Moraine-dammed Lakes Research Articles

Glacial lakes in Austria - Distribution and formation since the Little Ice Age

Abstract Glacial lakes constitute a substantial part of the legacy of vanishing mountain glaciation and act as water storage, sediment traps and sources of both natural hazards and leisure activities. For these reasons, they receive growing attention by scientists and society. However, while the evolution of glacial lakes has been studied intensively over timescales tied to remote sensing-based approaches, the longer-term perspective has been omitted due a lack of suitable data sources. We mapped and analyzed the spatial distribution of glacial lakes in the Austrian Alps. We trace the development of number and area of glacial lakes in the Austrian Alps since the Little Ice Age (LIA) based on a unique combination of a lake inventory and an extensive record of glacier retreat. We find that bedrock-dammed lakes are the dominant lake type in the inventory. Bedrock- and moraine-dammed lakes populate the highest landscape domains located in cirques and hanging valleys. We observe lakes embedded in glacial deposits at lower locations on average below 2000 m a.s.l. In general, the distribution of glacial lakes over elevation reflects glacier erosional and depositional dynamics rather than the distribution of total area. The rate of formation of new glacial lakes (number, area) has continuously accelerated over time with present rates showing an eight-fold increase since LIA. At the same time the total glacier area decreased by two-thirds. This development coincides with a long-term trend of rising temperatures and a significant stepping up of this trend within the last 20 years in the Austrian Alps.

Definition and classification system of glacial lake for inventory and hazards study

Glacial lakes are not only the important refresh water resources in alpine region, but also act as a trigger of many glacial hazards such as glacial lake outburst flood (GLOF) and debris flow. Therefore, glacial lakes play an important role on the cryosphere, climate change and alpine hazards. In this paper, the issues of glacial lake were systematically discussed, then from the view of glacial lake inventory and glacial lake hazards study, the glacial lake was defined as natural water mainly supplied by modern glacial meltwater or formed in glacier moraine’s depression. Furthermore, a complete classification system of glacial lake was proposed based on its formation mechanism, topographic feature and geographical position. Glacial lakes were classified as 6 classes and 8 subclasses, i.e., glacial erosion lake (including cirque lake, glacial valley lake and other glacial erosion lake), moraine-dammed lake (including end moraine-dammed lake, lateral moraine-dammed lake and moraine thaw lake), ice-blocked lake (including advancing glacier-blocked lake and other glacier-blocked lake), supraglacial lake, subglacial lake and other glacial lake. Meanwhile, some corresponding features exhibiting on remote sensing image and quantitative indices for identifying different glacial lake types were proposed in order to build a universal and operational classification system of glacial lake.

Experimental study on the applicability of Westergaard\u2019s formula for calculating earthquake-induced hydrodynamic pressure in small lake

Moraine-dammed lake outbursts usually threaten highways, railways, and key facilities in alpine regions. The varying amplitudes and distribution of hydrodynamic pressures significantly affect the stability of the dam. We utilize a shaking table to investigate the development of hydrodynamic pressure caused by different sinusoidal waves and seismic Wolong wave. A series of shaking table tests indicate that the hydrodynamic pressure variation significantly follows seismic acceleration wave motion. The maximum hydrodynamic pressures calculated by Westergaard’s equation are compared with the experimental values under different waves. It is shown that the Westergaard’s values are lower than the experimental ones under the sinusoidal waves. However, the Westergaard’s method is able to predict the earthquake-induced hydrodynamic pressure caused by Wolong wave in small lake with desirable accuracy.

Geomorphologically effective floods from moraine-dammed lakes in the Cordillera Blanca, Peru

