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Glacial lake outburst floods (GLOFs) are one of the major natural hazards in certain populated mountainous areas, e.g. the Himalayan region, which may lead to catastrophic consequences including fatalities. Evaluating the potential socio-economic impact of GLOFs is essential for mitigating the risk of GLOFs and enhancing community resilience. Yet in most of the cases, the impact evaluation of potential GLOFs is confronted with limited data availability and inaccessibility to most of the glacial lakes in the high-altitude areas. This study aims to exploit recent advances in Earth Observation (EO), open-source data from different sources, and high-performance hydrodynamic modelling to innovate an approach for GLOF risk and impact assessment. GLOF scenarios of different glacier dam breach width and depth are designed according to high-resolution aerial imagery and terrain data acquired from unmanned aerial vehicle surveying. High-performance hydrodynamic model supported by open-source multi-resolution data from the latest EO technologies is used to simulate the flood hydrodynamics to provide spatial and temporal flood characteristics. Detailed information on communities and infrastructure systems is collected and processed from multiple sources including OpenStreetMap, Google Earth, and global data products to support impact analysis. The evaluation framework is applied to Tsho Rolpa glacial lake in Nepal, which has been identified as one of the potentially dangerous glacial lakes that may create GLOFs to threaten the downstream communities and infrastructure. According to the simulation results, the worst GLOF scenario can potentially inundate 27 villages, 583 buildings and 20.8 km2 of agricultural areas, and pose high risk to 1 airport, 1 hydro power plant, 3 bus stations, and 21 bridges. Additionally, the spatial and temporal flood simulation results, including water depth, flow velocity and flood arrival time may help identify impacted sites and objects, which would be valuable for the development of evacuation plans and early warning systems.

The Upper Indus Basin (UIB) is prone to Glacial Lake Outburst Floods (GLOFs). Physical monitoring of such a large area on regular basis is a challenging task especially when the temporal and spatial extent of the hazard is highly variable. The study has been conducted in the Shyok sub-basin of UIB, where there are several human settlements which are endangered due to the GLOF hazard. Sudden breaches in the unstable moraine dams adjoining receding glaciers may occur because of rapid and huge accumulation of turbulent water in the glacial lakes. The purpose of this study was to map the two potentially dangerous glacial lakes and simulate the associated hazard in the downward settlements using HEC-RAS in the GIS environment using Landsat 7 remote sensing data. The ASTER Digital Elevation Model (DEM) is utilized to detect flow accumulation of glacial hazard involving slope, elevation, and orientation of the mountain glaciers. The study results have revealed that settlements of the Shyok Basin are threatened by the GLOF hazard. Keeping in view the seasonal growth of the two potentially dangerous glacial lakes of the Shyok Basin, a low discharge of 100 m3/s from both lakes can affect 20%, whereas a moderate discharge of 300 m3/s and a high discharge of 500 m3/s, respectively, can impact 30% and 40% of the Barah village habitat. The results of the study can provide a platform for the establishment of an early warning and monitoring system to minimize the impact of future GLOFs.

Glacial lake outburst floods (GLOFs) are a natural hazard that affects a number of communities around the world. GLOFs affect a number of downstream communities directly in Alaska, with a variety o...

Kyagar glacier lake outburst floods (GLOFs) have long been a serious nature hazard in Yarkant river basins of the Chinese Karakoram, threatening more than one million people. Between 1810 and 2018, 34 Kyagar GLOF events have been recorded, of which 26 occurred from 1960 onwards and their occurrence frequency reaches at least three times in each decade. An early warning system established in 2011 has successfully predicted the Kyagar GLOF events in 2015, 2016, 2017 and 2018, which provides an important reference for the monitoring and risk pre-evaluation of the GLOFs in Karakoram.

Petrographic and geostatistical analysis of linear dune forms on the Hanford Site, south-central Washington, have resulted in data supporting reinterpretation of depositional environments from eolian to primary glaciofluvial with post-depositional eolian modification. Miocene basalt flows of the Columbia River Basalt Group form the bedrock across the region overlain by Pliocene fluvial deposits from the preglacial Columbia River. Between ~21,000 and 12,000 YBP, glacial outburst floods scoured eastern Washington forming the Channeled Scablands. In the Pasco Basin, floodwaters were ponded behind flow restrictions resulting in deposition of coarse-grained gravel and sand sheets capped by fine-grained cyclic Touchet beds in higher elevation peripheral canyons. Outflow of ponded water mobilized the upper few meters of sediment forming a series of giant current ripples or megaripples. Modification of the surfaces of the megaripples under the influence of the Holocene wind regime has produced an eolian surficial signature. Subsurface excavations in these dune forms revealed the primary glaciofluvial provenance. Sedimentologic and petrographic evidence supports a general winnowing of fine-grained sediments from west to east under the current wind regime and includes both quartz and heavy minerals. These processes have resulted in the formation of an active dune field along the western bank of the Columbia River that overlies flood deposits locally.

Glacial lake outburst floods (GLOFs) are common where highly dynamic temperate glaciers exist, since seasonal changes in ice-conduit dynamics can start rapid lake drainages. Lakes dammed by cold-based glaciers, however, are less common and GLOFs from these glaciers have been rarely reported. Understanding both the origin and the failure mechanisms of lakes dammed by cold-based glaciers and subsequent flood processes is essential for territorial planning. We study a remarkable GLOF triggered by the failure of a subglacial lake in the Manflas Valley, Arid Andes of Chile, in 1985 providing insights into the lake’s origin, clarifying the failure mechanism and modelling the GLOF event-related dynamics. To identify the factors that contributed to the lake formation and failure, we analysed remotely sensed images, meteorological and topographic data. The GLOF dynamics were reconstructed using empirical (LAHARZ and MSF) and physical models (RAMMS). The obtained results were compared with field data of flow extent, depth and velocity. We show that the failed lake (4 × 106 m3) formed in a low-slope (≤ 10°) area and that extreme (≥ 90th percentile) annual precipitation before the GLOF contributed to the lake filling and probably to the dam collapse. The lake likely drained rapidly after mechanical failure of the ice-dam producing a high energy sediment-laden flow. We show the challenges of modelling large flows over long distances (dozens of kilometres) especially when flows change between Newtonian and Non-Newtonian phases. A GLOF can still endanger the Manflas Valley since a remnant of the lake of about 220.000 m3 exists and economic assets are located along the1985 GLOF path.

