modeling of a natural earth-dam failure and hydraulic routing of the breach hydrograph allow us to characterize the flow behavior of a potential flood along a given flow channel. In the present study, the flow hydraulics of a potential GLOF generated due to the moraine failure of the Satopanth lake located in the Alaknanda basin is analyzed using one-dimensional and two-dimensional hydrodynamic computations. Field measurements and mapping were carried out at the lake site and along the valley using high-resolution DGPS points. The parameters of Manning’s roughness coefficient and terrain elevation were derived using satellite-based raster, the accuracy of which is verified using field data. The volume of the lake is calculated using area-based scaling method. Unsteady flood routing of the dam-break outflow hydrograph is performed along the flow channel to compute hydraulic parameters of peak discharge, water depth, flow velocity, inundation and stream power at a hydropower dam site located 28 km downstream of the lake. Assuming the potential GLOF event occurs contemporaneously with a 100-year return period flood, unsteady hydraulic routing of the combined flood discharge is performed to evaluate its impact on the hydropower dam. The potential GLOF resulted in a peak discharge of ~ 2600 m3s−1 at the dam site which arrived 38 min after the initiation of the moraine-failure event. The temporal characteristics of the flood wave analyzed using 2D unsteady simulations revealed maximum inundation depth and flow velocity of 7.12 m and 7.6 ms−1, respectively, at the dam site. Assuming that the control gates of the dam remain closed, water depth increases at a rate of 4.5 m per minute and overflows the dam approximately 4 min after the flood wave arrival.

Accurate prediction of the hydrographs of outburst floods induced by landslide dam overtopping failure is necessary for hazard prevention and mitigation. In this study, flume model tests on the breaching of landslide dams were conducted. Unconsolidated soil materials with wide grain size distributions were used to construct the dam. The effects of different upstream inflow discharges and downstream bed soil erosion on the outburst peak discharge were investigated. Experimental results reveal that the whole hydrodynamic process of landslide dam breaching can be divided into three stages as defined by clear inflection points and peak discharges. The larger the inflow discharge, the shorter the time it takes to reach the peak discharge, and the larger the outburst flood peak discharge. The scale of the outburst floods was found to be amplified by the presence of an erodible bed located downstream of the landslide dam. This amplification decreases with the increase of upstream inflow. In addition, the results show that the existence of an erodible bed increases the density of the outburst flow, increasing its probability of transforming from a sediment flow to a debris flow.

Two large landslides in October and November 2018 sequentially dammed the Jinsha river at Baige village, eastern Tibet, China. Subsequently, breaching of each dam induced massive outburst floods that posed a severe threat to downstream cities and infrastructure. Field investigation indicates volumes of the first and second landslide dam are about 24.5 × 106 m3 and 8.53 × 106 m3, respectively. However, the peak discharge of the flood generated from the second landslide (3.1 × 104 m3/s) was significantly larger than that from the first (1.0 × 104 m3/s). The second peak discharge would have been 5.15 × 104 m3/s if the dam breached naturally. In this study, we developed two geometry parameters: effective dam height He (elevation difference between overtopping level and river bottom) and a narrowing number distribution Nr(H) (measures the degree to which a river section is occupied by landslide materials to elevation H) which represents river section narrowing effects of successive landslides. Using numerical simulations, we show that He dominates peak discharge, and it has a linear relationship with peak discharge with slope of 1009.4 m2/s. Furthermore, the dam includes two sub-areas: a higher part (SB-1) and a lower part (SB-2). Two floods only eroded SB-2. However, breaching of SB-1 and breached SB-2 still narrowed the river. The narrowing effects of the first and second breached dam on the river channel are around 0.35 and 0.5, respectively. Spillway and landslide runup deposits increased the local flood risk by narrowing and lifting the local river section; the first landslide promoted the second landslide, which occupied the same area and forms a dam with high He value. Consequently, a more catastrophic flood could be triggered by a small subsequent landslide. Spatial superposition phenomenon of successive landslides increased the local flood risk. This research quantitatively analyzed the influence of the geometry of dam induced by successive landslides on the process of outburst floods and the risk.

