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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.

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.

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.

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.

This study reports on geomorphic and sedimentary evidence for a gigantic breakout flood from Towada caldera, Honshu Island, northeast Japan, as observed along the Oirase River downstream from the outlet of the caldera lake. A number of features of the Oirase River are inconsistent with its present discharge, including the occurrence of 1) hanging valleys and a horseshoe-shaped waterfall in the upstream gorge area, 2) boulder bars and scattered flood boulders, 3) a dry valley at a high elevation in the gorge, and 4) a large fan (the Sanbongi fan) in the downstream area of the river. The Sanbongi fan is composed of thick, lithic-rich hyperconcentrated flow deposits that include pumice clasts derived from the 15 ka Towada–Hachinohe ignimbrite and well-rounded meter-sized (and outsized) boulders derived from bedrock of welded ignimbrite. The deposits are entirely aggradational, with no major channels, indicating the absence of a major hiatus during sedimentation. The depositional facies also indicate that a single sheet-like flood event deposited the sediment within the Sanbongi fan area. Based on the age of the Sanbongi fan, the flood occurred between 15 and 12 ka, after eruption of the Towada–Hachinohe ignimbrite. The most probable water source for the flood is Towada caldera lake, as suggested by landforms and sediments along the lake outlet. A paleohydrological analysis indicates that at least 6 km 3 of water was released from the caldera at a peak discharge of > 2 × 10 4 to 3 × 10 5 m 3 s − 1 during the breakout flood. Although the Sanbongi fan was previously considered to be a “normal” alluvial fan that formed during a stage of low-stand sea level, the present results show that the formation of the fan was closely related to a catastrophic flood from Towada caldera rather than perennial fluvial activity, climate change, or a change in relative sea level.

Landslide damming of valleys may have a significant effect on the evolution of fluvial landscapes. The southeastern Tibetan Plateau is highly prone to landslide damming due to its deeply incised valleys and young, active geology. Here we present a sedimentological investigation of a landslide-dammed lake in the upper reach of Lulang River on the eastern Himalayan syntaxis. Detailed interpretation of lacustrine varve, lakeshore, and subaqueous delta sediment shows that Lulang landslide-dammed lake (LLDL) had a surface elevation of 3360 m a.s.l., an area of 33 x 10(6) m(2), and a volume of 6.5 x 10(2) m(3). Radiocarbon dating of six organic clay lacustrine samples demonstrate that LLDL formed before 24.2 ka cal. BP and persisted for at least 8.8 ka. Sediment infill reached full capacity soon after 15.4 ka cal. BP and fluvial conditions then prevailed. Sedimentary evidence and morphological analysis of cross sections along the LLDL outlet channel revealed a larger, earlier lake with a total volume of 4.3 x 10(9) m(3) and water surface elevation at 3570 m a.s.l. that failed catastrophically; the resulting outburst flood drained 98.5% of the impounded lake. The remnant lake maintained a relatively stable water level of 3360 m a.s.l. for its lifetime of at least 8.8 ka. Long profile and steepness index analysis indicate that the location of the catastrophic dam failure and subsequent long-term blockage is associated with a knickpoint. The origin of the knickpoint may have been polygenetic, however, the landslide damming seems to have increased its distinctiveness and persistence. The relatively wide valley and low channel slope characteristic of reaches upstream of LLDL is likely to have resulted from glacial activity, rather than backwater aggradation which had only a local influence. (C) 2019 Elsevier B.V. All rights reserved.

Unusual channel-amphitheatre landforms are present in Late Pleistocene–early Holocene, subaqueous fan and delta deposits in the glacial Lake Fraser basin, central British Columbia. The lake formed during the decay of the last Cordilleran Ice Sheet and drained ~11,500 years ago during a large outburst flood. The fronts of a delta and two subaqueous fans consisting of silt to fine sand are marked by branching networks of wide, nearly flat channels that terminate upstream in digitate, steep-walled amphitheatres. We propose that these channel-amphitheatre landforms formed by liquefaction flowslides that were induced by the rapid drawdown of glacial Lake Fraser during the outburst flood. Similar geomorphic forms, which we believe also to be associated with rapid drawdowns of large Late Pleistocene–early Holocene lakes, occur elsewhere in North America. A recent tailings dam failure and an intentional breaching of a 100-year-old hydroelectric dam provide insights into the processes responsible for the landforms. By using geomechanical analysis, we show how rapid lake drawdown can trigger liquefaction flowslides in deposits of silt to fine sand. The novelty of our approach lies in combining geomechanical reasoning with geomorphic analogues to understand histories of ancient glacier-dammed lakes and of the glacial lake outburst floods that are sourced from them.