The frequency of glacier lake outbursts floods (GLOFs) is likely to increase with the ongoing glacier retreat, which produces new glacial lakes and enlarges existing ones. Here, we simulate the outburst of a potentially dangerous glacial lake in Bhutan by applying hydrodynamic modelling. Although the lake volume is known, several parameters connected to the dam breach and the routing of the flood are rough estimates or assumptions, which introduce uncertainties in the results. For this reason, we create an ensemble of nine outburst scenarios. The simulation of magnitude and timing of possible inundation depths is an important asset to prepare emergency action plans. For our case study in the Mo Chu River Basin, the results show that, even under the worst case scenario, little damage to residential buildings can be expected. However, such an outburst flood would probably destroy infrastructure and farmland and might even affect the operation of a hydroelectric powerplant more than 120 km downstream the lake. Our simulation efforts revealed that, by using a 30-m elevation model instead of a 5-m raster, flood magnitude and inundation areas are overestimated significantly, which highly suggests the use of high-resolution terrain data. These results may be a valuable input for risk mitigation efforts.

High-risk areas for glacial lake outburst flood (GLOF) disasters in China are mainly concentrated in the middle-eastern Himalayas and Nyainqêntanglha (Nyenchen Tanglha Mountains), Tibetan Plateau. In the past 20 years, glaciers in these regions have retreated and thinned rapidly as a response to regional climate warming, leading to the formation of new glacial lakes and the expansion of existing glacial lakes. These areas are located in the border belt between the Indian and the Eurasian plates, where tectonic seismic activity is also frequent and intense. Earthquakes have often compromised the stability of mountain slopes, glaciers, and moraine dams, resulting in an imbalance in the state of glacial lakes and an increase of loose materials in valleys. It is foreseeable that the possibility of GLOFs and disaster occurrence will be great in the context of frequent earthquakes and continued climate warming. This article presents the temporal and spatial characteristics of GLOF disasters, as well as the conditions and mechanisms of GLOF disaster formation, and proposes an integrated risk management strategy to cope with GLOF disasters. It aims to facilitate the mitigation of the impacts of GLOF disasters on mountain economic and social systems, and improve disaster risk analysis, as well as the capability of risk management and disaster prevention and reduction.

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.

Among the widespread phenomenon of outburst floods, a luckily unique event was the one artificially triggered by a bombardment during World War II. Among other reservoirs, the British Royal Air Force bombed the Mohne Reservoir located in the headwaters of the River Ruhr to interrupt drinking water supply for the Ruhr District, the armoury of Germany in those days. By this operation “Chastise”, the dam wall of the Mohne Reservoir was destroyed. Based on analysis of historical documents, eyewitnesses reports and flood marks along the pathway of the outburst flood its frontal wave velocity and flood levels are reconstructed. Based on the flood levels, the peak discharge in different sections along the valley of the River Ruhr could be modelled. As mentioned in the historic reports, the outburst flood could be significantly buffered in lakes long valley. By these measures, the peak discharge was significantly reduced and further damage avoided. The release of water from the lakes downstream of the destroyed dam wall confused flood chronologies in previous publications. The findings presented here are based on discussions of plausibility and consistency of the historic records and reports and could consider previously not known unpublished historic gauge data including newly modelled discharge estimations.

The modelling results of outburst floods and debris flows, which can possibly occur in the Daraisit River Valley, are presented in this paper. The modelling was carried out according to 2 scenarios: the outburst of Lake Sist, the formation of a debris flow on a large tributary of the Daraisist River. The FLO-2D hydrodynamic model and the modernized transport-shear mudflow model developed by Yu.B. Vinogradov were applied in this study. The evaluation of the outburst flood discharge was carried out on the basis of a bathymetric survey. A digital elevation model (DEM) ALOS PALSAR with a resolution of 12.5 m was used as relief data for the valley, and survey data from an unmanned aerial vehicle (UAV) was applied for the debris flow fan. As a result, maps of the spatial distribution of velocities and depths for the rivers Daraisist and Pyanj were obtained. The most vulnerable areas within the Sist village were also identified.

Remote seismic observations of a glacial lake outburst flood highlight potential for improving early warning systems., Glacial lake outburst floods (GLOFs) are a substantial hazard for downstream communities in vulnerable regions, yet unpredictable triggers and remote source locations make GLOF dynamics difficult to measure and quantify. Here, we revisit a destructive GLOF that occurred in Bhutan in 1994 and apply cross-correlation–based seismic analyses to track the evolution of the GLOF remotely (~100 kilometers from the source region). We use the seismic observations along with eyewitness reports and a downstream gauge station to constrain a numerical flood model and then assess geomorphic change and current state of the unstable lakes via satellite imagery. Coherent seismic energy is evident from 1 to 5 hertz beginning approximately 5 hours before the flood impacted Punakha village, which originated at the source lake and advanced down the valley during the GLOF duration. Our analysis highlights potential benefits of using real-time seismic monitoring to improve early warning systems.

In the spring of 1818, ice avalanches from the Giétro Glacier created an ice dam, which in turn formed a glacial lake in the Drance Valley (Canton of Valais, Switzerland). Today, its maximum volume is estimated to have been 25×106 m3. Cantonal authorities commissioned an engineer named Ignaz Venetz to mitigate the risk of the ice dam's failure. He supervised the construction of a tunnel through which a large volume of water was drained as the lake rose (9×106 m3 according to his estimates and 11×106 m3 according to our model). After 2.5 days of slow drainage, the ice dam failed on 16 June 1818 and caused major flooding in the Drance Valley up to 40 km downstream, resulting in about 40 deaths. Venetz's lake monitoring notes, numerous testimonies gathered in the disaster's aftermath, and our field survey have made it possible to collect a wealth of information on this event, which is one of the world's major documented glacial lake outburst floods. Reconstructing major outburst floods remains challenging because not only do they involve enormous volumes of water spreading over long distances but they are also associated with additional physical processes such as massive erosion; intense transport of ice, sediment, and debris; and damage to vegetation and buildings. This paper attempts to reconstruct the 1818 Giétro flood by focusing on its water component. We develop a simple model to estimate the initial hydrograph during the slow drainage and failure phases. The flood's features are deduced by solving the shallow‐water equations numerically. The computational framework involves six free parameters, of which five are constrained by physical considerations. Using iterative manual parameter adjustments, we matched the numerical simulations to the historical data. We found that the peak discharge was close to 14,500 m3/s, the flood's front velocity was about 6 m/s, and flow depth varied considerably along the River Drance's bed (from 30 m just downstream of the ice dam to 2 m on the alluvial fan, 24 km west of the dam). To achieve a good agreement between computations and historical data, we had to select a high value for the Manning friction coefficient n (with n as large as 0.08 s/m1/3). As the Drance Valley is narrow, high flow resistance caused the flood's leading edge to behave like a plug, moving at a fairly constant velocity, with little dependence on what happened behind it. This result may explain why a simple flood routing model is able to reproduce the flood's features, because in an Alpine valley, a lateral spreading of the water volume is limited., Water Resources Research, 55 (11), ISSN:0043-1397, ISSN:1944-7973