Rainforest rivers export large quantities of terrestrial materials from watersheds to the coastal ocean, with important implications for local ecosystems and global biogeochemical cycles. However, the impact of episodic disturbance on this process is a critical knowledge gap in our understanding of land-sea connections. Fjords represent a global hotspot for terrestrial carbon burial in marine sediments, yet the relative importance of typical riverine fluxes vs. mass wasting fluxes is uncertain and dynamic. Similarly, mass wasting events can generate both an instantaneous pulse and a sustained shift in the material export regime. Riverine sediment regimes also have important implications for freshwater ecosystems and fisheries resources. A recent mass wasting event in Bute Inlet – Homalco First Nation traditional territory and British Columbia, Canada – presents an important opportunity to quantify the sustained impact of such an infrequent large disturbance on the source-to-sink linkages between glacierized mountains, rivers, and fjords.On November 28, 2020, a landslide in the headwaters of the Elliot Creek watershed (118 km2) triggered a glacial lake outburst flood (GLOF) that eroded 3 km2 of forested land and exported large volumes of water and terrestrial materials to the lower reaches of the Southgate River watershed (1986 km2) and ultimately to the head of Bute Inlet. Here we assess river and ocean surface turbidity over four winter months following the event, in comparison to pre-event measurements taken across all seasons in recent years. River turbidity was measured on the Southgate River above and below the confluence of Elliot Creek, beginning in December 2020, and at the mouth of the Southgate and nearby Homathko Rivers prior to November 2020. Bute Inlet turbidity was measured (every month to two months) starting in May 2017.Prior to the GLOF event, Southgate River turbidity ranged from a low of 3.3 ± 0.4 FNU in the winter to a high of 71.4 FNU in the summer meltwater period. Since the event, Southgate River turbidity has been consistently elevated ≥6 times background levels recorded above Elliot Creek. At the extreme, on January 13, 2021, seven weeks after the GLOF, Southgate River mean turbidity (105.2 ± 3.3 FNU) was 32 times the background (3.3 ± 0.4 FNU), equating to a sustained increase in wintertime turbidity that sometimes exceeds the historical summertime peak. Given the typical coupling of turbidity with discharge, we expect further increases in turbidity with the coming freshet of 2021; the first meltwater season following the GLOF. These results suggest the potential for a sustained shift in the seasonal turbidity regime of the Southgate River and the estuarine waters of Bute Inlet. The elevated turbidity signals broader changes to: sediment export and carbon burial, the depth and seasonality of light penetration, river water quality, and spawning habitat quality for anadromous fish. Ongoing monitoring will be used to characterize the duration, dynamics, and potential recovery of elevated turbidity regimes across the land-to-ocean aquatic continuum in Bute Inlet.

The glaciers in the Himalayan region are nature's valuable source of fresh water and these frozen reservoirs release large amounts of ice melt water to many of the major rivers of this region. Rapid accumulation of water in the glacial lakes can lead to a sudden breach of their unstable moraine ‘dams’. The resultant discharges of huge amounts of water and debris - a Glacial Lake Outburst Flood (GLOF)/Flash Flood - often have catastrophic effects downstream. The Centre for Development of Advanced Computing (C-DAC) has developed ultrasonic sensor based monitoring system, which continuously records the fluctuations in water level as well as the ice thickness which forms over the lake surface. The sensor electronics is in link with Satellite through DRT payload of INSAT-3C. This is first-of-its-kind system in the country and will be a great boon to the nation in the area of disaster forecast and management. Currently, the system is deployed at Shako Chho (4987 m above msl) and Kupup Chho (3982 m above msl) glacial lakes.

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.

