Numerical modelling of Glacial Lake Outburst Floods using physically based dam-breach models

Abstract. The rapid development and instability of moraine-dammed proglacial lakes is increasing the potential for the occurrence of catastrophic Glacial Lake Outburst Floods (GLOFs) in high-mountain regions. Advanced, physically-based numerical dam-breach models represent an improvement over existing methods for the derivation of breach outflow hydrographs. However, significant uncertainty surrounds the initial parameterisation of such models, and remains largely unexplored. We use a unique combination of numerical dam-breach and two-dimensional hydrodynamic modelling, employed with a Generalised Likelihood Uncertainty Estimation (GLUE) framework to quantify the degree of equifinality in dam-breach model output for the reconstruction of the failure of Dig Tsho, Nepal. Monte Carlo analysis was used to sample the model parameter space, and morphological descriptors of the moraine breach were used to evaluate model performance. Equifinal breach morphologies were produced by parameter ensembles associated with differing breach initiation mechanisms, including overtopping waves and mechanical failure of the dam face. The material roughness coefficient was discovered to exert a dominant influence over model performance. Percentile breach hydrographs derived from cumulative distribution function hydrograph data under- or overestimated total hydrograph volume and were deemed to be inappropriate for input to hydrodynamic modelling. Our results support the use of a Total Variation Diminishing solver for outburst flood modelling, which was found to be largely free of numerical instability and flow oscillation. Routing of scenario-specific optimal breach hydrographs revealed prominent differences in the timing and extent of inundation. A GLUE-based method for constructing likelihood-weighted maps of GLOF inundation extent, flow depth, and hazard is presented, and represents an effective tool for communicating uncertainty and equifinality in GLOF hazard assessment. However, future research should focus on the utility of the approach for predictive, as opposed to reconstructive GLOF modelling.

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Numerical modelling of glacial lake outburst floods using physically based dam-breach models

Earth Surface Dynamics ◽

10.5194/esurf-3-171-2015 ◽

2015 ◽

Vol 3 (1) ◽

pp. 171-199 ◽

Cited By ~ 16

Author(s):

M. J. Westoby ◽

J. Brasington ◽

N. F. Glasser ◽

M. J. Hambrey ◽

J. M. Reynolds ◽

...

Keyword(s):

Model Performance ◽

Monte Carlo Analysis ◽

Glacial Lake ◽

Roughness Coefficient ◽

High Mountain ◽

Dam Breach ◽

Outburst Floods ◽

Glacial Lake Outburst Floods ◽

Physically Based ◽

Inundation Extent

Abstract. The instability of moraine-dammed proglacial lakes creates the potential for catastrophic glacial lake outburst floods (GLOFs) in high-mountain regions. In this research, we use a unique combination of numerical dam-breach and two-dimensional hydrodynamic modelling, employed within a generalised likelihood uncertainty estimation (GLUE) framework, to quantify predictive uncertainty in model outputs associated with a reconstruction of the Dig Tsho failure in Nepal. Monte Carlo analysis was used to sample the model parameter space, and morphological descriptors of the moraine breach were used to evaluate model performance. Multiple breach scenarios were produced by differing parameter ensembles associated with a range of breach initiation mechanisms, including overtopping waves and mechanical failure of the dam face. The material roughness coefficient was found to exert a dominant influence over model performance. The downstream routing of scenario-specific breach hydrographs revealed significant differences in the timing and extent of inundation. A GLUE-based methodology for constructing probabilistic maps of inundation extent, flow depth, and hazard is presented and provides a useful tool for communicating uncertainty in GLOF hazard assessment.

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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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Reconstructing the History of Glacial Lake Outburst Floods (GLOF) in the Kanchenjunga Conservation Area, East Nepal: An Interdisciplinary Approach

Sustainability ◽

10.3390/su12135407 ◽

2020 ◽

Vol 12 (13) ◽

pp. 5407

Author(s):

Alton C. Byers ◽

Mohan Bahadur Chand ◽

Jonathan Lala ◽

Milan Shrestha ◽

Elizabeth A. Byers ◽

...

Keyword(s):

Interdisciplinary Approach ◽

Debris Avalanche ◽

Field Investigation ◽

Glacial Lake ◽

High Mountain ◽

Lateral Moraine ◽

Conservation Area ◽

Terminal Moraine ◽

Outburst Floods ◽

Glacial Lake Outburst Floods

An interdisciplinary field investigation of historic glacial lake outburst floods (GLOFs) in the Kanchenjunga region of Nepal was conducted between April and May, 2019. Oral history and field measurements suggested that at least six major GLOFs have occurred in the region since 1921. A remote sensing analysis confirmed the occurrence of the six GLOFs mentioned by informants, including two smaller flood events not mentioned that had occurred at some point before 1962. A numerical simulation of the Nangama GLOF suggested that it was triggered by an ice/debris avalanche of some 800,000 m3 of material, causing a surge wave that breached the terminal moraine and released an estimated 11.2 × 106 m3 ± 1.4 × 106 m3 of water. Debris from the flood dammed the Pabuk Khola river 2 km below the lake to form what is today known as Chheche Pokhari lake. Some concern has been expressed for the possibility of a second GLOF from Nangama as the result of continued and growing landslide activity from its right lateral moraine. Regular monitoring of all lakes and glaciers is recommended to avoid and/or mitigate the occurrence of future GLOF events in the region. Collectively, the paper demonstrates the benefits and utility of interdisciplinary research approaches to achieving a better understanding of past and poorly documented GLOF events in remote, data-scarce high mountain environments.