Climatic change-induced glacier recession has been accompanied by formation and growth of proglacial lakes in the Himalayan region, which pose an emerging significant threat to the downstream communities/settlements in the form of outburst floods. To understand spatiotemporal evolution patterns, sources and driving mechanism of formation and expansion of glacial lakes, a temporal inventory of glacial lakes (area > 2000 m(2)) in Chandra basin has been developed from 2000 to 2014 using IRS LISS-III images. From 2000 to 2014, the total number of glacial lakes in Chandra basin increased from 28 to 46 and area expanded from 1.91 +/- 0.24 km(2) to 3.26 +/- 0.24 km(2). Glacier recession and increased glacier melt runoff due to climate warming led to the formation and expansion of glacial lakes in space vacated by glacier recession. The increase in number and area of ice-dammed lakes at higher elevations confirms the continued glacier retreat in the basin. Lakes in contact or in the proximity of the mother glacier exhibit higher growth and formation rate. The accelerated growth of glacial lakes has resulted in increased hazard and damage potential of glacial lake outburst floods in Chandra basin. Seven potentially dangerous lakes are identified and analysed qualitatively for outburst probability.

The Teesta basin in Sikkim Himalaya hosts numerous glacial lakes in the high altitude glacierized region, including one of the largest and the fastest-growing South Lhonak Lake. While these lakes are mainly located in remote and unsettled mountain valleys, far-reaching glacial lake outburst floods (GLOFs) may claim lives and damage assets up to tens of kilometers downstream. Therefore, evaluating GLOF hazard associated with current and potential future glacier-retreat-driven changes is of high importance. In this work, we assess the future GLOF hazard of the South Lhonak Lake by integrating glacier and hydrodynamic modeling to calculate the lake's future volume and hydraulic GLOF characteristics and impacts along the valley. We identify the increased susceptibility of the lake to potential avalanche impacts as the lake grows in the future. Here we model six avalanche scenarios of varying magnitudes to evaluate the impact-wave generated in the lake and overtopping flow at the dam. Avalanche simulations indicate that the frontal moraine is susceptible to overtopping. The overtopping flow hydraulics is evaluated along the channel assuming no erosion of the moraine. Further, we consider three lake-breach scenarios to model GLOFs originating from the lake, flow propagation, and its downstream impacts. The uncertainty in the breach parameters including breach width and time of failure are calculated to estimate the upper and the lower hydraulic limits of potential future GLOF events. Further, the uncertainty in the flow hydraulics was evaluated using dynamic flood routing of six GLOFs that originate from the lake. Hydrodynamic GLOF modeling resulted in a predicted peak discharge of 4311 m3s−1, 8000 m3s−1, and 12,487 m3s−1 for breach depths of 20 m, 30 m, and 40 m respectively. The large-potential scenario suggests that maximum flow depth and flow velocity at Chungthang, a town proximally located to a major hydropower station built-in 2015, could reach up to 25–30 m and 6–9 m s−1, respectively. Mapping infrastructure exposed to GLOFs in the Teesta valley shows that many settlements and assets located along the river channel at Chungthang are potentially exposed to future GLOFs, indicating the need to conduct a full environmental impact assessment and potentially undertake GLOF risk mitigation measures.

All around the world, ancient legends exist about the Great Flood, and the influence of the Great Flood in human evolutionary history is a hotly debated topic. In China, the legend of the prehistoric Great Flood and Yu the Great’s flood control has a long history and is considered to be closely linked to the establishment of the Xia Dynasty. However, there is a lack of solid scientific evidence. Against this issue, some scholars have proposed that an earthquake around 1920 BCE in the Guanting Basin along the upper reaches of the Yellow River led to the creation of a lake by damming in the Jishi Gorge and that the outburst of water from that lake led to the massive flood in the Yellow River region. These studies provided new scientific evidence for the Chinese legend. In this paper, we date skeletal samples embedded in earthquake sand blasting from the Lajia site, analyze remains from natural disasters (such as earthquakes and floods) and also archaeological remains. In addition, we compared the skeletal samples dating with that of sediments from the dammed-up lake. Our results are inconsistent with those of previous scholars. The earthquake at the Lajia site occurred no earlier than 1800 BCE, and the dammed-up lake in Jishi Gorge had disappeared by 3600 BCE. Thus, the formation and outburst of the dammed lake, the sudden death of ancient humans at the Lajia site and the ancient earthquake were independent events occurring at different times. In addition, the massive flood in the upper reaches of the Yellow River did not actually happen. Thus, we argue against and invalidate the hypothesis that the massive flood was related to Yu the Great’s flood control and the establishment of the Xia Dynasty.

A super large rock avalanche occurred along Zhamu Creek, southeast Tibet on April 9, 2000, and triggered the Yigong landslide dam. The dam with a height of 60 m, a length of 2500 m, a width of 2500 m and a lake volume of 2.015 Gm3, threatened life and property both downstream and upstream. This paper reports a rapid assessment method for dam breaching with limited geometric and hydrological information of landslide dams. The method can be divided into three steps: first, Google map was used to obtain regional DEM data; second, Global Mapper was used to analyze the regional DEM data and obtain the river channel profiles; third, the HEC-RAS 4.1 was used to simulate the outburst discharge and flood evolution process. The results show that the excavation of spillway can decrease the dam breach peak discharge and control the life and property risk. The present method can be used for breach flood assessment of sudden unexpected landslide dams and providing a scientific basis for decision making in landslide dams risk management.

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 Glomsjo 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 m2 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 km2 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 14C dates we postulate an age of c. 10–10.4 cal ka BP for the Nedre Glomsjo drainage event and the contemporaneous margin of the ice sheet.