High resolution digital terrain models (DTMs) generated from airborne LiDAR data and supplemented by field evidence are used to map glacial landform assemblages dating from the last glaciation (Midlandian glaciation; OI stages 2–3) in the central Irish Midlands. The DTMs reveal previously unrecognised low-amplitude landforms, including crevasse-squeeze ridges and mega-scale glacial lineations overprinted by conduit fills leading to ice-marginal subaqueous deposits. We interpret this landform assemblage as evidence for surging behaviour during ice recession. The data indicate that two separate phases of accelerated ice flow were followed by ice sheet stagnation during overall deglaciation. The second surge event was followed by a subglacial outburst flood, forming an intricate esker and crevasse-fill network. The data provide the first clear evidence that ice flow direction was eastward along the eastern watershed of the Shannon River basin, at odds with previous models, and raise the possibility that an ice stream existed in this area. Our work demonstrates the potential for airborne LiDAR surveys to produce detailed paleoglaciological reconstructions and to enhance our understanding of complex palaeo-ice sheet dynamics.

Glacial lake outburst floods (GLOFs) have recently become one of the primary natural hazards in the Himalayas. There is therefore an urgent need to assess GLOF hazards in the region. Cirenmaco, a moraine-dammed lake located in the upstream portion of Zhangzangbo valley, Central Himalayas, has received public attention after its damaging 1981 outburst flood. Here, by combining remote sensing methods, bathymetric survey and 2D hydraulic modeling, we assessed the hazard posed by Cirenmaco in its current status. Inter-annual variation of Cirenmaco lake area indicates a rapid lake expansion from 0.10 ± 0.08 km2 in 1988 to 0.39 ± 0.04 km2 in 2013. Bathymetric survey shows the maximum water depth of the lake in 2012 was 115 ± 2 m and the lake volume was calculated to be 1.8 × 107 m3. Field geomorphic analysis shows that Cirenmaco glacial lake is prone to GLOFs as mass movements and ice and snow avalanches can impact the lake and the melting of the dead ice in the moraine can lower the dam level. HEC-RAS 2D model was then used to simulate moraine dam failure of the Cirenmaco and assess GLOF impacts downstream. Reconstruction of Cirenmaco 1981 GLOF shows that HEC-RAS can produce reasonable flood extent and water depth, thus demonstrate its ability to effectively model complex GLOFs. GLOF modeling results presented can be used as a basis for the implementation of disaster prevention and mitigation measures. As a case study, this work shows how we can integrate different methods to GLOF hazard assessment.

The glaciated areas of the Himalaya often experience mass movement, glacial lake outburst flood and other associated hazards, posing threat to the communities and infrastructure in the downstream areas. A large debris flow occurred during July 16–19, 2017 near the present snout of the Gangotri Glacier in the Garhwal Himalaya, India resulting in significant geomorphological changes in the vicinity. The present study assesses the applicability of multi-source remote sensing data from satellites, unmanned aerial vehicle (UAV) and terrestrial laser scanner (TLS) along with process-based modelling to understand and quantify glacier snout dynamics and morphological changes around Gangotri Glacier in the Garhwal Himalaya of India. We show that retreat rates of Gangotri Glacier snout along the lateral flowlines are (left flowline 29.6 m year−1; right flowline 60.5 m year−1) are significantly higher compared to the central flowline (18.2 m year−1) during 2010–2020 leading to total loss in glacial ice area of 0.11 ± 0.015 km2. The snout dynamics and evolution of the new channel from the terminus of the adjoining Meru Glacier, connecting the moraine-dammed glacial lake and the Bhagirathi River, suggest that retreat of the Gangotri Glacier, intense precipitation and excessive seepage from the glacial lake were the important drivers of the debris flow in July 2017. The accumulated debris occupied an area of ~0.25 km2 near the snout of the Gangotri Glacier and shifted Bhagirathi River by 36–200 ± 9.35 m towards northeast. The synergistic analysis of pre- and post-event satellite, UAV and TLS-based digital elevation models (DEMs) and satellite images indicate that about −8 ± 0.066 × 106 m3 of sediments were generated by the debris flow. The results from remote sensing data suggest that a significant portion (~60%) of the deposited debris has been transported to the downstream areas between July 16–19, 2017 and October 2, 2017. Regular monitoring of the area is recommended, especially in light of climate change using earth observation data and ground measurements. The multi-source integrated framework implemented in this study is generic and can be applied for any debris flow or landslide studies in glaciated terrain.