The presence of large and rapidly growing glacial lakes along the Himalayan Arc makes glacial lake outburst floods (GLOFs) a serious mountain hazard. While glacial lakes are mainly located in remote and unsettled mountain valleys, far-reaching GLOFs may claim lives and damage assets tens of kilometers downstream. Evaluating GLOF hazard is therefore of high importance, considering current and potential future climate-driven changes of glaciers and glacial lakes. A major concern in the Northeastern Indian Himalayan state of Sikkim is the damage potential these flood events can cause to hydropower plants and local vulnerable communities. This is particularly true for outburst floods potentially originating from the two lakes in Sikkim that are considered hazardous: the South Lhonak Lake and the Shako Cho Lake. Both lakes have been recognized in previous studies, and by local and state authorities, as being high priority sites for further monitoring and potential risk reduction measures. Recognizing the need for related risk reduction strategies to be based on robust scientific understanding, this study aims to combine remote sensing approaches with hydrodynamic flood modeling to identify key threats to lives and livelihoods.This study also provides the first implementation of recently developed national guidelines on the management of GLOFs, where a detailed risk assessment including potential GLOF triggers, conditioning factors, and downstream impacts forms the scientific core. First results of only-water flow using HEC-RAS show that a high-potential scenario (dam breach depth = 40 m) produces flow depth and flow velocity up to 25 m and 9-12 m s-1, respectively, at Chungthang, a town located close to a major hydropower station, 62 km downstream of the lake. The fact that GLOF flow rheology is often changing as it propagates downstream, further modeling has been undertaken with r.avaflow, which can simulate the entire process chain from initial avalanche triggering, to dam erosion, and downstream flow propagation with a multi-phase modeling approach. Hence, we can evaluate the potential downstream impact in the case of a GLOF transitioning into a debris flow process. Our results provide flow hydraulics including flow velocities, flow heights, and total downstream inundation. These parameters will provide important insights for risk reduction strategies, such as early warning systems and land-use planning under current and future glacial conditions.

Glacial Lake Outburst Floods (GLOFs) constitute a major hazard in periglacial environments. Despite a recent increase in the size and number of glacial lakes worldwide, there is only limited evidence that climate change is affecting GLOF frequency. In Patagonia, GLOFs are particularly common in the Baker River watershed (47°S), where 21 GLOFs occurred between 2008 and 2017 due to the drainage of Cachet 2 Lake into the Colonia River, a tributary of the Baker River. During these GLOFs, the increased discharge from the Colonia River blocks the regular flow of the Baker River, resulting in the inundation of the Valle Grande floodplain, which is located approximately 4 km upstream of the confluence. To assess the possible long-term relationship between GLOF frequency, glacier behavior, and climate variability, four sediment cores collected in the Valle Grande floodplain were analyzed. Their geophysical and sedimentological properties were examined, and radiocarbon-based age-depth models were constructed. All cores consist of dense, fine-grained, organic-poor material alternating with low-density organic-rich deposits. The percentage of lithogenic particles, which were most likely deposited during high-magnitude GLOFs, was used to reconstruct the flood history of the last 2.75 kyr. Results show increased flood activity between 2.57 and 2.17 cal kyr BP, and between 0.75 and 0 cal kyr BP. These two periods coincide with glacier advances during the Neoglaciation. Our results suggest that GLOFs are not a new phenomenon in the region. Although rapid glacier retreat is likely responsible for high GLOF frequency in the 21st century, high-magnitude GLOFs seem to occur more frequently when glaciers are larger and thicker.

Glacial Lake Outburst Floods (GLOFs) are an increasing threat to Patagonian environments and communities. Here, we investigate the geomorphological and hydrological impact of a recent GLOF from Pascua River, which discharges at the head of Baker Fjord (Chile, 48°S). To do so, a sediment core was taken ~4 km offshore of the Pascua River mouth at a water depth of 248 m. The coring site is located on the flank of a submarine channel incised trough the subaquatic delta of Pascua River, 30 m above the bottom of the channel. The sediment physical and chemical properties were analysed at high resolution with X-ray CT, MSCL and XRF core scanning, in combination with lower resolution grain-size and bulk organic geochemistry measurements, and a core chronology was established using downcore variations in 137Cs activity. In addition, historical maps and satellite imagery of the past century were examined in combination with multibeam bathymetry of Baker Fjord to aid the interpretation of the sediment record.Results show that the sediments are composed of two distinct units separated by a 5-cm thick event deposit dated 1945±9 CE. Below the event, the sediment consists of coarse silt and fine sand, likely representing sediment deposition from turbidity currents. Above it, it consists of very fine silts, likely representing settling from the surficial sediment plume. Historical evidence shows that the event deposit corresponds to a ~256 106 m3 GLOF from Bergues Lake, the proglacial lake of Lucia Glacier that discharges directly into Pascua River. Before 1945, historical information shows that Pascua River drained via two active river branches that were most likely connected to the two submarine channels visible in the bathymetry of the subaquatic delta. After 1945, only the western river branch appears active, which likely caused the abandonment of the eastern submarine channel near which the sediment core was taken. Therefore, we hypothesize that the 1945 Bergues Lake GLOF caused the abandonment of the eastern river branch and submarine channel, which explains the absence of coarse-grained sediments in our sediment record after 1945±9 CE.This study provides the first report of a GLOF from the northeastern part of the Southern Patagonian Icefield, and it demonstrates that GLOFs can have long-term impacts on the hydrology of fjord-river systems.