Outburst floods originating in moraine-dammed lakes represent a significant geomorphological process as well as a specific type of threat for local communities in the Cordillera Blanca, Peru (8.5°–10° S; 77°–78° W). An exceptional concentration of catastrophic floods has been reported from the Cordillera Blanca in the first half of 20th Century (1930s–1950s), leading to thousands of fatalities. The main objective of this paper is to provide a revised and comprehensive overview of geomorphologically effective floods in the area of interest, using various documentary data sources, verified by analysis of remotely sensed images (1948–2013) and enhanced by original field data. Verified events (n = 28; 4 not mentioned before) are analysed from the perspective of spatiotemporal distribution, pre-flood conditions, causes, mechanisms and geomorphological impacts as well as socioeconomical consequences, revealing certain patterns and similar features. GLOFs are further classified according to their magnitude: 5 extreme events, 8 major events and 15 minor events are distinguished, referring to the quantified geomorphological and socioeconomical impacts. Selected moraine dams and flood deposits are dated using lichenometric dating. Special attention is given to moraine dam breaches - the most frequent type of water release with the most significant consequences. Selected major events and their consequences are studied in detail in a separate section. Finally, a general schematic model of lake formation, growth and post-flood evolution reflecting initial topographical setting and glacier retreat is introduced and the utilization of the obtained results is outlined.

TerraSAR-X/TanDEM-X data for natural hazards research in mountainous regions of Uzbekistan

Accurate and up-to-date digital elevation models (DEMs) are important tools for studying mountain hazards. We considered natural hazards related to glacier retreat, debris flows, and snow avalanches in two study areas of the Western Tien-Shan mountains, Uzbekistan. High-resolution DEMs were generated using single TerraSAR-X/TanDEM-X datasets. The high quality and actuality of the DEMs were proved through a comparison with Shuttle Radar Topography Mission, Advanced Spaceborne Emission and Reflection Radiometer, and Topo DEMs, using Ice, Cloud, and Land Elevation Satellite data as the reference dataset. For the first study area, which had high levels of economic activity, we applied the generated TanDEM-X DEM to an avalanche dynamics simulation using RAMMS software. Verification of the output results showed good agreement with field observations. For the second study area, with a wide spatial distribution of glaciers, we applied the TanDEM-X DEM to an assessment of glacier surface elevation changes. The results can be used to calculate the local mass balance in glacier ablation zones in other areas. Models were applied to estimate the probability of moraine-dammed lake formation and the affected area of a possible debris flow resulting from glacial lake outburst. The natural hazard research methods considered here will minimize costly ground observations in poorly accessible mountains and mitigate the impacts of hazards on the environment of Uzbekistan.

Little Ice Age mapping as a tool for identifying hazard in the paraglacial environment: The case study of Trentino (Eastern Italian Alps)

The Little Ice Age (LIA) is a well-recognized climatic event during which the glaciers in the Alps advanced and reached their maximum Holocene extent. During their retreat following the LIA, the glaciers left large areas of loose or poorly consolidated glacial deposits in their forelands, which are subject to paraglacial reworking and may represent potential hazards for human infrastructures. In this study, we present a regional scale mapping of the LIA and post-LIA glacial deposits and a reconstruction of the maximum LIA extents of glaciers in the same area. This work is motivated by a local law requiring the classification of areas subject to natural hazards in Trentino (Italian Alps). Results highlight that glaciers shrunk by 63% from the LIA maximum, leaving 30km2 of unconsolidated deposits, which are subject to geomorphic paraglacial processes. Potentially hazardous consequences can occur, in particular, during high-magnitude instantaneous events, causing debris and mud flows, mass wasting from debris-covered ice, and floods from small moraine-dammed lakes.

Anatomy of terminal moraine segments and implied lake stability on Ngozumpa Glacier, Nepal, from electrical resistivity tomography (ERT)

Moraine-dammed lakes at debris-covered glaciers are becoming increasingly common and pose significant outburst flood hazards if the dam is breached. While moraine subsurface structure and internal processes are likely to influence dam stability, only few sites have so far been investigated. We conducted electrical resistivity tomography (ERT) surveys at two sites on the terminal moraine complex of the Ngozumpa Glacier, Nepal, to aid assessment of future terminus stability. The resistivity signature of glacier ice at the site (100–15 kΩ m) is more consistent with values measured from cold glacier ice and while this may be feasible, uncertainties in the data inversion introduce ambiguity to this thermal interpretation. However, the ERT data does provide a significant improvement to our knowledge of the subsurface characteristics at these sites, clearly showing the presence (or absence) of glacier ice. Our interpretation is that of a highly complex latero-terminal moraine, resulting from interaction between previous glacier advance, recession and outburst flooding. If the base-level Spillway Lake continues to expand to a fully formed moraine-dammed glacial lake, the degradation of the ice core could have implications for glacial lake outburst risk.