Climatic changes alter the climate system, leading to a decrease of glacier mass volumes and swelling glacial lakes. This study provides a new inventory of glacial and high-altitude lakes for Sikkim, Eastern Himalaya, and evaluates the susceptibility of lakes to Glacial Lake Outburst Flood (GLOF). By using satellite data of high spatial resolution (5 m), we obtain 1104 glacial and high-altitude lakes with total area 30.498 km 2 , of which 472 have an area > 0.01 km 2 . Applying pre-defined GLOF susceptibility criteria on these 472 lakes yields 21 lakes susceptible to GLOF, which all increased in area from 1972–2015. Using Analytic Hierarchy Processes (AHP), the pairwise comparison matrix further reveals that 5 of these glacial lakes have low, 14 have medium and 2 have high GLOF susceptibility. Especially these 16 glacial lakes with high and medium GLOF susceptibility may threaten downstream communities and infrastructure and need further attention.

The environmental challenges posed by global warming in the Himalayan region include early and rapid melting of snow and glaciers, creation of new lakes, and expansion of old ones posing a high risk of glacial lakes outburst flood (GLOF) hazard for downstream communities. According to various elevation ranges, 3044 lakes were analyzed basinwide in the Hindu Kush-Karakoram-Himalaya (HKH) ranges of Pakistan using multisensor remote sensing data of the 2001–2013 period. An overall increase in glacial lakes was observed at various altitudinal ranges between 2500 and 5500, m out of which noticeable change by number was within the 4000–4500 m range. The analysis carried out by glacial-fed lakes and nonglacial-fed lakes in different river basins indicated variable patterns depending on the geographic location in the HKH region. The correlation analysis of parameters like lake area, expansion rate, and elevation was performed with 617 glacial lakes distributed in various river basins of the three HKH ranges. Lake area (2013) and elevation showed a negative relationship for all basins except Hunza, Shigar, and Shyok. The correlation between the expansion rate of lakes and elevation was on the positive side for Swat, Gilgit, Shigar, and Shingo basins—a situation that may be attributed to the variable altitudinal pattern of temperature and precipitation. In order to explore such diverse patterns of lake behavior and relationship with influential factors in the HKH, detailed studies based on using high resolution image data coupled with in situ information are a prerequisite. Although an increase in lake area observed below 3500 m would be favorable for water resource management, but could be alarming in context of glacial flood hazards that need to be monitored critically on a long-term basis.

Glacial lake outburst floods (GLOFs) are a unique type of natural hazard in the cryosphere that may result in catastrophic fatalities and damages. The Himalayas are known as one of the world's most GLOF-vulnerable zones. Effective hazard assessments and risk management require a thorough inventory of historical GLOF events across the Himalayas, which is hitherto absent. Existing studies imply that numerous historical GLOF events are contentious because of discrepant geographic coordinates, names, or outburst time, requiring further verifications. This study reviews and verifies over 60 historical GLOF events across the Himalayas using a comprehensive method that combines literature documentations, archival remote sensing observations, geomorphological analysis, and field investigations. As a result, three unreported GLOF events were discovered from remote sensing images and geomorphological analysis. Eleven suspicious events were identified and suggested to be excluded. The properties of five outburst lakes, i.e., Degaco, Chongbaxia Tsho, Geiqu, Lemthang Tsho, and a lake on Tshojo Glacier, were corrected or updated. A total of 51 GLOF events were verified to be convincing, and these outburst lakes were classified into three categories according to their statuses in the past decades, namely disappeared (12), stable (30), and expanding (9). Statistics of the verified GLOF events show that GLOF tended to occur between April and October in the Himalayas. We suggest that more attention should be paid to rapidly expanding glacial lakes with high possibility of repetitive outbursts. This study also demonstrates the effectiveness of integrating remote sensing and geomorphic interpretations in identifying and verifying GLOF events in remote alpine environments. This inventory of GLOFs with a range of critical attributes (e.g., locations, time, and mechanisms) will benefit the continuous monitoring and prediction of potentially dangerous glacial lakes and contribute to outburst-induced risk assessments and hazard mitigations.