Unlike glaciers in other parts of the world, Karakoram glaciers seem to be stable or gaining in mass in response to global climate change, a phenomenon known as ‘the Karakoram anomaly’. Many of the glaciers experience irregular, frequent, and sudden advances (surges) that pose an increasing threat of ice dam lake formation and subsequent outburst flooding throughout the region. In this study, we document 179 glacial lake outburst floods (GLOFs) that occurred from 1533 to 2020 in five major valleys. Sixty-four of the events took place after 1970, and 37 of these had remote sensing imagery that covered the GLOF formation to breaching sequence. Thirty-six glaciers were associated with GLOFS due to ice-front advance building ice barriers in rivers. The Kayger and Khurdopin glaciers are the most hazardous examples, being responsible for 31.8% of major GLOFs in the entire Karakoram. Using a cross-correlation feature-tracking technique on remote sensing imagery, we analyzed ten surge glaciers and documented six surge events from 1990 to 2019. Results show periodic surge cycles for the Khurdopin, Kyager, Shishper, and Chilinji glaciers of c. 15–20 years, with a surge velocity in the mid-2010s higher than that of the late 1990s for all studied glaciers. The higher velocity of a glacier increases the risk of flooding downstream of the terminus because the transfer of a huge ice mass towards the terminus during the surge is a key factor for formation and reformation of series of ice-dammed lakes, thus determining the magnitude and frequency of outburst flood events. The response of Karakorum glaciers to global warming and climate forcing, comprising a continuum of glacier mass gain, ice thinning and ice advance, has resulted in lake formation and ice dam failures. We predict the frequency of GLOFs will increase in the future. These findings support the increasing anomalous behavior of glaciers in the Karakoram region. To synthesize the detailed observations, a conceptual model is presented of ice-dammed lake formation and GLOF initiation in response to glacier surging.

Glacial lake outburst floods (GLOF) are one of the most destructive natural disasters. Understanding GLOF evolution, and their impacts, plays a fundamental role in GLOF hazard assessment and risk management. Reconstructing historical GLOFs is an important exercise because detailed case studies of such glacial hazards are rare, which hinders the capacity of glacial hazard practitioners to learn from these events. In this study, we reconstruct a historical GLOF from moraine-dammed Chongbaxia Tsho (89.745°E, 28.211°N) in the Eastern Himalaya, which is a unique case study because the outburst flood cascaded into two further lakes downstream. We employ a combination of i) multi-source and multi-temporal satellite imagery, ii) field investigation (including an unmanned aerial vehicle survey), iii) numerical dam breach and hydrodynamic modelling and, iv) qualitative and quantitative cryospheric and meteorological analysis, to investigate the evolution of the GLOF hazard, simulate moraine dam failure and GLOF propagation, and explore the role that long- and short-term climate trends played in providing the conditioning factors for the outburst. Chongbaxia Tsho expanded rapidly between 1987 until 2001 in response to glacier recession most likely caused by a regional warming trend of +0.37 °C per decade. Based on satellite image analysis we refine the outburst date to be 6 August 2001, instead of 6 August 2000, as previously reported, and attribute an ice avalanche into the glacial lake originating from the receding parent glacier as the most likely trigger for moraine dam failure. Through DEM differencing and lake level decrease, we estimate that a total water volume of 27.1 ± 1.6 × 106 m3 was released from the lake during the event, and using dam breach modelling we estimate that the peak discharge at the breach was >6600 m3 s−1. The GLOF flowed through downstream Chongbamang Tsho and Chongbayong Tsho, both of which served to attenuate the GLOF and reduce downstream losses; the latter stored an estimated 96% of the flood volume. Precipitation totals in the weeks preceding the GLOF exceeded the historical mean by up to 40%, and may have contributed to instability of the parent glacier, and generation of an ice avalanche with enough impact energy to cause lake water to overtop the moraine dam and initiate breach development. A future GLOF from Chongbaxia Tsho cannot be ruled out, but more field data, including detailed lake bathymetry, and information pertaining to the sedimentological and geotechnical characteristics of the moraine dam, are required for a more robust parameterization of a predictive GLOF model and quantification of the hazard posed by a future GLOF.

Sedimentary characteristics of landslide dam outburst flood deposits are distinct from those of rainfall flood deposits due to their very high hydraulic energy and sediment concentration. While they have been studied well in geological record, investigations of modern outburst flood deposits are relatively rare. Well-preserved flood deposits and landforms caused by the June 2000 landslide dam outburst flood in the Yigong River, eastern Tibet provide an opportunity to evaluate such sedimentological response to a high energy modern event. The sedimentary characteristics of boulder bars and channel evolution over c. 17 km downstream of the breach were investigated by field survey and remote sensing interpretation. The results show that the post-flood channel migrated downstream and increased in curvature. The bar shape is very little changed toward downstream, but the bar area shows a fluctuating decrease. Poorly sorted accumulations composed of massive granular gravels and boulders near the breach indicate sediment-rich bedload depositing processes occurred during rapid rising stage flows. In contrast, there are eddy bars and deposition of fine gravel with horizontally bedded laminations 17 km downstream of the dam, suggesting suspended sediment dominated deposition with a rapid loss of transport capacity. Comparison with previous hydrodynamic simulations indicates that the rates of the rising stage and the falling stage strongly affect the sedimentary characteristics of boulder bars and slackwater deposits.

The presence of glacial lakes in the Himalaya makes it a potential mountain hazard, as catastrophic failure of such waterbodies may lead to high-magnitude glacial lake outburst flood (GLOF) events that can cause significant damage to the low-lying areas. The present study evaluates the hazard potential of the South Lhonak lake located in the state of Sikkim, using both one and two-dimensional hydrodynamic modeling approaches. Different breach parameters were calculated based on the lake bathymetry and moraine dimensions. The worst-case GLOF scenario is revealed during an overtopping failure of the moraine, producing a peak flood of 6064.6 m3 s−1 and releasing a total water volume of 25.7 × 106 m3. The GLOF hydrograph is routed to calculate peak flood (m3 s−1), inundation depth (m) and flow velocity (ms−1) along the main flow channel. The interaction of the flood wave with a major topographic obstruction located 15.6 km downstream of the lake, shows a significant reduction of the flow energy leading to a minimization of the South Lhonak GLOF impact. The flood wave reaches the nearest town Lachen, located at a distance of 46 km downstream from the lake, at 3 h 38 min after the initiation of the breach, with a peak flood of 3928.16 m3 s−1 and a maximum flow velocity of 13.6 ms−1. At Chungthang town, located at a distance of 62.35 km from South Lhonak lake, the flood wave potentially inundates settlements along the bank of the flow channel, where a peak flood of 3828.08 m3 s−1 is reached after 4 h of the initial dam breach event. The study also incorporates modeling of a framework to propose a potential flood remediation measure of the South Lhonak lake GLOF by demonstrating the effect of a lateral inline structure along the flow channel, to check the flow of the potential flood wave.