On a possibility to use the remote sensing techniques for glaciological analysis in mountain regions of Uzbekistan

The ALOS/AVNIR-2 satellite data (2007–2010) allowed estimating areas of glaciers, change in the areas for 50 years, and the number and areas of new naturally-dammed lakes in the mountain regions of Uzbekistan. Boundaries of these gla‑ ciers together with the ALOS/PALSAR data (2010) were used as the basis to determine position of the firn line. It was revealed that since 1980s elevation range of the line gradually decreased. The relationship between average elevation of the firn line and the upper limit of the juniper tree occurrence as well as changing of this relation since 1980s are consid‑ ered. The revealed lakes served as the basis for verification of probabilistic model of the moraine-dammed lake forma‑ tions due to the glacier recessions in the basins under consideration. It was shown that the GIS-techniques based on the use of this model together with data on glaciation and the relief digital model may significantly simplify searching of new lakes. Application of a system of the mudflow movement modeling makes possible to estimate a risk level in a case of a lake bursting. Current information about changing elevations of the glacier surfaces was obtained duet to the radar inter‑ ferometry and the altimeter data. The digital model of the river Pskem upper course (the DEM) had been built using the satellite TerraSAR‑X/TanDEM‑X data (2011–2012). All datasets of the elevations were checked for horizontal shifts of the relief digital models relative to the ICESat profiles (2003–2008). Evaluation of accuracy and morphological analysis of all the relief models for the investigated region were also made. DEMs differencing, the difference between ICESat measure‑ ments and DEM, nearby ICESat footprints within one track and between the tracks were carried out to assess the change in elevations of the glacier surfaces. Average rate of the surface lowering of an individual glacier with the maximal number of footprints (7) in the track is equal to −1 m/year; on average for 7 corrie-valley glaciers with northern/north-eastern exposition, it is −1.3 m/year in the ablation zone. This rate increases toward to the glacier terminus. Average local mass balance in the ablation zone of the Barkrak Glacier is egual to −0.82±0.36 m w.e. a−1 for the period since 2000 till 2012.

Reconstruction of Grønfjordbreen dynamics (West Spitsbergen) in the Holocene

In the past 80 years, the Grønfjord Glacier front retreated for a distance longer than 2.5 km, and thus, a big part of the proglacial zone became free of ice. The detailed geomorphological survey of this zone made pos‑ sible to identify the following landforms: exaration-glacial, glacial-accumulative, exaration-extrusive, pushmoraine (thrusting), fluvioglacial and limnoglacial ones. Geomorphological analysis of the forms indicat‑ ing the Grønfjord Glacier movement and degradation allowed establishing its dynamics over the last glacial cycle. The river running from the moraine-dammed lake erodes a great thickness of a push-moraine (up to 20‑25 m) which is composed by marine sediments, accumulated on the site of the present-day proglacial zone under a relatively higher sea level than now. Careful investigation of lithology and stratigraphy of the push-moraine together with radiocarbon dating of marine shells resulted in determination of chronology of the main sedimentation stages during the Holocene within area of the present-day proglacial zone. During the reconstruction evidences of only two stages of the significant Grønfjord Glacier advance were revealed: in the early Holocene (9.5‑10 thousand years ago) and in the little ice age (before beginning of XX century), with the maximum advance at the last stage. Basing on the results of the reconstruction the suggestion had been made that during the little ice age the Grønfjord Glacier was a surging one.

Temporal analysis of GLOFs in high-mountain regions of Asia and assessment of their causes