We present the study of a subglacial drainage system that developed in the base of the Scandinavian Ice Sheet at the border of the Silesian Lowland and Silesian Upland (southern Poland) during the Drenthian Glaciation as a result of large outburst flood events. This drainage system was characterised by a spatially complex structure, i.e. it was composed of an individual an N-channel (tunnel channel) incised in Mesozoic rocks, i.e. Cretaceous and Triassic marls and limestones, and an R-channel, deposits of which form a set of large esker ridges which also occur on bedrock in the SE prolongation of the tunnel channel. Unlike most known cases of the co-occurrence of such forms, the studied tunnel channel and eskers are directly related, having been formed during the same flow events. The studied forms are unique within the entire southern sector of the Scandinavian Ice Sheet, which, in Central Europe, advanced mainly over soft unconsolidated Quaternary and Neogene sediments. The tunnel channel was formed as a result of enormous erosion of the ice sheet bed. The material eroded from the channel was partially deposited in a subsequent part of the drainage system. The location and orientation of the drainage system did not result directly from water pressure gradients, but was strongly determined by the internal structure of the ice sheet, i.e. it presumably developed along the marginal part of the ice stream supplying the Upper Odra ice lobe, which represented distinct weaknesses within the ice sheet. The development of the drainage system was the effect of the drainage of meltwater stored in the ice sheet system, most probably as a supraglacial lake. Gravelly-sandy rhythms recorded within the esker succession indicate that the process of lake drainage took place in several stages, or that the lake developed and drained several times.

Near the Pleistocene Termination, a glacier-dammed lake in central British Columbia suddenly drained to the south along the Fraser River valley. Floodwater travelled 330 km down the valley to Hope, British Columbia, and from there to the west into the Salish Sea near Vancouver. The flood was caused by the failure of an ice dam formed by the terminus of glaciers flowing from the central Coast Mountains across the British Columbia Interior Plateau. The ice dam impounded several hundred cubic kilometres of water to a maximum elevation of about 810 m asl (above sea level); at its maximum, the lake at the ice dam was over 250 m deep. Geomorphic and sedimentary evidence for the flood includes streamlined boulder-strewn bars, gravel dune fields, and terraces sloping up Fraser and lowermost Thompson valleys, opposite the present direction of river flow. The gravel bars and flood terraces are underlain by sheets of massive to poorly sorted gravel containing large boulders and rip-up clasts of silt and till. Shortly after the flood, a landslide near the northern margin of the former glacier dam impounded water to an elevation of about 550 m asl. This lake emptied due to overflow and incision of the landslide dam. The outburst flood from glacial Lake Fraser and the subsequent draining of the landslide-dammed lake deeply incised the older sediment fill in Fraser Valley and transported much of this sediment into the proto-Salish Sea west of Vancouver, British Columbia and Bellingham, Washington. TCN ages on flood-transported boulders at three localities along the flood path agree with radiocarbon ages on inferred flood layers in ODP cores collected from Saanich Inlet, a fiord on southern Vancouver Island, 80 km south-southwest of Vancouver.

This paper discusses Howard et al. (2012) who reconstruct the peak discharge of a glacial outburst flood, or ‘jökulhlaup’, for part of the Jökulsá á Fjöllum in north-central Iceland. They propose that this flood was the largest on Earth.Weconsider that the magnitude of the jökulhlaup proposed by Howard et al. (2012) warrants much more robust field evidence and demands more carefully parameterised hydraulic modelling. For these reasons we firstly (i) present their study in the context of previous research (ii) highlight issues with attributing landforms and sediments to jökulhlaups, and (iii) consider uncertainty regarding the timing and magnitude of jökulhlaups along the Jökulsá á Fjöllum. We argue herein that whilst a range of landforms and sediments that are attributable to jökulhlaups can be observed along the Jökulsá á Fjöllum, these are not necessarily diagnostic of jökulhlaups. Secondly, we critically discuss (iv) the major underlying assumptions of their study, and (v) their calculations and subsequent interpretations. These assessments lead us to consider that the proposal by Howard et al. (2012) of the largest flood on Earth is highly unrealistic, especially when due consideration is given to a possible source area and a trigger mechanism.