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Glaciers, glacial lakes and glacial lake outburst floods in the Mount Everest region, Nepal

Annals of Glaciology ◽

10.3189/172756410790595895 ◽

2009 ◽

Vol 50 (53) ◽

pp. 81-86 ◽

Cited By ~ 138

Author(s):

Samjwal Ratna Bajracharya ◽

Pradeep Mool

Keyword(s):

Average Rate ◽

Glacial Lake ◽

High Mountain ◽

Glacial Lakes ◽

Mount Everest ◽

The Past ◽

Outburst Floods ◽

Glacial Lake Outburst Floods ◽

Himalayan Glaciers ◽

Recent Climate

AbstractRecent climate changes have had a significant impact on the high-mountain glacial environment. Rapid melting of glaciers has resulted in the formation and expansion of moraine-dammed lakes, creating a potential danger from glacial lake outburst floods (GLOFs). Most lakes have formed during the second half of the 20th century. Glaciers in the Mount Everest (Sagamartha) region, Nepal, are retreating at an average rate of 10–59 ma–1. From 1976 to 2000, Lumding and Imja Glaciers retreated 42 and 34 ma–1, respectively, a rate that increased to 74 ma–1 for both glaciers from 2000 to 2007. During the past decade, Himalayan glaciers have generally been shrinking and retreating faster while moraine-dammed lakes have been proliferating. Although the number of lakes above 3500 m a.s.l. has decreased, the overall area of moraine-dammed lakes is increasing. Understanding the behaviour of glaciers and glacial lakes is a vital aspect of GLOF disaster management.

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Can a dam type of an alpine lake be derived from lake geometry? A negative result

Journal of Mountain Science ◽

10.1007/s11629-020-6003-9 ◽

2021 ◽

Vol 18 (3) ◽

pp. 614-621

Author(s):

Adam Emmer ◽

Vojtěch Cuřín

Keyword(s):

Extreme Values ◽

High Mountain ◽

Dam Breach ◽

Geometrical Properties ◽

Outburst Floods ◽

Glacial Lake Outburst Floods ◽

Hazard And Risk ◽

Dammed Lake ◽

Dam Overtopping ◽

Qualitative Characteristics

AbstractGlacial lake outburst floods (GLOFs) represent one of the most serious hazard and risk in deglaciating high mountain regions worldwide and the need for GLOF hazard and risk assessment is apparent. As a consequence, numerous region- and nation-wide GLOF assessment studies have been published recently. These studies cover large areas and consider hundreds to thousands of lakes, prioritizing the hazard posed by them. Clearly, certain simplification is required for executing such studies, often resulting in neglecting qualitative characteristics which would need manual assignment. Different lake dam types (e.g., bedrock-dammed, moraine-dammed) are often not distinguished, despite they control GLOF mechanism (dam overtopping/dam breach) and thus GLOF magnitude. In this study, we explore the potential of easily measurable quantitative characteristics and four ratios to approximate the lake dam type. Our dataset of 851 lakes of the Cordillera Blanca suggests that while variances and means of these characteristics of individual lake types differ significantly (F-test, t-test), value distribution of different geometrical properties can’t be used for the originally proposed purpose along the spectra. The only promising results are obtained for extreme values (selected bins) of the ratios. For instance, the low width to length ratio indicates likely moraine-dammed lake while the high value of ratio indicating round-shape of the lake indicates increased likelihood of bedrock-dammed lake. Overall, we report a negative result of our experiment since there are negligible differences of relative frequencies in most of the bins along the spectra.

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Glacial Lake Outburst Floods (GLOFs) in the Cordillera Huayhuash, Peru: Historic Events and Current Susceptibility

Water ◽

10.3390/w12102664 ◽

2020 ◽

Vol 12 (10) ◽

pp. 2664

Author(s):

Jan Baťka ◽

Vít Vilímek ◽

Eva Štefanová ◽

Simon J. Cook ◽

Adam Emmer

Keyword(s):

Ice Age ◽

Glacial Lake ◽

Dam Breach ◽

Hazard Management ◽

Lake Evolution ◽

Outburst Floods ◽

Glacial Lake Outburst Floods ◽

High Resolution Satellite Images ◽

Glacier Ice ◽

Dam Overtopping

The aim of this paper is to create a glacial lake inventory for the Cordillera Huayhuash in Peru and to evaluate the susceptibility of lakes to the generation of glacial lake outburst floods (GLOFs). Using high-resolution satellite images, we undertook qualitative and quantitative analysis of lake type, characteristics and distribution, and placed our findings within the context of existing Peru-wide lake inventories. We also mapped and analyzed past GLOFs, revealing a total of 10 GLOFs and 4 ambiguous events, most of which have not been reported before. We found that past GLOFs usually occurred as a result of moraine dam breach during the proglacial stage of lake evolution. Further, we used our lake inventory to evaluate GLOF susceptibility of all lakes larger than 20,000 m2. Of 46 evaluated lakes, only two lakes (Lake Tsacra and Lake W014) are currently susceptible to generating a GLOF, which would most likely be through dam overtopping resulting from a flood originating in smaller lakes located upstream. The future perspectives of lake evolution and implications for GLOF hazard management are discussed in light of the post-Little Ice Age glacier ice loss as well as in the context of extensive related research undertaken in the nearby Cordillera Blanca.

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