The China-Pakistan Economic Corridor (CPEC) passes through the Hunza River basin of Pakistan. The current study investigates the creation and effects of end moraine, supra-glacial, and barrier lakes by field visits and remote sensing techniques along the CPEC in the Hunza River basin. The surging and moraine type glaciers are considered the most dangerous type of glaciers that cause Glacial Lake Outburst Floods (GLOFs) in the study basin. It can be concluded from the 40 years observations of Karakoram glaciers that surge-type and non-surge-type glaciers are not significantly different with respect to mass change. The recurrent surging of Khurdopin Glacier resulted in the creation of Khurdopin Glacial Lake in the Shimshal valley of the Hunza River basin. Such glacial lakes offer main sources of freshwater; however, when their dams are suddenly breached and water drained, catastrophic GLOFs appear and pose a great threat to people and infrastructure in downstream areas. This situation calls for an in-depth study on GLOF risks along the CPEC route and incorporation of GLOF for future policy formulation in the country for the CPEC project so that the government may take serious action for prevention, response to GLOFs, and rehabilitation and reconstruction of the areas.

When utilizing a finite volume method to predict outburst flood evolution in real geometry, the processing of wet-dry front and dry cells is an important step. In this paper, we propose a new approach to process wet-dry front and dry cells, including four steps: (1) estimating intercell properties, (2) modifying interface elevation, (3) calculating dry cell elevations by averaging intercell elevations, and (4) changing the value of the first term of slope limiter based on geometry in dry cells. The Harten, Lax, and van Leer with the contact wave restored (HLLC) scheme was implemented to calculate the flux. By combining the MUSCL (Monotone Upstream&ndash, centred Scheme for Conservation Laws)-Hancock method with the minmod slope limiter, we achieved second-order accuracy in space and time. This approach is able to keep the conservation property (C-property) and the mass conservation of complex bed geometry. The results of numerical tests in this study are consistent with experimental data, which verifies the effectiveness of the new approach. This method could be applied to acquire wetting and drying processes during flood evolution on structured meshes. Furthermore, a new settlement introduces few modification steps, so it could be easily applied to matrix calculations. The new method proposed in this study can facilitate the simulation of flood routing in real terrain.

This paper presents an inventory of lakes in the Central Andes region (31°–36° S) of Argentina by using high resolution satellite images. Lakes were classified according to the damming processes or associated landforms. Statistical analysis of main lakes attributes was carried out showing that larger lakes are associated with volcanic and karstic landforms, while smaller ones correspond to thermokarst supraglacial lakes. Lake distribution is forced by the regional topography being mainly located in the periglacial and glacial environment (above the 3730 m a.s.l.). Moreover, latitudinal distribution of different types of lakes differs. Larger water bodies in the Argentinean Central Andes are landslides dammed except to the 34°–35° S volcanic region. These findings set the first step in hazard analysis and highlight the need for carrying out further research to assess outburst flood hazard in the Arid Central Andes of Argentina.