Funding to support this research from the University of St Andrews and the School of Geography and Sustainable Development is gratefully acknowledged. Continuous monitoring of glacial lakes, their parent glaciers and their surroundings is crucial because possible outbursts of these lakes pose a serious hazard to downstream areas. Ongoing climate change increases the risk of this hazard globally due to recession of glaciers leading to formation and expansion of glacial lakes, and permafrost degradation which impacts the stability of glaciers, slopes and moraines. Here, we demonstrate the capability of our approach for monitoring lake outburst susceptibility using time-series of Sentinel-1 Synthetic Aperture Radar (S-1 SAR) data. We selected Lunana in the Bhutanese Himalayas as an example region as it is highly susceptible to glacial lake outburst floods and suitable baseline data were available. We used Google Earth Engine (GEE) to calculate average radar backscatter intensity (ARBI) of glaciers, lakes, basins, and moraines. To determine the periodicity of the highest and the lowest radar backscatter intensity, we denoised the ARBI data using a Fast Fourier Transform and autocorrelated using a Pearson correlation function. Additionally, we determined glacier melt area, basin melt area, lake area, open water area, and lake ice area using radar backscatter intensity data. The Persistent Scatterer Interferometry (PSI) technique was used to investigate the stability of moraines and slopes around glacial lakes. The PSI results were qualitatively validated by comparison with high-resolution digital elevation model differencing results. Our approach showed that glaciers and basins in the region underwent seasonal and periodic changes in their radar backscatter intensity related to changes in ice and snow melt. Lakes also showed seasonal changes in their radar backscatter intensity related to the variation of lake ice and open water area, but the radar backscatter intensity change was not periodic. We could also infer lake area change using a time-series radar backscatter intensity data such as the rapid expansion of Bechung Tsho. The PSI analysis showed that all the terminal moraines were stable except Drukchung Tsho. Its terminal moraine showed subsidence at the rate of –5.18 mm/yr. Sidewalls of lakes were also stable with the exception of Lugge Tsho at site 4. Due to the free availability of S-1 SAR data, the efficiency of processing a large amount of imagery within GEE, and the PSI technique, we were able to understand the outburst susceptibility of glacial lakes in the region at great detail. The regular acquisition of S-1 SAR data enables continuous monitoring of glacial lakes. A similar approach and concept can be transferred to any geographic region on earth that shares similar challenges in glacial lake monitoring. Publisher PDF

Glacier lake outburst floods (GLOFs), especially those in the Arctic, can deliver exceptionally high volumes of sediment and solutes to fjords and shallow-marine settings, in comparison to typical seasonal river flows. These sediments and solutes strongly affect coastal geomorphology and aquatic ecosystems, yet are rarely observed. In this study, we have quantified the short-term geomorphological response of the most distal part of the Zackenberg River (northeast Greenland), where it enters Young Sund, to a glacier lake outburst flood that occurred on August 6th 2017. The main aims were to: (1) quantify riverbank and floodplain geomorphology changes that occurred as a consequence of the flood; (2) analyse the spatial patterns of those geomorphological changes and suggest the key controls on them. We used a time-series of very high-resolution UAV-generated images taken on the 5th, 6th, and 8th of August 2017, which enabled us to compare pre- and post-flood fluvial geomorphology. The GLOF induced intense and widespread geomorphological changes, which was surprising because several floods of a similar magnitude have occurred along this river. Approximately 30% of the area of interest experienced changes that were larger than the minimum level of detection (0.15 m). Lateral erosion reached almost 10 m in some places. The total volume loss from bank erosion was at least 26,561 m3 (+/− 14%), whereas the deposition was at least 7745 m3 (+/− 39%). Such an intensive geomorphological response resulted from a combination of factors; namely: (1) bank geometry; (2) composition of bank material; (3) time of occurrence of the event; (4) presence of permafrost; (6) channel geometry; and (7) multitude and diversity of geomorphological processes. We speculate the severity of the geomorphological impact relative to that from previous floods could have been due to warming air temperatures that provided sediment from thawed permafrost, and to an aggrading delta that raised the river base level. Overall, we contend that climate warming will not only make outburst floods from glaciers more likely but that those floods will achieve more geomorphological work with mechanical erosion of permafrost. Erosion and gravitational failures during future flood events will perhaps become even more widespread and intense.

Filiación institucional de autor: Alejo Cochachín Rapre / Autoridad Nacional del Agua - Unidad de Glaciología y Recursos Hídricos (ANA-UGRH), Huaraz, Peru Original abstract: The Quillcay catchment in the Cordillera Blanca, Peru, contains several glacial lakes, including Lakes Palcacocha (with a volume of 17 x 106 m3), Tullparaju (12 x 106 m3) and Cuchillacocha (2 x 106 m3). In 1941 an outburst of Lake Palcacocha, in one of the deadliest historical glacial lake outburst floods (GLOF) worldwide, destroyed large parts of the city of Huaraz, located in the lowermost part of the catchment. Since this outburst, glaciers and glacial lakes in Quillcay catchment have undergone drastic changes, including a volume increase of Lake Palcacocha between around 1990 and 2010 by a factor of 34. In parallel, the population of Huaraz grew exponentially to more than 120,000 inhabitants nowadays, making a comprehensive assessment and mapping of GLOF hazards for the Quillcay catchment and the city of Huaraz indispensable. Here we present a scenario-based multi-source GLOF hazard mapping, applying a chain of interacting numerical models to simulate involved cascading mass movement processes. Susceptibility assessments for rock-ice avalanches and breach formation at moraine dams were used to define scenarios of different magnitudes and related probabilities, which are then simulated by corresponding mass movement models. The evaluation revealed, that (1) the three investigated lakes pose a significant GLOF hazard to the Quillcay Catchment and the city of Huaraz, (2) in some scenarios the highest hazard originates from the lake with the smallest volume (Cuchillacocha), and (3) current moraine characteristics of Lake Palcacocha cannot be compared to the situation prior and during the 1941 outburst. Results of outburst floods obtained by the RAMMS model were then converted into intensity maps and corresponding hazard levels according to national and international standards, and eventually combined into the GLOF hazard map for the entire Quillcay catchment, including the urban area of Huaraz. Besides technical aspects of such a multi-source model-based hazard mapping, special attention is also paid to approval and dissemination aspects in a complex institutional context. Finally, some general conclusions are drawn and recommendations are given, that go beyond the presented case of the Quillcay Catchment. Artículo en acceso abierto Realiza una evaluación y un mapeo exhaustivo de los peligros de inundación por desborde violento de lago glaciar (en inglés, Glacier lake outburst flood o GLOF) para la cuenca de Quillcay y la ciudad de Huaraz, zona que contiene varios lagos glaciares, incluidos los lagos Palcacocha (con un volumen de 17 x 106 m3), Tullparaju (12 x 106 m3) y Cuchillacocha (2 x 106 m3) y que sufriera una de las inundaciones más mortales e históricas del mundo en 1941. Además de los aspectos técnicos de amenazas basado en modelos de múltiples fuentes, este mapeo presta especial atención a los aspectos de aprobación y difusión en un contexto institucional complejo. Finalmente, extrae algunas conclusiones generales y brinda recomendaciones, que van más allá del caso presentado.

