Preprints
https://doi.org/10.5194/egusphere-2025-4136
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/egusphere-2025-4136
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
13 Oct 2025
| 13 Oct 2025
Status: this preprint is open for discussion and under review for Natural Hazards and Earth System Sciences (NHESS).
Brief communication: Towards defining the worst-case breach scenarios and potential flood volumes for moraine-dammed lake outbursts
Abstract. Moraine dam failures are the main source of catastrophic glacial lake outburst floods (GLOFs). The effective GLOF disaster risk management requires reliable identification of areas at risk. While predictive outburst flood modelling benefits from advancing tools and computational capacities, some of the fundamental considerations remain poorly addressed. Among them, the outburst flood scenarios are essential yet often oversimplified input for modelling. Here we present novel methodology which enables the estimation of a maximum breach depth and so the calculation of potential flood volume (PFV), with the key parameter being the slope of the breached channel (α) derived from past events.
How to cite. Emmer, A., Sattar, A., and Hrebrina, J.: Brief communication: Towards defining the worst-case breach scenarios and potential flood volumes for moraine-dammed lake outbursts, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2025-4136, 2025.
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- CC1: 'Comment on egusphere-2025-4136', Koji Fujita, 20 Nov 2025 reply
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Department of Geography and Regional Science, University of Graz, 8010 Graz, Austria
Ashim Sattar
School of Earth, Ocean and Climate Sciences, Indian Institute of Technology Bhubaneswar, Bhubaneswar, Odisha, India
Jan Hrebrina
Department of Civil and Environmental Engineering, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
Short summary
Glacial lake outburst floods (GLOFs) are major concern in high mountain regions across the globe and effective disaster risk management requires predictive modelling which needs various input data including potential flood volume. Building on the analysis of breached channels of largest documented GLOFs originating from moraine dam failures, we present new methodology that estimates maximum breach depth and so potential flood volumes of moraine-dammed lake outbursts.
Glacial lake outburst floods (GLOFs) are major concern in high mountain regions across the globe...
Dear authors,
This study estimates the potential flood volume (PFV) of glacial lakes from the angle of the post-GLOF flow path. Although it does not evaluate the outburst potential itself, I believe it provides useful information. As a researcher who has conducted similar prior research, I offer several comments that I hope will be helpful.
The fact that the angle of the post-GLOF flow path is small was shown in Figure 6 of Fujita et al. (2013), so I would appreciate it if this could also be mentioned in the manuscript. The difference in PFV estimates ultimately stems from the choice of threshold: 10° in Fujita et al. (2013) and 3° in this study, so it would be good to refer to this point in the discussion.
I believe the Supplement figure represents an important result of this study, so it should be included in the main manuscript. It should also be discussed what characteristics glacial lakes with large angles maintained even after outburst tend to have.
I have some objections regarding the method shown in Figure 1D and Equations 1 & 2. What can actually be measured from satellite data is the “horizontal distance”, not the “slope distance”; therefore, “d” should be treated as the horizontal distance, and the angle should be calculated using the arctangent (Equation 1). In addition, Equation 2 should be computed using the tangent.
In estimating the PFV shown in Figure 2, the calculations use the moraine crest, but glacial lakes are not necessarily filled with water up to the top of the moraine. Therefore, it would be better to use the lakeshore, which is easier to identify in satellite imagery.
The moraine toe boundary is not clearly identifiable for all glacial lakes. The impact of uncertainty in determining the toe position on the PFV should be evaluated.
Regarding the PFV re-evaluated in Table 1, Fujita et al. (2013) assessed PFV for many glacial lakes and also provided their location information in the Supplement. Therefore, PFV should be evaluated for a larger number of glacial lakes.