In this study, the Glacier Lake Outburst Flood (GLOF) that occurred over Kedarnath in June 2013 was modeled using integrated observations from the field and Remote Sensing (RS). The lake breach parameters such as area, depth, breach, and height have been estimated from the field observations and Remote Sensing (RS) data. A number of modelling approaches, including Snow Melt Runoff Model (SRM), Modified Single Flow model (MSF), Watershed Management System (WMS), Simplified Dam Breach Model (SMPDBK) and BREACH were used to model the GLOF. Estimations from SRM produced a runoff of about 22.7 m3 during 16–17, June 2013 over Chorabari Lake. Bathymetry data reported that the lake got filled to its maximum capacity (3822.7 m3) due to excess discharge. Hydrograph obtained from the BREACH model revealed a peak discharge of about 1699 m3/s during an intense water flow episode that lasted for 10–15 minutes on 17th June 2013. Excess discharge from heavy rainfall and snowmelt into the lake increased its hydrostatic pressure and the lake breached cataclysmically.

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.

Glacial lake outburst floods (GLOF) evolve into debris flows by erosion and sediment entrainment while propagating down a valley, which highly increases peak discharge and volume and causes destructive damage downstream. This study focuses on GLOF hazard assessment in the Bhote Koshi Basin (BKB), where was highly developed glacial lakes and was intensely affected by the Gorkha earthquake. A new 2016 glacial lake inventory was established, and six unreported GLOF events were identified with geomorphic outburst evidence from GaoFen-1 satellite images and Google Earth. A new method was proposed to assess GLOF hazard, in which large numbers of landslides triggered by earthquake were considered to enter into outburst floods enlarge the discharge and volume of debris flow in the downstream. Four GLOF hazard classes were derived according to glacial lake outburst potential and a flow magnitude assessment matrix, in which 11 glacial lakes were identified to have very high hazard and 24 to have high hazard. The GLOF hazard in BKB increased after the earthquake due to landslide deposits, which increased by 216.03 × 106 m3, and provides abundant deposits for outburst floods to evolve into debris flows. We suggest that in regional GLOF hazard assessment, small glacial lakes should not be overlooked for landslide deposit entrainment along a flood route that would increase the peak discharge, especially in earthquake-affected areas where large numbers of landslides were triggered.

On April 20, 2017, a flood from the Barun River, Makalu-Barun National Park, eastern Nepal formed a 2–3-km-long lake at its confluence with the Arun River as a result of blockage by debris. Although the lake drained spontaneously the next day, it caused nationwide concern and triggered emergency responses. We identified the primary flood trigger as a massive rockfall from the northwest face of Saldim Peak (6388 m) which fell approximately 570 m down to the unnamed glacier above Langmale glacial lake, causing a massive dust cloud and hurricane-force winds. The impact also precipitated an avalanche, carrying blocks of rock and ice up to 5 m in diameter that plummeted a further 630 m down into Langmale glacial lake, triggering a glacial lake outburst flood (GLOF). The flood carved steep canyons, scoured the river’s riparian zone free of vegetation, and deposited sediment, debris, and boulders throughout much of the river channel from the settlement of Langmale to the settlement of Yangle Kharka about 6.5 km downstream. Peak discharge was estimated at 4400 ± 1800 m3 s−1, and total flood volume was estimated at 1.3 × 106 m3 of water. This study highlights the importance of conducting integrated field studies of recent catastrophic events as soon as possible after they occur, in order to best understand the complexity of their triggering mechanisms, resultant impacts, and risk reduction management options.

