Glacial Lake Inventory and Lake Outburst Flood/Debris Flow Hazard Assessment after the Gorkha Earthquake in the Bhote Koshi Basin

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

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Simulation and Assessment of Future Glacial Lake Outburst Floods in the Poiqu River Basin, Central Himalayas

Water ◽

10.3390/w13101376 ◽

2021 ◽

Vol 13 (10) ◽

pp. 1376

Author(s):

Taigang Zhang ◽

Weicai Wang ◽

Tanguang Gao ◽

Baosheng An

Keyword(s):

River Basin ◽

Hazard Assessment ◽

Glacial Lake ◽

High Mountain ◽

Glacial Lakes ◽

Central Himalayas ◽

Outburst Floods ◽

Glacial Lake Outburst Floods ◽

Social And Economic Development ◽

Glacial Lake Outburst Flood

A glacial lake outburst flood (GLOF) is a typical glacier-related hazard in high mountain regions. In recent decades, glacial lakes in the Himalayas have expanded rapidly due to climate warming and glacial retreat. Some of these lakes are unstable, and may suddenly burst under different triggering factors, thus draining large amounts of water and impacting downstream social and economic development. Glacial lakes in the Poiqu River basin, Central Himalayas, have attracted great attention since GLOFs originating there could have a transboundary impact on both China and Nepal, as occurred during the Cirenmaco GLOF in 1981 and the Gongbatongshaco GLOF in 2016. Based on previous studies of this basin, we selected seven very high-risk moraine-dammed lakes (Gangxico, Galongco, Jialongco, Cirenmaco, Taraco, Beihu, and Cawuqudenco) to simulate GLOF propagation at different drainage percentage scenarios (i.e., 25%, 50%, 75%, and 100%), and to conduct hazard assessment. The results show that, when any glacial lake is drained completely or partly, most of the floods will enter Nepal after raging in China, and will continue to cause damage. In summary, 57.5 km of roads, 754 buildings, 3.3 km2 of farmland, and 25 bridges are at risk of damage due to GLOFs. The potentially inundated area within the Chinese part of the Poiqu River basin exceeds 45 km2. Due to the destructive impacts of GLOFs on downstream areas, appropriate and effective measures should be implemented to adapt to GLOF risk. We finally present a paradigm for conducting hazard assessment and risk management. It uses only freely available data and thus is easy to apply.

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Debris Flows Resulting From Glacial-Lake Outburst Floods in Tibet, China

Physical Geography ◽

10.2747/0272-3646.31.6.508 ◽

2010 ◽

Vol 31 (6) ◽

pp. 508-527 ◽

Cited By ~ 14

Author(s):

Peng Cui ◽

Chao Dang ◽

Zunlan Cheng ◽

Kevin M. Scott

Keyword(s):

Debris Flows ◽

Glacial Lake ◽

Outburst Floods ◽

Glacial Lake Outburst Floods

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Role of supraglacial lakes in recession of Himalayan glaciers: A case study of Dudh Koshi basin, Nepal

Journal of Applied Geodesy ◽

10.1515/jag-2018-0002 ◽

2018 ◽

Vol 12 (3) ◽

pp. 199-207 ◽

Cited By ~ 1

Author(s):

Florencia Matina Tuladhar ◽

Diwakar KC

Keyword(s):

Interannual Variation ◽

Google Earth ◽

Glacial Lake ◽

Coefficient Of Determination ◽

Lake Area ◽

Supraglacial Lakes ◽

Glacier Recession ◽

Outburst Floods ◽

Koshi Basin

Abstract Climate change has been adversely affecting glaciers causing them to advance and recession worldwide. Existing studies have primarily attributed temperature as the leading factor causing glacier recession. However, detailed studies that investigate effect of other factors like presence of debris cover, slope, and contact with water bodies are still scarce. This research, thus investigated the role of supraglacial lakes in recession of debris-covered glaciers (DCG). Such glaciers were studied since these lakes are found in debris-covered glaciers only. For this purpose the interannual variation in area of supraglacial lakes of Dudh Koshi basin was computed to test the hypothesis that these lakes play a significant role in glacier recession. Supraglacial lakes were delineated using Google Earth Pro at five year intervals to assess interannual variation in lake area. Slope, elevation and change in supraglacial lake area were the predictors influencing average decadal change in area of glaciers. Two models prepared using multiple linear regression in Excel were compared. The first model used elevation and slope as predictors while the second model used change in supraglacial lake area as the additional predictor. The second model had a higher coefficient of determination (R square) and Adjusted R-square values of 99 % and 96 % compared to the first model. Further test statistics from Analysis of Variance (ANOVA) results were compared to test the hypothesis. Moreover the Root mean square error (RMSE) of second model was also less than the first one. Hence both the regression statistics and RMSE confirmed that change in area of supraglacial lakes was an important factor that influences overall recession of debris-covered glaciers. Nevertheless, use of high spatial and temporal resolution imageries along-with increase in number of glaciers sampled should be incorporated in future studies to ensure robust outcomes. Thus this research can bolster the overall understanding between glacier and glacial lake dynamics which will improve the resilience of downstream inhabitants from climate induced hazards, such as glacial lake outburst floods (GLOFs).