Catastrophic partial drainage of Pangong Tso, one of the largest lakes in Tibet, is supported by the geomorphology of the Tangtse Valley, Ladakh, northern India and cosmogenic 10Be nuclide ages of roche moutonnees, strath terraces, and a flood deposit downstream from the former spillway. The former spillway for Pangong Tso is ~ 20-m-high and likely allowed ~ 18 km3 of water to drain catastrophically down the Tangtse Valley over a period of about 2 days sometime during the latest Pleistocene to early Holocene. The largest flood deposit, composed of imbricated granitic boulders up to 4.5 m in length, is present ~ 33 km downvalley of the spillway. These boulders have a cosmogenic 10Be exposure age of 11.1 ± 1.0 ka, the age of the outburst flood. The minimum calculated discharge was ~ 110,000 m3 s− 1. One set of strath terraces, upvalley of the flood deposit along the flood's drainage path, shows that the rate of fluvial incision 0.3 ± 0.1 mm y− 1 during 122–10.5 ka increased to 1.5 ± 0.5 mm y− 1 during 10.5 ka to the present. The temporal overlap of this increase in the rate of fluvial incision with the main flood deposit suggests that the flood was important in defining the incision along the Tangste valley. A second set of strath terraces shows little change in incision, from ~ 0.6–0.9 to ~ 0.9–1.4 mm y− 1, sometime between 18 and 27 ka. Roche moutonnees, upvalley from strath terraces, yield a cosmogenic 10Be age of 35.8 ± 3.0 ka, defining the time when glaciers last occupied the Tangtse valley. However, the lack of glacial sediment along the Tangste valley suggests that the flood eroded glacial depositional landforms and sediments resulting in high sediment loads in the floodwater, which in turn increased fluvial incision to form strath terraces. Much of the eroded glacial sediment was subsequently redeposited as the main flood deposit. The catastrophic drainage of Pangong Tso may be the result of breaching of the Pangong–Tangste spillway during very high lake levels in a period of intensified monsoon (10.7–9.6 ka) and/or possibly the consequence of seismic activity along the Karakoram Fault that is associated with the initial formation of Pangong Tso.

The Central Karakoram, which includes K2 in Pakistan, is one of the most rapidly rising areas on Earth and exhibits complex topography and extreme relief. Impressive valley fills and glacial landforms are present throughout the valleys. The dynamics of landscape evolution of the region are currently not well understood. Consequently, the landforms were mapped and assessed in the Skardu, Shigar, and Braldu valleys, to elucidate the spatio-temporal scale dependencies of surface processes active in the region. These valleys were examined using geomorphic field methods, remote sensing, geomorphometry, and terrestrial cosmogenic nuclides (TCNs) surface exposure dating. The glaciers in this region have oscillated considerably throughout the Late Quaternary, and four glacial stages have been recognized including at least six glacial advances. Surface processes readjusted after glacier retreat, and ubiquitous mass movements and catastrophic landsliding transported material from steep slopes to valley bottoms, while glaciofluvial meltwater and glacier outburst floods redistributed sediment down valley. Glacier geochronology and late Holocene ages of the outburst flood deposits indicate that landscape evolution has been dominated by glaciation and paraglaciation during the late Quaternary.

We investigated drainage events from a glacier-dammed lake on Bear Glacier, Alaska, and associated outburst floods and hazards. The glacier-dammed lake, which we call Ice Lake, is 17.5 km up-glacier from Bear Glacier's terminus at Bear Glacier Lake. We combine field observations and remote sensing to examine temporal changes in the size of Ice Lake, the frequency and timing of its drainage, and down-glacier propagation of its outburst floods. We found that in recent years, Ice Lake has likely drained every year or two, in late summer or fall (August–October), with outbursts generally following the damming of sufficient water to create a lake area of between 0.35 and 0.5 km2. Ice Lake has migrated downvalley to the south since the 1990s, likely as a result of thinning of the glacier that dams it. In situ measurements of a drainage event in October 2010 showed that Ice Lake drained over a period of days, which manifested at Bear Glacier Lake as a gradual, multiday increase and then decrease in water levels. Glacial lake outburst flooding at Bear Glacier creates risks for sea kayakers in Bear Glacier Lake and may be relevant to understanding the effects of climate warming on glacier-dammed and proglacial lakes.