Glacial lake outburst flood (or shortly GLOF) has become a well-known phenomenon, one of natural hazards occurring in glaciated high mountain areas of the world. The aim of this study was to investigate temporal distribution of these events in Asia and to assess causes of lake outbursts. Therefore, a search of scientific literature and reports was carried out resulting in 219 flood cases found. In order to detect possible differences in temporal distribution a group of ice-dammed lakes was detached and compared with the rest. Concerning spatial distribution of GLOFs, it is influenced by availability of scientific literature which is determined by research teams’ region interest. Temporal analysis revealed a certain pattern in ice-dammed lake outburst distribution and notable difference between the two lake groups in terms of outburst occurrence within a year. The moraine-dammed lake outbursts were recorded earlier in an ablation season (compared to ice-dammed lakes) which could be attributed to different mechanism of dam failure. Majority of lake outburst causes were included in the category of dynamic causes (e.g. ice avalanche), long-term causes (e.g. dead-ice melting) were less represented. Results of the study imply there can be notable variations of temporal distribution and causes of GLOFs among individual mountain regions even within one continent. Therefore, varying behavior of potentially dangerous lakes should be taken into consideration when, for instance, proposing mitigation measures.

Identification of landslide-prone zones in the geomorphically and climatically sensitive Mandakini valley, (central Himalaya), for disaster governance using the Weights of Evidence method

The entire Himalayan region is prone to disasters, with many people being vulnerable to hydroclimatic threats such as extreme rainfall-driven floods, glacial lake outburst floods (GLOFs), landslide lake outburst floods (LLOFs), and landslides triggered by rainfall. Landslides and floods are related, as the former cause the lakes that burst, and floods can undercut slopes and cause landslides. During the past 200years, landslides and floods caused by LLOFs in the Garhwal Himalaya have occurred in 1894, 1970, and 1978; but the most disastrous event, in terms of loss of life and economic impact, occurred in June 2013, which was a result of extreme rainfall in the Higher Himalaya and breaching of a moraine-dammed lake, very short-lived LLOFs, and rainfall-induced runoff and landslides. Outmigration from the area as a result of the 2013 event has caused anxiety about the future of the economy and also concerns about security of a state that has an international border. As a contribution to planning and reconstruction to secure the livelihoods of the local people and to entice migrants to return, this paper identifies zones in the Mandakini valley susceptible to landslides using a ‘Weights of Evidence’ approach. The roles of climate, geology, and geomorphology of the valley are also given attention to explain the reasons for the disastrous event of June 2013. The results of the research presented here may be an important input to disaster governance.

882 lakes of the Cordillera Blanca: An inventory, classification, evolution and assessment of susceptibility to outburst floods

An inventory of the lakes within the Cordillera Blanca of Peru was made based on manual analysis of high resolution optical images and was verified during field surveys. In total, 882 lakes were detected, classified and described by several qualitative and quantitative characteristics. The majority of the lakes were characterised as moraine-dammed lakes (35.2%), followed by bedrock-dammed lakes (31.3%), while ice-dammed and landslide-dammed lakes were quite rare with 3.5% and 2.6%, respectively. Two thirds of the lakes (66.5%) have a surface area<10,000m2 and are classified as being small, while only 7.3% are classified as large lakes with an area>100,000m2. The majority of the large lakes are characterised as moraine-dammed lakes (48.4%) and the share of landslide-dammed lakes is significantly increased to 12.4% in this class. In the 1950s, most lakes were situated in the elevation range of 4250–4600a.s.l. (Concha, 1951), while 49.4% of the lakes are currently situated above 4600ma.s.l. This elevational shift is considered to be a result of ongoing environmental change and glacier retreat within the Cordillera Blanca. By analysing multi-temporal aerial images covering the period from 1948 to 2013 it was shown that glacial lakes in already deglaciated catchments may persist for long periods of time without any areal change. It was also shown that glacial lake outburst floods (GLOFs) originated from moraine-dammed lakes in the earlier stages of glacier retreat (1940s and 1950s) and from bedrock-dammed lakes in later stages (recently); however, no clear trend was revealed regarding the starting elevation of GLOFs. The susceptibility of all of the large lakes (n=64) to outburst floods was assessed. Monitoring of young proglacial lakes and large moraine-dammed lakes, systematic susceptibility reassessments considering potential future changes, and flood modelling are recommended.