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Identifying key predictors for the susceptibility of Himalayan glacial lakes to sudden outburst floods

10.5194/egusphere-egu2020-17689 ◽

2020 ◽

Author(s):

Melanie Fischer ◽

Georg Veh ◽

Oliver Korup ◽

Ariane Walz

Keyword(s):

Logistic Regression ◽

Binary Logistic Regression ◽

Glacial Lake ◽

Occurrence Rate ◽

Past Century ◽

Glacial Lakes ◽

Mountain Areas ◽

Logistic Regression Models ◽

The Past ◽

Outburst Floods

Despite being a rather rare phenomenon when compared to the occurrence rates of other alpine hazards (e.g. landslides, avalanches), glacial lake outburst floods (GLOFs) pose a significant threat to downvalley communities in glaciated mountain areas. Characteristically high peak discharge rates and flood volumes, documented to have reached 30,000 m&#179;/s and > 50 million m&#179; in the past century, not only provide GLOFs with a landscape-forming potential but also killed a reported global total of > 12,000 people and caused severe damage to infrastructures. Extensive glacial covers and steep topographic gradients, coupled with rapidly changing socio-economical implications, make the Hindu-Kush-Himalaya (HKH) a high priority region for GLOF research, even though recent studies suggest an annual occurrence rate of 1.3 GLOFs per year across this range during the past three decades. So far, GLOF research in the greater HKH region has been predominantly focused on the classification of potentially dangerous glacial lakes derived from analysing a limited number of glacial lakes and even fewer reportedly GLOF-generating glacial lakes. Moreover, subjectively set thresholds are commonly used to produce GLOF hazard classification matrices. Contrastingly, our study is aimed at an unbiased, statistical robust and reproducible assessment of GLOF susceptibility. It is based on the currently most complete inventory of GLOFs in the HKH since the 1980&#8217;s, which comprises 38 events. In order to identify key predictors for GLOF susceptibility, a total of 104 potential predictors are tested in logistic regression models. These parameters cover four predictor categories, which describe each glacial lake&#8217;s a) topography, b) catchment glaciers, c) geology and seismicity in its surroundings, and c) local climatic variables. Both classical binary logistic regression as well as hierarchical logistic regression approaches are implemented in order to assess which factors drive susceptibility of HKH glacial lakes to sudden outbursts and whether these are regionally distinct.

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The formation of new glacial lakes at the Jostedalsbreen ice cap in southwest Norway and their future implications

10.5194/egusphere-egu2020-5012 ◽

2020 ◽

Cited By ~ 2

Author(s):

Katja Laute ◽

Achim A. Beylich

Keyword(s):

Current Trend ◽

Glacial Lake ◽

Glacier Area ◽

Glacial Lakes ◽

Economic Implications ◽

Ice Cap ◽

Western Norway ◽

Outburst Floods ◽

Glacier Length ◽

Length Changes

In recent years, the number and size of glacial lakes in mountain regions have increased worldwide associated to the climate-induced glacier retreat and thinning. Glacial lakes can cause glacial lake outburst floods (GLOFs) which can pose a significant natural hazard in mountainous areas and can cause loss of human life as well as damage to infrastructure and property.The glacial landscape of the Jostedalsbreen ice cap in south-western Norway is currently undergoing significant changes reflected by progressing glacier length changes of the outlet glaciers and the formation of new glacial lakes within the recently exposed glacier forefields. We present a new glacier area outline for the entire Jostedalsbreen ice cap and the first detailed inventory of glacial lakes which were formed within the newly exposed ice-free area at the Jostedalsbreen ice cap. In detail, we explore (i) the glacial lake characteristics and types and (ii) analyse their spatial distribution and hazard potential.For the period from 1952-1985 to 2017/2018 the entire glacier area of the Jostdalsbreen ice cap experienced a loss of 79 km2. A glacier area reduction of 10 km2 occurred since 1999-2006. Two percent of the recently exposed surface area (since 1952-1985) is currently covered with newly developed glacial lakes corresponding to a total number of 57 lakes. In addition, eleven lakes that already existed have enlarged in size. Four types of glacial lakes are identified including bedrock-dammed, bedrock- and moraine-dammed, moraine-dammed and ice-dammed lakes. Especially ice- or moraine-dammed glacial lakes can be the source of potentially catastrophic glacier lake outburst floods. According to the inventory of glacier-related hazardous events in Norway GLOFs represent the most common hazardous events besides ice avalanches and incidents related to glacier length changes. Around the Jostedalsbreen ice cap several historical but also recent events are documented. The majority of the events caused partly severe damage to farmland and infrastructure but fortunately no people have been harmed by today.Due to the predicted increase in summer temperatures for western Norway until the end of this century, it is very likely that the current trend of an accelerated mass loss of Norwegian glaciers will continue. As one consequence of this development, further new lakes will emerge within the newly exposed terrain. The development of new glacial lakes has diverse regional and global socio-economic implications. Especially in mainland Norway, where glaciers and glacier-fed streams have a high importance for hydropower production, tourism and climate research it is essential to gain a better understanding of the possible impacts of glacial lakes for being prepared for risks but also advantages arising from these newly emerging landscape elements.