Outburst flooding from subglacial reservoirs and associated surging of ice-streams are caused by processes following climatic cooling that produce ice-shelf grounding on proglacial sills trapping subglacial water, according to an hypothesis presented here. Glaciers often advance into proglacial water bodies. Cooling may allow ice-shelf formation and advance causing grounding on a proglacial sill, trapping subglacial water. Ice-shelf freeze-on to the sill and development of a local reversal in ice–air surface slope over the sill then are likely, allowing ice thickening and water overpressurization. If basal thawing then occurs, as is likely, an outburst flood and a surge may be triggered. These processes may have been involved in Heinrich events, generation of Antarctic subglacial lakes, and meltwater scouring of some regions.

At least one large, late Pleistocene flood traveled into the Owyhee River as a result of a rise and subsequent outburst from pluvial Lake Alvord in southeastern Oregon. Lake Alvord breached Big Sand Gap in its eastern rim after reaching an elevation of 1292 m, releasing 11.3 km 3 of water into the adjacent Coyote Basin as it eroded the Big Sand Gap outlet channel to an elevation of about 1280 m. The outflow filled and then spilled out of Coyote Basin through two outlets at 1278 m and into Crooked Creek drainage, ultimately flowing into the Owyhee and Snake Rivers. Along Crooked Creek, the resulting flood eroded canyons, stripped bedrock surfaces, and deposited numerous boulder bars containing imbricated clasts up to 4.1 m in diameter, some of which are located over 30 m above the present-day channel. Critical depth calculations at Big Sand Gap show that maximum outflow from a 1292- to 1280-m drop in Lake Alvord was ∼ 10,000 m 3 s − 1 . Flooding became confined to a single channel approximately 40 km downstream of Big Sand Gap, where step-backwater calculations show that a much larger peak discharge of 40,000 m 3 s − 1 is required to match the highest geologic evidence of the flood in this channel. This inconsistency can be explained by (1) a single 10,000 m 3 s − 1 flood that caused at least 13 m of vertical incision in the channel (hence enlarging the channel cross-section); (2) multiple floods of 10,000 m 3 s − 1 or less, each producing some incision of the channel; or (3) an earlier flood of 40,000 m 3 s − 1 creating the highest flood deposits and crossed drainage divides observed along Crooked Creek drainage, followed by a later 10,000 m 3 s − 1 flood associated with the most recent shorelines in Alvord and Coyote Basins. Well-developed shorelines of Lake Alvord at 1280 m and in Coyote Basin at 1278 m suggest that after the initial flood, postflood overflow persisted for an extended period, connecting Alvord and Coyote Basins with the Owyhee River of the Columbia River drainage. Surficial weathering characteristics and planktonic freshwater diatoms in Lake Alvord sediment stratigraphically below Mt. St. Helens set Sg tephra, suggest deep open-basin conditions at ∼ 13–14 ka ( 14 C yr) and that the flood and prominent shorelines date to about this time. But geomorphic and sedimentological evidence also show that Alvord and Coyote Basins held older, higher-elevation lakes that may have released earlier floods down Crooked Creek.