The 1988 glacial lake outburst flood (GLOF) in Guangxieco Lake is studied based on geomorphological evidence, interviews with local residents, field surveys in 1990 and 2007, and satellite images from different years. The findings are as follows. (1) The outburst event was caused by two major factors, namely, intense pre-precipitation and persistent high temperatures before the outburst and the low self-stability of the terminal moraine dam as a result of perennial piping. (2) The GLOF, with the peak discharge rate of 1270 m3 s−1, evolved along Midui Valley in the following order: sediment-laden flow, viscous debris flow, non-viscous debris flow, and sediment-laden flood, which was eventually blocked by Palongzangbu River. (3) A comparison between the conditions during the outburst in 1988 and the present conditions suggests a small possibility of a future outburst unless drastic changes occur in landscape and climate. Reconstructing the outburst conditions and the GLOF processes is helpful in assessing a potential outburst in glacier lakes in Tibet.

In April 2000 a large-scale rock avalanche dammed the Yigong Zangpo River, forming an extensive rockslide-dammed lake. The impoundment lasted for 62 days before a catastrophic breaching caused a massive outburst flood in the Yarlung Zangpo (Tibet) and the Dihang rivers (India) that travelled downstream to the main floodplain of the Brahmaputra in northeastern India. In response to discrepancies in the published literature on the event, we present a review and re-evaluation of the characteristics of the rock avalanche and associated landslide-dammed lake. We use digital topographical data (SRTM-3) and dynamic landslide modelling (DAN-W and DAN3D) to determine the salient characteristics of the damming landslide and to characterise its behaviour. Our analysis indicates that the volume of the damming rockslide was ca. 115 Mm3, including 91 Mm3 from the initial rockslope failure (bulked during disaggregation to 109 Mm3) and 6 Mm3 from entrainment during its 10.1 km travel down Zhamulong gully. The debris travelled with an average velocity of 15–18 m/s and resulted in a landslide dam on the Yigong River with a minimum height of about 55 m. Using LANDSAT-7 imagery (obtained before, during, and after impoundment) in conjunction with an SRTM-3 DEM, we reproduced the filling of the lake. We determine that the landslide dam formed an extensive reservoir with an impounded volume of 2.015 Gm3 and a maximum possible lake level of 2264 m asl (rounded to 2265 m asl). Our figures differ from those previously published but are believed to be well-constrained verifiable estimates of the volumes of the 2000 Yigong events. The outburst occurred after an attempt by army personnel to manually dig a spillway over the landslide debris and resulted in the entire volume of the lake draining in about 12 h. The outburst flood travelled over 500 km south into India, with a recorded rise in river level of 5.5 m at the Pasighat gauging station, 462 km downstream. In terms of historical outburst volumes from rockslide-dammed lakes, the volume of the 2000 Yigong event is only exceeded by that of the 1841 outburst flood from the Indus River rockslide-dammed lake, northern Pakistan.

Glacial lake outburst floods (GLOFs) are a serious and potentially increasing threat to livelihoods and infrastructure in most high-mountain regions of the world. Here, we integrate modelling approaches that capture both current and future potential for GLOF triggering, quantification of affected downstream areas, and assessment of the underlying societal vulnerability to such climate-related disasters, to implement a first-order assessment of GLOF risk across the Himalayan state of Himachal Pradesh (HP), Northern India. The assessment thereby considers both current glacial lakes and modelled future lakes that are expected to form as glaciers retreat. Current hazard, vulnerability, and exposure indices are combined to reveal several risk ‘hotspots’, illustrating that significant GLOF risk may in some instances occur far downstream from the glaciated headwaters where the threats originate. In particular, trans-national GLOFs originating in the upper Satluj River Basin (China) are a threat to downstream areas of eastern HP. For the future deglaciated scenario, a significant increase in GLOF hazard levels is projected across most administrative units, as lakes expand or form closer towards steep headwalls from which impacts of falling ice and rock may trigger outburst events. For example, in the central area of Kullu, a 7-fold increase in the probability of GLOF triggering and a 3-fold increase in the downstream area affected by potential GLOF paths can be anticipated, leading to an overall increase in the assigned GLOF hazard level from ‘high’ to ‘very high’. In such instances, strengthening resilience and capacities to reduce the current GLOF risk will provide an important first step towards adapting to future challenges.

One of the consequences of recent glacier recession in the Cordillera Blanca, Peru, is the risk of glacial lake outburst floods (GLOFs) from lakes that have formed at the base of retreating glaciers. GLOFs are often triggered by avalanches falling into glacial lakes, initiating a chain of processes that may culminate in significant inundation and destruction downstream. This paper presents simulations of all of the processes involved in a potential GLOF originating from Lake Palcacocha, the source of a previously catastrophic GLOF on 13 December 1941, killing about 1800 people in the city of Huaraz, Peru. The chain of processes simulated here includes (1) avalanches above the lake; (2) lake dynamics resulting from the avalanche impact, including wave generation, propagation, and run-up across lakes; (3) terminal moraine overtopping and dynamic moraine erosion simulations to determine the possibility of breaching; (4) flood propagation along downstream valleys; and (5) inundation of populated areas. The results of each process feed into simulations of subsequent processes in the chain, finally resulting in estimates of inundation in the city of Huaraz. The results of the inundation simulations were converted into flood intensity and preliminary hazard maps (based on an intensity-likelihood matrix) that may be useful for city planning and regulation. Three avalanche events with volumes ranging from 0.5 to 3 × 106 m3 were simulated, and two scenarios of 15 and 30 m lake lowering were simulated to assess the potential of mitigating the hazard level in Huaraz. For all three avalanche events, three-dimensional hydrodynamic models show large waves generated in the lake from the impact resulting in overtopping of the damming moraine. Despite very high discharge rates (up to 63.4 × 103 m3 s−1), the erosion from the overtopping wave did not result in failure of the damming moraine when simulated with a hydro-morphodynamic model using excessively conservative soil characteristics that provide very little erosion resistance. With the current lake level, all three avalanche events result in inundation in Huaraz due to wave overtopping, and the resulting preliminary hazard map shows a total affected area of 2.01 km2, most of which is in the high hazard category. Lowering the lake has the potential to reduce the affected area by up to 35 %, resulting in a smaller portion of the inundated area in the high hazard category.

Glacial Lake Outburst Floods (GLOFs) constitute a major threat in glacierized regions. 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. GLOFs are particularly common in the Baker River watershed (Patagonia, 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 relationship between GLOF frequency 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 Neoglacial advances that are coeval with periods of lower temperature and increased precipitation. 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.