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Glacial Lakes and Glacial Lake Outburst Floods in Nepal

10.53055/icimod.543 ◽

2011 ◽

Author(s):

Keyword(s):

Glacial Lake ◽

Glacial Lakes ◽

Outburst Floods ◽

Glacial Lake Outburst Floods

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New method for assessing the potential hazardousness of glacial lakes in the Cordillera Blanca, Peru

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-11-2391-2014 ◽

2014 ◽

Vol 11 (2) ◽

pp. 2391-2439 ◽

Cited By ~ 1

Author(s):

A. Emmer ◽

V. Vilímek

Keyword(s):

Slope Movement ◽

Dam Failure ◽

Glacial Lake ◽

Flood Wave ◽

Glacial Lakes ◽

Cordillera Blanca ◽

Outburst Floods ◽

Glacial Lake Outburst Floods ◽

Glacial Lake Outburst Flood ◽

Dam Overtopping

Abstract. This paper presents a new and easily repeatable objective method for assessing the potential hazardousness of glacial lakes within the Peruvian region of Cordillera Blanca (excluding ice-dammed lakes, which do not reach significant volumes in this region). The presented method was designed to meet four basic principles, which we considered as being crucial. These are: (a) principle of regional focus; (b) principle of objectivity; (c) principle of repeatability; and (d) principle of multiple results. Potential hazardousness is assessed based on a combination of decision trees for clarity and numerical calculation for objectivity. A total of seventeen assessed characteristics are used, of which seven have yet to be used in this context before. Also, several ratios and calculations are defined for the first time. We assume that it is not relevant to represent the overall potential hazardousness of a particular lake by one result (number), thus the potential hazardousness is described in the presented method by five separate results (representing five different glacial lake outburst flood scenarios). These are potentials for: (a) dam overtopping resulting from a dynamic slope movement into the lake; (b) dam overtopping following the flood wave originating in a lake situated upstream; (c) dam failure resulting from a dynamic slope movement into the lake; (d) dam failure following the flood wave originating in a lake situated upstream; and (e) dam failure following a heavy earthquake. All of these potentials theoretically range from 0 to 1. The presented method was verified on the basis of assessing the pre-flood conditions of seven lakes which have produced ten glacial lake outburst floods in the past and ten lakes which have not. A comparison of these results showed that the presented method successfully identifies the potentially hazardous lakes.

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Glacial lake variation and hazard assessment of glacial lakes outburst in the Parlung Zangbo River Basin

Journal of Lake Sciences ◽

10.18307/2019.0420 ◽

2019 ◽

Vol 31 (4) ◽

pp. 1132-1143

Author(s):

LIU Juan ◽

◽

YAO Xiaojun ◽

GAO Yongpeng ◽

QI Miaomiao ◽

...

Keyword(s):

River Basin ◽

Hazard Assessment ◽

Glacial Lake ◽

Glacial Lakes ◽

Lake Variation

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Glacial Lake Changes and Identification of Potentially Dangerous Glacial Lakes in the Yi’ong Zangbo River Basin

Water ◽

10.3390/w12020538 ◽

2020 ◽

Vol 12 (2) ◽

pp. 538

Author(s):

Hongyu Duan ◽

Xiaojun Yao ◽

Dahong Zhang ◽

Miaomiao Qi ◽

Juan Liu

Keyword(s):

