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

Westoby, Matthew; Brasington, James; Glasser, Neil F.; Hambrey, Michael J.; Reynolds, John M.; Hassan, Mohamed; Lowe, Alfred S.

doi:10.5194/esurf-3-171-2015

Cited by 41 publications

(27 citation statements)

References 111 publications

(174 reference statements)

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“…The assumption of instantaneous dam failure, such as we have made here, may be appropriate for examining flood hazard and hydraulics downstream because it represents a worse-case scenario of breaching and provides maximum estimates for peak discharge and flow depth downstream. However, this treatment of the dam failure could be improved with more sophisticated empirical dam breaching models (e.g., Froehlich, 2016;Westoby et al, 2015), particularly if parameters related to the geometry and composition of the dam are known. The precise timescale of the Yigong dam failure is unclear (Delaney & Evans, 2015;Shang et al, 2003;Zhu et al, 2003) and likely <1 hr, but future simulations could investigate the effects of different breaching rates and dam parameters on downstream flow conditions.…”

Section: 1029/2018jf004778mentioning

confidence: 99%

The Geomorphic Impact of Outburst Floods: Integrating Observations and Numerical Simulations of the 2000 Yigong Flood, Eastern Himalaya

2019

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Outburst floods in mountainous landscapes traverse complex topography and interact with the channel and valley walls, producing intense flow hydraulics that drive geomorphic change and impact people and infrastructure. Evidence of modern and ancient outburst floods is scattered around the eastern Himalaya, but hydraulics related to these geomorphic features are uncharacterized, limiting our understanding of the role of large floods in long‐term evolution of the region. Here we combine remote and field observations of the 2000 Yigong River landslide‐dam outburst flood with 2‐D numerical flood simulations using the software GeoClaw. Modeling results agree with field evidence to the extent that we judge the simulated hydraulics to be relevant to flood hazard and geomorphic investigations. Results show that the hydraulics of outburst floods through rugged topography differ from those expected for nonflood flows, in magnitude and in the spatial patterns of flow speed, direction, and shear stress. The flood produced sustained high bed shear stresses capable of plucking meter‐scale blocks immediately downstream of breach, in the steep Tsangpo Gorge, and in isolated locations associated with valley constrictions. Simulated shear stresses suggest that outburst floods deposited numerous kilometer‐scale boulder bars observed along the flood pathway, armoring the bed, increasing channel roughness, and inhibiting incision in locations that would not be predicted for nonflood flows. Our findings highlight the potential for different magnitude flows to promote not only different amounts, but also different patterns of bedrock erosion, with implications for the role of prehistoric megafloods in the topographic evolution of the eastern Himalaya.

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Section: 1029/2018jf004778mentioning

confidence: 99%

The Geomorphic Impact of Outburst Floods: Integrating Observations and Numerical Simulations of the 2000 Yigong Flood, Eastern Himalaya

2019

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“…Dig Tsho (86 • 35.1 E, 27 • 52.5 N, 4365.9 m a.s.l.) has been extensively studied and used as a site to assess and improve GLOF models (Cenderelli and Wohl, 2001;Bajracharya et al, 2007;Westoby et al, 2014Westoby et al, , 2015Watson et al, 2015). Chamlang South Tsho (86 • 57.5 E,27 • 45.3 N,4951.8 m a.s.l.)…”

Section: Study Areamentioning

confidence: 99%

“…Methods have been developed to characterize the hazard and risk associated with glacial lakes in Cordillera Blanca (Reynolds, 2003;Hegglin and Huggel, 2008;Vilímek, 2013, 2014), New Zealand (Allen et al, 2009), North America (Clague and Evans, 2000;O'Connor et al, 2001;McKillop and Clague, 2007a, b), the Swiss Alps (Huggel et al, 2004b;Nussbaumer et al, 2014), the Himalaya (Wang et al, 2008(Wang et al, , 2012ICIMOD, 2011;Fujita et al, 2013;Worni et al, 2013), the Tibetan Plateau (Wang et al, 2011), and other parts of high-mountain Asia (Bolch et al, 2011;Mergili and Schneider, 2011). These methods vary considerably based on the parameters considered, the level of importance placed upon each parameter, the amount and type of required input data, their ability to be transferred to other regions, and their levels of objectivity.…”

Section: Introductionmentioning

confidence: 99%

A new remote hazard and risk assessment framework for glacial lakes in the Nepal Himalaya

Rounce

McKinney

Lala

et al. 2016

Hydrol. Earth Syst. Sci.