Quantitative assessments of landslide hazard usually employ empirical, heuristic, deterministic, or statistical methods to derive estimates of magnitude–frequency distributions of landsliding. The formation and failure of landslide dams are common geomorphic processes in mountain regions throughout the world, causing a series of consequential off-site hazards such as catastrophic outburst floods, debris flows, backwater ponding, up- and downstream aggradation, and channel instability. Conceptual and methodological problems of quantifying geomorphic hazard from landslide dams result from (a) aspects of defining “landslide-dam magnitude”, (b) scaling effects, i.e. the geomorphic long-range and long-term implications of river blockage, and (c) paucity of empirical data. Geomorphic hazard from a landslide dam-break flood on the basis of conditional probabilities is being analysed for the alpine South Westland region of New Zealand, where formation and failure of landslide dams is frequent. Quantification of the annual probability of landsliding and subsequent dam formation in the area is limited by historical and only partially representative empirical data on slope instability. Since landslide-dam stability is a major control governing the potential of catastrophic outburst flooding, the ensuing hazard is best assessed on a recurring basis. GIS-based modelling of virtual landslide dams is a simple and cost-effective approach to approximate site-specific landslide dam and lake dimensions, reservoir infill times, and scaled magnitude of potential outburst floods. Although crude, these order-of-magnitude results provide information critical to natural hazard planning, mitigation, or emergency management decisions.

Jokulhlaups (glacial outburst floods) are known to have drained along the Jokulsa a Fjollum river in Iceland during the Holocene. However, little is known about their number, age, source, and flow characteristics. This paper provides detailed geomorphological evidence for jokulhlaups that have routed from the Kverkfjoll ice margin and hence into the Jokulsa a Fjollum. Erosional evidence of jokulhlaups from Kverkfjoll includes gorges, cataracts, spillways, subaerial lava steps, and valley-wide scoured surfaces. Depositional evidence includes wash limits, boulder bars, cataract-fill mounds, terraces, slackwater deposits, and outwash fans. Some of these landforms have been documented previously in association with jokulhlaups. However, subaerial lava surfaces that have been scoured of the upper clinker, gorges within pillow–hyaloclastite ridges, gorges between pillow–hyaloclastite ridges and subaerial lava flows, subaerial lava lobe steps, cataract-fill mounds, and boulder run-ups are previously undocumented in the literature. These landforms may therefore be diagnostic of jokulhlaups within an active volcanic rifting landscape. The nature and spatial distribution of these landforms and their stratigraphic association with other landforms suggest that there have been at least two jokulhlaups through Kverkfjallarani. The Biskupsfell eruption occurred between these two jokulhlaups. Kverkfjallarani jokulhlaups were very strongly influenced by topography, geology, and interevent processes that together determined the quantity and nature of sediment availability. Such controls have resulted in jokulhlaups that were probably fluidal, turbulent, and supercritical over large areas of the anastomosing channel bed. Kverkfjallarani jokulhlaups would have had highly variable hydraulic properties, both spatially and temporally. The knowledge of flow characteristics that can be gained from jokulhlaup impacts has implications for recognising jokulhlaups in the rock record and for hazard analysis and mitigation within similar landscapes and upon other glaciated volcanoes.

While the paper by Alley et al. (Alley, R.B., Dupont, T.K., Parizek, B.R., Anandakrishnan, S., Lawson, D.E., Larson, G.J., Evenson, E.B., 2006. Outburst flooding and the initiation of ice-stream surges in response to climatic cooling: A hypothesis. Geomorphology 75, 76–89) is a welcome contribution as it presents some new arguments and expands the discussion, it unfortunately overlooked the literature on the captured ice shelf (CIS) hypothesis. Considering all recent results, the hypothesis has the potential for drastically altering our understanding of sudden climate change during the Quaternary period. Also, the interpretation of macrogeomorphology in land-ice covered continents and seas, including the Hudson Bay and the Baltic Sea, is affected.

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

The Yangtze River is the longest watercourse in China, where it flows through the most densely populated and richest regions. The upper course of the River (Jinsha River) has been recurrently blocked over the course of time. The dam-outburst flood process has exerted a significant impact on the river's drainage area. However, the frequency of such events along the course of the Yangtze River remains poorly investigated. In this study, damming chain sediments were identified in the First Bend area of the Yangtze River, and were dated using optically stimulated luminescence (OSL) and 14C techniques. The obtained ages would suggest that the river was dammed by a debris flow during the ~20–7 ka period, with a resulting paleolake covering an area of 40.79 km2 and having a water volume of 0.63 km3. Two outburst megafloods occurred at ~18–20 and ~ 6.0 ka, respectively. The river was re-dammed again during 1.5–0.4 ka, with a lake coverage of 28.20 km2 and water volume of 0.28 km3. The dammed lake may have been gradually breached after ~0.4 ka. The damming events were caused by debris flows triggered by glacial advances on Yulong Mountain.