Stagnation and mass loss on a Himalayan debris-covered glacier: processes, patterns and rates

ABSTRACTThe ablation areas of debris-covered glaciers typically consist of a complex mosaic of surface features with contrasting processes and rates of mass loss. This greatly complicates glacier response to climate change, and increases the uncertainty of predictive models. In this paper we present a series of high-resolution DEMs and repeat lake bathymetric surveys on Ngozumpa Glacier, Nepal, to study processes and patterns of mass loss on a Himalayan debris-covered glacier in unprecedented detail. Most mass loss occurs by melt below supraglacial debris, and melt and calving of ice cliffs (backwasting). Although ice cliffs cover only ~5% of the area of the lower tongue, they account for 40% of the ablation. The surface debris layer is subject to frequent re-distribution by slope processes, resulting in large spatial and temporal differences in debris-layer thickness, enhancing or inhibiting local ablation rates and encouraging continuous topographic inversion. A moraine-dammed lake on the lower glacier tongue (Spillway Lake) underwent a period of rapid expansion from 2001 to 2009, but later experienced a reduction of area and volume as a result of lake level lowering and sediment redistribution. Rapid lake growth will likely resume in the near future, and may eventually become up to 7 km long.

Estimating the volume of Alpine glacial lakes

Abstract. Supraglacial, moraine-dammed and ice-dammed lakes represent a potential glacial lake outburst flood (GLOF) threat to downstream communities in many mountain regions. This has motivated the development of empirical relationships to predict lake volume given a measurement of lake surface area obtained from satellite imagery. Such relationships are based on the notion that lake depth, area and volume scale predictably. We critically evaluate the performance of these existing empirical relationships by examining a global database of glacial lake depths, areas and volumes. Results show that lake area and depth are not always well correlated (r2 = 0.38) and that although lake volume and area are well correlated (r2 = 0.91), and indeed are auto-correlated, there are distinct outliers in the data set. These outliers represent situations where it may not be appropriate to apply existing empirical relationships to predict lake volume and include growing supraglacial lakes, glaciers that recede into basins with complex overdeepened morphologies or that have been deepened by intense erosion and lakes formed where glaciers advance across and block a main trunk valley. We use the compiled data set to develop a conceptual model of how the volumes of supraglacial ponds and lakes, moraine-dammed lakes and ice-dammed lakes should be expected to evolve with increasing area. Although a large amount of bathymetric data exist for moraine-dammed and ice-dammed lakes, we suggest that further measurements of growing supraglacial ponds and lakes are needed to better understand their development.

Effects of seismic surge waves and implications for moraine-dammed lake outburst

Moraine dams usually collapse due to overtopping by the surge wave in the dammed lake, and the surge wave is most likely caused by an earthquake. The seismic water wave (SWW) is a major factor causing the dam to break in the earthquake zone. This paper focused on the SWW by model experiments with a shaking water tank under conditions of various water depths, seismic waves, and peak ground accelerations. Two empirical equations were obtained for estimating maximal wave height for the low and high frequency, respectively. Finally, we present the application of the empirical equations on Midui Glacier Lake in Tibet plateau.

Detection of Glacier Lakes Buried under Snow by RISAT-1 SAR in the Himalayan Terrain

Synthetic aperture radar (SAR) signals penetrate through the dry snow and cloud providing crucial data over the Himalayan temperate glaciers and complement the optical images. In the present study, RISAT-1 C band and AWiFS images of winter/ablation period over Samudra Tapu and Gepang Gath moraine dammed lakes (MDLs) in Himachal Pradesh have been analysed. Backscattering coefficient of the lake was observed to be low throughout the year. Penetration depth of SAR into dry snowpack was calculated to vary from 4 to 22 m for a range of snow density (0.1-0.5 g/cm 3 ), whereas it was estimated to be 1.20- 2.01 m based on ground observations for 30 January and 24 February 2013. The present study provides results of RISAT-1 C-band penetration up to ~2 m through the snowpack to detect MDLs in the Himalayan terrain. The detection of MDLs using the backscattering images of winter season was validated with synchronous AWiFS sensor images.