100

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Abstract. Glacial lake outburst floods (GLOFs) pose a significant threat to downstream communities and infrastructure due to their potential to rapidly unleash stored lake water. The most common triggers of these GLOFs are mass movement entering the lake and/or the self-destruction of the terminal moraine due to hydrostatic pressures or a buried ice core. This study initially uses previous qualitative and quantitative assessments to understand the hazards associated with eight glacial lakes in the Nepal Himalaya that are widely considered to be highly dangerous. The previous assessments yield conflicting classifications with respect to each glacial lake, which spurred the development of a new holistic, reproducible, and objective approach based solely on remotely sensed data. This remote hazard assessment analyzes mass movement entering the lake, the stability of the moraine, and lake growth in conjunction with a geometric GLOF to determine the downstream impacts such that the present and future risk associated with each glacial lake may be quantified. The new approach is developed within a hazard, risk, and management action framework with the aim that this remote assessment may guide future field campaigns, modeling efforts, and ultimately risk-mitigation strategies. The remote assessment was found to provide valuable information regarding the hazards faced by each glacial lake and results were discussed within the context of the current state of knowledge to help guide future efforts.

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“…Determining outflow volume, breach depth, and breach rate usually requires detailed field surveys to constrain the lake bathymetry and dam properties; clearly this is impossible given the setting and number of lakes in our study. Instead, we explicitly quantify these uncertainties by sampling from probability distributions that we derived from published data (Huggel et al 2002, O'Connor and Beebee 2009, Sakai 2012) using a Monte-Carlo simulation (Westoby et al 2014b(Westoby et al , 2015) (see supplementary information). Our probabilistic model (figures S1-3, table S1) computes for each lake 100 000 dam-breach simulations with differing values of corresponding peak discharge and outburst volume (Walder and O'Connor 1997).…”

Section: Methodsmentioning

confidence: 99%

Uncertainty in the Himalayan energy–water nexus: estimating regional exposure to glacial lake outburst floods

Schwanghart

Worni

Huggel

et al. 2016

Environ. Res. Lett.

116

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Himalayan water resources attract a rapidly growing number of hydroelectric power projects (HPP) to satisfy Asia's soaring energy demands. Yet HPP operating or planned in steep, glacier-fed mountain rivers face hazards of glacial lake outburst floods (GLOFs) that can damage hydropower infrastructure, alter water and sediment yields, and compromise livelihoods downstream. Detailed appraisals of such GLOF hazards are limited to case studies, however, and a more comprehensive, systematic analysis remains elusive. To this end we estimate the regional exposure of 257 Himalayan HPP to GLOFs, using a flood-wave propagation model fed by Monte Carlo-derived outburst volumes of >2300 glacial lakes. We interpret the spread of thus modeled peak discharges as a predictive uncertainty that arises mainly from outburst volumes and dam-breach rates that are difficult to assess before dams fail. With 66% of sampled HPP are on potential GLOF tracks, up to one third of these HPP could experience GLOF discharges well above local design floods, as hydropower development continues to seek higher sites closer to glacial lakes. We compute that this systematic push of HPP into headwaters effectively doubles the uncertainty about GLOF peak discharge in these locations. Peak discharges farther downstream, in contrast, are easier to predict because GLOF waves attenuate rapidly. Considering this systematic pattern of regional GLOF exposure might aid the site selection of future Himalayan HPP. Our method can augment, and help to regularly update, current hazard assessments, given that global warming is likely changing the number and size of Himalayan meltwater lakes.

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

Cited by 41 publications

References 111 publications

The Geomorphic Impact of Outburst Floods: Integrating Observations and Numerical Simulations of the 2000 Yigong Flood, Eastern Himalaya

The Geomorphic Impact of Outburst Floods: Integrating Observations and Numerical Simulations of the 2000 Yigong Flood, Eastern Himalaya

A new remote hazard and risk assessment framework for glacial lakes in the Nepal Himalaya

Uncertainty in the Himalayan energy–water nexus: estimating regional exposure to glacial lake outburst floods

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