The Bolivian Andes have experienced sustained and widespread glacier mass loss in recent decades. Glacier recession has been accompanied by the development of proglacial lakes, which pose a glacial lake outburst flood (GLOF) risk to downstream communities and infrastructure. Previous research has identified three potentially dangerous glacial lakes in the Bolivian Andes, but no attempt has yet been made to model GLOF inundation downstream from these lakes. We generated 2-m resolution DEMs from stereo and tri-stereo SPOT 6/7 satellite images to drive a hydrodynamic model of GLOF flow (HEC-RAS 5.0.3). The model was tested against field observations of a 2009 GLOF from Keara, in the Cordillera Apolobamba, and was shown to reproduce realistic flood depths and inundation. The model was then used to model GLOFs from Pelechuco lake (Cordillera Apolobamba) and Laguna Arkhata and Laguna Glaciar (Cordillera Real). In total, six villages could be affected by GLOFs if all three lakes burst. For sensitivity analysis, we ran the model for three scenarios (pessimistic, intermediate, optimistic), which give a range of ~ 1100 to ~ 2200 people affected by flooding; between ~ 800 and ~ 2100 people could be exposed to floods with a flow depth ≥ 2 m, which could be life threatening and cause a significant damage to infrastructure. We suggest that Laguna Arkhata and Pelechuco lake represent the greatest risk due to the higher numbers of people who live in the potential flow paths, and hence, these two glacial lakes should be a priority for risk managers.

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.

The Himalayas of South Asia are home to many glaciers that are retreating due to climate change and causing the formation of large glacial lakes in their absence. These lakes are held in place by naturally deposited moraine dams that are potentially unstable. Specifically, an impulse wave generated by an avalanche or landslide entering the lake can destabilize the moraine dam, thereby causing a catastrophic failure of the moraine and a glacial lake outburst flood (GLOF). Imja-Lhotse Shar Glacier is amongst the glaciers experiencing the highest rate of mass loss in the Mount Everest region, in part due to the expansion of Imja Tsho. A GLOF from this lake may have the potential to cause catastrophic damage to downstream villages, threatening both property and human life, which prompted the Nepali government to construct outlet works to lower the lake level. Therefore, it is essential to understand the processes that could trigger a flood and quantify the potential downstream impacts. The avalanche-induced GLOF process chain was modeled using the output of one component of the chain as input to the next. First, the volume and momentum of various avalanches entering the lake were calculated using Rapid Mass Movement Simulation (RAMMS). Next, the avalanche-induced waves were simulated using the Basic Simulation Environment for Computation of Environmental Flow and Natural Hazard Simulation (BASEMENT) model and validated with empirical equations to ensure the proper transfer of momentum from the avalanche to the lake. With BASEMENT, the ensuing moraine erosion and downstream flooding was modeled, which was used to generate hazard maps downstream. Moraine erosion was calculated for two geomorphologic models: one site-specific using field data and another worst-case based on past literature that is applicable to lakes in the greater region. Neither case resulted in flooding outside the river channel at downstream villages. The worst-case model resulted in some moraine erosion and increased channelization of the lake outlet, which yielded greater discharge downstream but no catastrophic collapse. The site-specific model generated similar results, but with very little erosion and a smaller downstream discharge. These results indicated that Imja Tsho is unlikely to produce a catastrophic GLOF due to an avalanche in the near future, although some hazard exists within the downstream river channel, necessitating continued monitoring of the lake. Furthermore, these models were designed for ease and flexibility such that local or national agency staff with reasonable training can apply them to model the GLOF process chain for other lakes in the region.

Proglacial braided river systems discharge large volumes of meltwater from ice sheets and transport coarse-grained sediments from the glaciated areas to the oceans. Here, we test the hypothesis if high-energy hydrological events can leave distinctive signatures in the sedimentary record of braided river systems. We characterize the morphology and infer a mode of formation of a 25 km long and 1–3 km wide Early Pleistocene incised valley recently imaged in 3-D seismic data in the Hoop area, SW Barents Sea. The fluvial system, named Bjørnelva River Valley, carved 20 m deep channels into Lower Cretaceous bedrock at a glacial paleo-surface and deposited 28 channel bars along a paleo-slope gradient of ~0.64 m km−1. The landform morphologies and position relative to the paleo-surface support that Bjørnelva River Valley was formed in the proglacial domain of the Barents Sea Ice Sheet. Based on valley width and valley depth, we suggest that Bjørnelva River Valley represents a braided river system fed by violent outburst floods from a glacial lake, with estimated outburst discharges of ~160 000 m3 s−1. The morphological configuration of Bjørnelva River Valley can inform geohazard assessments in areas at risk of outburst flooding today and is an analogue for landscapes evolving in areas currently covered by the Greenland and Antarctic ice sheets.