Monitoring of Moraine-Dammed Lakes: A Remote Sensing-Based Study in the Western Himalaya

Monitoring of lakes in glaciated terrain in the Himalayan region has been recognized as one of the priority areas especially after the Kedarnath disaster. Among all types of glacial lakes, moraine dammed lakes (MDLs) are the most important from disaster point of view. Remote sensing plays a significant role in view of availability of unbiased repeated data on the expansion or contraction of MDLs located in rugged terrains of the Himalaya. Monitoring of two MDLs, associated with Katkar and Gepang-gath glaciers in Zanskar and Chandra sub-basins respectively was done using satellite images of 1965, 1976, 1989, 2001, 2006-07, 2012 and 2014. Survey of India (SOI) topographical maps of 1962 were also referred to monitor the respective glaciers lakes. SOI maps show the presence of only one lake associated with Gepang-gath glacier. Areal extent of the MDLs had increased from 21 to 57 ha between 1965 and 2014, and from 27 to 80 ha between 1962 and 2014 for the Katkar and Gepang-gath glaciers respectively. Increase in peak discharge of the two lakes was also estimated using different empirical models in case of outbursts of these lakes. The lake outburst probability for both these lakes was found to be very low (less than 1%), however, possibility of outburst of lakes due to natural calamity like cloud burst, landslide or earthquake cannot be ignored. The rate of retreat of these two glaciers was observed to be high due to the presence of MDLs in comparison to surrounding glaciers in the valley.

Monitoring of Moraine-Dammed Lakes: A Remote Sensing-Based Study in the Western Himalaya

Monitoring of Moraine-Dammed Lakes: A Remote Sensing-Based Study in the Western Himalaya

Devastation in the Kedarnath (Mandakini) Valley, Garhwal Himalaya, during 16–17 June 2013: a remote sensing and ground-based assessment

The Garhwal Himalaya tragedy of 16–17 June 2013 was perhaps the worst disaster of the last century seen in India owing to unprecedented rainfall. The extreme rainfall together with bursting of moraine-dammed Chorabari Lake caused devastating flooding of the Mandakini River and its tributaries in the Garhwal Himalaya. Several downstream settlements such as Kedarnath (3546 m a.s.l.), Rambara (2740 m a.s.l.) and Gaurikund (1990 m a.s.l.) were damaged due to flash floods. The present study was taken up to assess the extent of devastation in the Mandakini Valley from Kedarnath to Sonprayag based on ground observations, repeated ground photography, discussion with local residents (eye witnesses) and analysis of pre-event and post-event high-resolution satellite data. Overall 137 ‘flash flood-induced debris flow’ events were mapped in the Mandakini Valley between Kedarnath and Sonprayag which led to the catastrophe and miseries to the pilgrims. The area of ‘flash flood-induced debris flow’ and the main channel of Mandakini River were increased by ~575 and ~406 %, respectively, during the 16–17 June 2013 event. About 50 % (7 km) of the pedestrian route (14 km) between Gaurikund and Kedarnath was completely washed away which obstructed the rescue operations to evacuate pilgrims, tourists and local people after the 16–17 June 2013 event. The ‘flash flood-induced debris flow’ and moraine-dammed lake outburst events together washed away ~120 and ~90 buildings around Kedarnath shrine and in Rambara town, respectively, although the main Kedarnath temple survived with minor damage. The database of flash flood-induced debris flows and flood effected area generated in the present research will facilitate to other disciplines (e.g., future settlements planning) for long-term reconstruction work in the affected areas of the Mandakini Valley.

A high-resolution simulation of catastrophic rainfall over Uttarakhand, India

On 16 June 2013, intense and continuous rainfall together led to the collapse of moraine-dammed lake (Chorabari Lake) and devastated the entire land of Uttarakhand, Himalaya. This caused heavy floods in Uttarakhand (28°43′−31°27′ latitudes and 77°34′–81°02′ longitudes) along with unprecedented damage to life and property. Timely prediction and warning of such severe local weather systems over complex terrain are the first step towards disaster mitigation and bears huge societal impact. In this study, weather research and forecasting (WRF) model was configured at high spatial resolution (2 km) to simulate the Kedarnath heavy rainfall event over Uttarakhand region of India during 16–17 June 2013. Results showed that the WRF model was able to predict the Kedarnath heavy rainfall. Location and intensity of heavy rainfall were captured by the WRF model when verified with in situ measurements and satellite-retrieved rainfall products. Moreover, the explicit impact of topography in triggering this extreme weather event has been discussed using a diagnostic model which demonstrated that orographic component of rain rate is quite high over this region.