A great number of glacial lakes have appeared in many mountain regions across the world during the last half-century due to receding of glaciers and global warming. In the present study, glacial lake outburst flood (GLOF) risk assessment has been carried out in the Teesta river basin located in the Sikkim state of India. First, the study focuses on accurate mapping of the glaciers and glacial lakes using multispectral satellite images of Landsat and Indian Remote Sensing satellites. For glacier mapping, normalized difference snow index (NDSI) image and slope map of the area have been utilized. NDSI approach can identify glaciers covered with clean snow but debris-covered glaciers cannot be mapped using NDSI method alone. For the present study, slope map has been utilized along with the NDSI approach to delineate glaciers manually. Glacial lakes have been mapped by supervised maximum likelihood classification and normalized difference water index followed by manual editing afterwards using Google Earth images. Second, the first proper inventory of glacial lakes for Teesta basin has been compiled containing information of 143 glacial lakes. Third, analysis of these lakes has been carried out for identification of potentially dangerous lakes. Vulnerable lakes have been identified on the basis of parameters like surface area, position with respect to parent glacier, growth since 2009, slope, distance from the outlet of the basin, presence of supraglacial lakes, presence of other lakes in downstream, condition of moraine, condition of the terrain around them, etc. From these criterions, in total, 18 lakes have been identified as potentially dangerous glacial lakes. Out of these 18 lakes, further analysis has been carried out for the identification of the most vulnerable lake. Lake 140 comes out to be the most vulnerable for a GLOF event. Lastly, for this potentially dangerous lake, different dam break parameters have been generated using satellite data and digital elevation model. The volume and depth have been computed using empirical formulae, and other parameters such as cross-sections from the lake to outlet etc. have been prepared in ArcGIS 9.3. The GLOF which can be triggered by Lake 140 was modelled and simulated using MIKE-11 software's hydrodynamic module. As a result, flood values and hydrograph have been obtained. The flood at lake site comes out to be 2611.136 cumec which get mitigated to 1417.844 cumec at the outlet.

A flood that thundered through eastern Nepal in July 2016 left a telltale seismic signature and caused more erosion than local monsoon rains, new research shows.

The Chucchún River basin was hit by glacial lake outburst flood (GLOF) triggered by ice/rock avalanche which caused spill over from the Lake 513 (April 11, 2010). The whole region is also highly susceptible for landslide occurrences, therefore the GLOF and landslide multi-hazard map were prepared for the watershed. Definition of the GLOF hazard zones was done using 1D mathematical model HEC-RAS for modeling of flooded areas. Landslide hazard zonation was based on landslide inventory mapping and historical records of the landslide occurrences. Resulting multi-hazard map shows that 26% of the studied river basin is under some degree of hazard from landslides or GLOFs. It clearly shows the most endangered inhabited areas as well as places, where floods and landslides may adversely affect each other increasing intensity of the hazardous event. Nebezpečí vzniku povodní z ledovcových jezer a sesuvů v povodí řeky Chucchún, Cordillera Blanca, Peru Pohoří Cordillera Blanca leží ve středním Peru a je součástí kontinentálního rozvodí mezi Atlantským a Tichým oceánem. Pohoří je budováno převážně granodiority a tonality třetihorního stáří, které na jeho úpatí v údolí řeky Santy přecházejí do druhohorních sedimentárních a vulkanických hornin. Ty bývají často překryty čtvrtohorními glaciálními a fluvioglaciálními sedimenty. Pohoří je na západě vymezeno výrazným normálovým zlomem. Studované povodí řeky Chucchún je pravým přítokem řeky Santy. V jeho horní části se nacházejí ledovce a tři ledovcová jezera. V roce 2010 se pod vrcholem Hualcán (6125 m n. m.) uvolnila lavina ledu a sněhu, která zasáhla jezero 513. Došlo k přelití vody přes skalní práh tvořící hráz a vznikla povodeň, která zničila několik domů a mostů v údolí. Tato relativně malá povodeň vyvolala velké obavy místních obyvatel, a proto byly zahájeny práce k vytvoření mapy nebezpečí pro možné budoucí povodně. Vzhledem k tomu, že pohoří Cordillera Blanca i údolí řeky Santy jsou silně náchylné ke vzniku různých forem svahových pohybů, byla vytvořena také mapa nebezpečí pro tyto jevy. Mapa nebezpečí pro povodně je vytvořena na základě modelování rozlivů povodní s různým maximálním průtokem. Výpočty byly provedeny v programu HEC-RAS na základě topografických profilů zaměřených přímo v terénu. Vzhledem k velmi omezeným historickým informacím o vzniku povodní z ledovcových jezer, byly velikosti povodní stanoveny na základě události z roku 2010. Během této povodně byl modelovaný maximální průtok 580 m3 s−1. Předpokládáme, že povodně podobné velikosti jsou v daném území nejčastější. Proto rozliv této povodně definuje vysoký hazard. Povodeň dosahující maximální úrovně hladiny o 1 m vyšší než povodeň z roku 2010 a s průtokem 965 m3 s−1 definuje oblast středního nebezpečí z povodní. Mapa nebezpečí vzniku sesuvů byla vytvořena na základě inventarizace sesuvů s pomocí dostupných snímků GoogleEarth s vysokým rozlišením. K vymapovaným svahovým deformacím byly na základě zkušeností ze studované oblasti a morfologických poměrů, dokresleny oblasti předpokládaného nejzazšího dosahu jednotlivých svahových deformací. Nejvyšší stupeň nebezpečí byl přiřazen k přívalovým proudům, které v širší studované oblasti vznikají nejčastěji. Střední nebezpečí bylo přiděleno k sesuvům a nejmenší nebezpečí představují hluboké svahové deformace. Mapy nebezpečí vzniku sesuvů a povodní byly zkombinovány, aby daly lepší přehled o přírodních nebezpečích ve studovaném povodí.

Kedarnath (3,533 m, 30°44′05″N, 79°04′02″E) is situated within a kilometre of the termini of the Chorabari and Companion glaciers in the Indian Himalaya. An outburst flood from a lake (3,845 m) formed by right lateral moraine of the former caused severe damage to the village on 17 June 2013. We determined various physical parameters of the lake from three digital elevation datasets (CartoDEM, SRTM and ASTER) and selected the SRTM-derived data as they appeared to portray the region more accurately. The obtained parameters were used in predictive equations suggested by different authors to estimate peak discharge of the flood. We also compared high-resolution images of 10 December 1965 (Corona), June 2011 (Bing) and 25 June 2013 (Catrosat-1 Pan + LISS-4mx) to assess the damage caused to the village besides other geomorphic changes. The results showed that at least 149 mm of rainfall in its 291-ha catchment was required to fill up the lake, without considering the presence of antecedent water and loss from seepage and evaporation. At the point of breaching, the lake released 0.43 × 106 m3 of water with a peak discharge of 1,352 cumecs. The north-western section of Kedarnath village was on the direct path of the debris flow triggered by the flood and was almost completely destroyed. The southern and south-eastern sections were least affected. Out of 37,299 m2 of pre-event roof area of Kedarnath (259 structures), 44.2 % were obliterated and 26.7 % were partly damaged, representing 138 and 56 structures, respectively. Only one-quarter of the structures of the village emerged intact or slightly affected after the event.