River Basin ◽

Glacial Lake ◽

Glacial Lakes ◽

Huge Number ◽

First Order ◽

Outburst Floods ◽

Glacial Lake Outburst Floods ◽

Glacier Melting ◽

First Order Method ◽

Very High

The southeastern Tibetan Plateau, where monsoonal temperate glaciers are most developed, has a huge number of glacial lakes. Based on Landsat Operational Land Imager (OLI) images, 192 glacial lakes with a total area of 45.73 ± 6.18 km2 in 2016 were delineated in the Yi’ong Zangbo River Basin. Glacial lakes with areas of less than 0.1 km2 accounted for 81.77% of the total number, and glacial lakes located above 4500 m elevation comprised 83.33%. Dramatic glacier melting caused by climate warming has occurred, resulting in the formation and expansion of glacial lakes and the increase of potential glacial lake outburst floods (GLOFs) risk. From 1970 to 2016, the total area of glaciers in the basin has decreased by 35.39%, whereas the number and total area of glacial lakes have, respectively, increased by 86 and 1.59 km2. In that time, 110 new glacial lakes emerged, whereas 24 of the original lakes disappeared. The newly formed lakes have a smaller mean area but higher mean elevation than the lakes that disappeared. Based on five indicators, a first-order method was used to identify glacial lakes that pose potential threats. We identified 10 lakes with very high, 7 with high, 31 with medium, and 19 with low GLOF susceptibility, out of 67 moraine-dammed glacial lakes with areas larger than 0.02 km2. Understanding the behavior of glaciers and glacial lakes is a vital aspect of GLOFs disaster management, and the monitoring of glacial lakes should be strengthened.

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Glacial Lake Outburst Floods Early Warning System to save lives and livelihood of the Nepal Himalaya communities: A case Study of Imja Glacial Lake, Nepal

10.5194/egusphere-egu21-4163 ◽

2021 ◽

Author(s):

Deepak Kc ◽

Top Khatri ◽

Rishiram Sharma

Keyword(s):

Climate Change ◽

Risk Reduction ◽

Early Warning ◽

Early Warning System ◽

Warning System ◽

Glacial Lake ◽

Glacial Lakes ◽

Community Based ◽

Outburst Floods ◽

Glacial Lake Outburst Floods

Nepal, a mountainous country, is experiencing multiple disasters, majority of which are induced by Climate Change. Erratic rainfall, extremely high temperature during summer, cold waves are some of them. Nepal will experience the impacts of climate change through an increase in temperature, more frequent heat waves and shorter frost durations in the future (5AR IPCC). Nepal is witnessing the increased maximum temperature of 0.56oC per decade and the increment of the temperature is even higher in the mountain region (ICIMOD 2019). One of the major impacts of Climate Change among others, is glacier retreat and Glacial Lake Outburst Floods (GLOFS). Nepal has already experienced more than 26 GLOFS (UNDP and ICIMOD 2020), originated both from Nepal and China, Tibet.The Imja Glacial Lake is located at 27&#176; 53&#8242; 55&#8220; N latitude, 86&#176; 55&#8217; 20&#8221; E longitude and at an altitude of 5010&#8201;m in Everest Region of Nepal Himalayas. &#160;Imja was identified during 1960s as a small supra lake, was later expanded to an area of 1.28 Km2, 148.9 meter deep, holding 75.2 million cubic meters of water in 2014. &#160;&#160;Lake lowering by 3.4 metres and establishment of early warning system was done in 2016 by the Government of Nepal and UNDP with the support of Global Environment Facility. &#160;Hydro-met stations & GLOF Sensors in the periphery and downstream&#160; of Imja Lake and automated early warning sirens in six prime settlements in the &#160;downstream of Imja &#160;watershed &#160;linking with &#160;dynamic SMS Alert system along 50 km downstream of Imja Dudh Koshi River have been have been linked with community-based DRM institutions at local government level. This initiative is important for preparedness and response of GLOF Risk Reduction in the Imja Valley, benefitting 71,752 vulnerable people, both local and the tourists visiting the Everest Region of Nepal.Early Warning System of Tsho Rolpa Glacial Lake, the biggest Glacial Lake of Nepal is another example in the such system. New inventory of Glacial Lakes has identified 47 critical lakes as priority lakes for GLOF Risk Reduction in Koshi, Gandaki and Karnali basins. In the new context of federal &#160;governance system, the role of federal, province and local government and communities is crucial&#160; for achieving the targets of&#160; Sendai Framework for Disaster Risk Reduction , particularly target &#8220;g&#8221; and SDGs 11 and 13&#160; through integrating&#160; the targets in the regular planning and &#160;&#160;its&#8217; implementation for resilient and Sustainable Development of&#160; Nepal.References:Glacial lakes and glacial lake outburst floods in Nepal. Kathmandu, ICIMOD 2011,&#160; Nepal Disaster Report, Ministry of Home affairs (MoHA) , 2015, 2018 Annual Reports UNDP 2016, 2017 and 2018,&#160; Imja Hydro-Meteorological and Early Warning System User Manual, Government of Nepal and UNDP, 2017 Project Completion Report: Community Based Flood and Glacial Lake Outburst Risk Reduction Project, Government of Nepal and UNDP, 2017,&#160; Inventory of glacial lakes and identification of potentially dangerous glacial lakes in the Koshi, Gandaki, and Karnali River Basins of Nepal, the Tibet Autonomous Region of China, and India. Research Report, ICIMOD and UNDP, 2020&#160;

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