Climate change has led to the formation of numerous high-altitude lakes of glacial origin in the Himalaya. Safed Lake is one of the largest glacial lakes, located at an elevation 4882 m a.s.l. in the state of Uttarakhand, central Himalaya, India. A temporal analysis of the lake surface using satellite imagery shows that the lake has grown more than double its size from 0.10 km2 to 0.23 km2 over the past 50 years. In this study, we performed a hazard assessment of the lake using 1D and 2D hydrodynamic modeling. We identified the potential glacial lake outburst flood (GLOF) triggering factors and evaluated the impact of a moraine breach event of the lake on the nearest village located 16.2 km downstream of the lake. A series of dynamic simulations were performed for different scenario-models based on varied breach depths, breach widths and time of moraine failure. In a worst-case GLOF scenario where breach depth reached up to 60 m, hydrodynamic routing of the breach hydrograph along the given channel revealed inundation depth up to 5 m and flow velocities up to 3.2 m s&minus, 1 at Milam village. Considering the flat geometry of the frontal moraine, hazard assessment of the lake was performed by for different breach incision depths (30 and 15 m). In addition, the study incorporated a series of hydrodynamic routing to understand the sensitivity of GLOF to different model input parameters and terrain conditions. The sensitivity of the initial GLOF hydrograph to breach formation time (Tf) was evaluated by considering different hypothetical breach scenarios with a varied time of failure. Increases of 11.5% and 22% in the peak flooding were recorded when the moraine failure time was decreased by 15 and 30 min respectively. The two-dimensional sensitivity revealed flow velocity (m s&minus, 1) to be more sensitive to change in Manning&rsquo, s N when compared to the inundation depth (m). Changes of 10.7% and 0.5% in the mean flow velocity (in m s&minus, 1) and flow depth (in m) were recorded when dN was 0.01. The flow velocity was more sensitive to the slope and the top-width of the channel when compared to the inundation depths. A regression of flow velocity versus slope gives a correlation coefficient of 0.76. GLOF flow hydraulics are sensitive to changes in terrain elevation, where flow depth and velocity vary in a similar manner.

Floods from moraine-dammed lake failures can have long standing effects not only on riverine landscapes but also on mountain communities due to the high intensity (i.e. great depth and high velocities) and damaging capacity of glacial lake outburst floods (GLOFs). GLOFs may increase in frequency as glaciers retreat and new lakes develop and there is an urgent need to better understand GLOF dynamics and the measures required to reduce their negative outcomes. In Patagonia at least 16 moraine-dammed lakes have failed in historic time, however, data about GLOF dynamics and impacts in this region are limited. We reconstruct a GLOF that affected a small village in Chilean Patagonia in March 1977, by semi structured interviews, interpretation of satellite images and 2D hydraulic modelling. This provides insight into the GLOF dynamics and the planning issues that led to socioeconomic consequences, which included village relocation. Modelling shows that the water released by the GLOF was in the order of 12–13 × 106 m3 and the flood lasted for about 10 h, reaching a maximum depth of ~ 1.5 m in Bahia Murta Viejo, ~ 26 km from the failed lake. The lake had characteristics in common with failed lakes worldwide (e.g. the lake was in contact with a retreating glacier and was dammed by a narrow-steep moraine). The absence of land-use planning and the unawareness of the GLOF hazard contributed to the village flooding. The Rio Engano GLOF illustrates how small-scale and short-distance migration is a reasonable coping strategy in response to a natural hazard that may increase in frequency as atmospheric temperature rises and glaciers retreat.

We present geomorphological evidence of large, previously undocumented, early Holocene ice-dammed lakes in the Scandinavian Mountains of northwestern Sweden. The lakes extents indicate that the last remnants of the Scandinavian Ice Sheet were located east of the mountain range. Some early pioneering works have presented similar reconstructions, whereas more recently published reconstructions place the last ice remnants in the high mountains of Sarek. Using high-resolution airborne LiDAR data we have mapped a large number of hitherto undocumented shorelines in some of the main valleys within the northern Scandinavian mountain range. Our results indicate that a larger system of ice-dammed lakes existed in this region than previously thought. The lakes were dammed between the main water divide to the west and the retreating ice sheet margin to the east. The shorelines dip towards the northwest with gradients ranging from 0.5 to 0.4 m/km, from the oldest to the youngest. Further, we have compiled Lateglacial and Holocene shoreline data along the Norwegian coast and from within the Baltic Sea basin and reconstructed the isostatic uplift along a 1400 km long northwest-southeast transect from the Norwegian Sea to Lake Ladoga. By comparing the measured ice-dammed lake shoreline gradients to the dated marine shorelines, we infer that the lakes may have existed for several centuries following 10.2 cal ka BP. We also describe large deposits and extensive erosive features, which demonstrate that a catastrophic glacial lake outburst flood (GLOF) took place eastward along the Pite River Valley. Based on cross-cutting relations to raised shorelines developed in the early Holocene Ancylus Lake (Baltic Sea basin) we conclude that the flood and thus the final phase of deglaciation took place within the time interval 10.3–9.9 cal ka BP. publishedVersion

Natural glacier events such as ice avalanches, debris flows or glacier lake outburst floods (GLOF) may have hazardous impacts on the downstream area of the glacier and can cause severe destructions. The Inylchek Glaciers in Kyrgyzstan, are one of the largest non-polar glacier systems in the world. Each year, an ice-dammed lake is formed (Lake Merzbacher) by melt-water which drains predominantly every year suddenly within a few days causing a destructive flood. To understand the mechanism of the GLOF, a network of continuously operating GPS stations at the Inylchek Glaciers provide daily horizontal and vertical positions of the ice-dam in front of the Merzbacher Lake. Irrespective of the general motion during the year, the ice-dam is strongly influenced by the formation and outburst of the lake. Especially the vertical position and surface velocities increase shortly before the GLOF supporting the assumption that the ice-dam adjacent to the lake becomes afloat. After the GLOF, e.g. in 2014, the elevation decreases rapidly by 20 m within 8 days. In 2015, the GLOF changes in timing, magnitude and available lake water volume but the motion pattern of the ice-dam is similar compared to the year before. These comparable results have the potential to develop an early warning system for the glacier-dammed lake outburst flood.