the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 11 Feb 2026
Reconstruction of the 1989 Laguna Del Cerro Largo GLOF: an Interdisciplinary Understanding of GLOF Impacts
Abstract. The March 16, 1989, glacial lake outburst flood (GLOF) from Laguna del Cerro Largo in Valle Soler, Aysén, Chile, is one of the largest recent moraine-dammed GLOFs in the region. This interdisciplinary approach reconstructs the GLOF downstream impacts using HEC-RAS 2D and GeoClaw from witness accounts. Model results are then validated through field analysis of sediment deposition, dendrogeomorphic surveys, radiocarbon dating. Sediment cores reveal distinct clastic layers attributable to the 1989 event and evidence of an earlier outburst flood from the adjacent Laguna Turbio, dated circa 125 ybp. The model results also indicate a substantially higher peak discharge than official reports, impacting subsequent disaster policy decades later. While dendrogeomorphic sampling was hindered by fungal decay in Nothofagus species, the findings highlight both the potential and limitations of interdisciplinary reconstructions of GLOF events in remote, data-scarce environments.
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RC1: 'Comment on egusphere-2025-5791', Anonymous Referee #1, 04 Mar 2026
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AC1: 'Reply on RC1', Jonathan Burton, 13 Mar 2026
Thank you for your insight for this article. I appreciate your encouraging comments and in-depth review. I look forward to taking this feedback into account for future drafts.
For specific comments:
1) This is a great suggestion to further detail which data were used as input and which were independent constraints. I think a figure flowchart would be an excellent and efficient addition to the manuscript.
2) This is a consideration that I was looking into in previous work. I have not tried to generate a DEM from trimetrogon imagery and ultimately decided that the magnitude of the event supersedes the level of uncertainty from a DEM difference, as the flood had likely evolved to a more newtonian fluid at the analyzed stretches. I think that, as you suggested, a short discussion of DEM uncertainty would certainly be merited, and will be included in the manuscript.
3) Thank you for your feedback here. To be honest, the original draft had a much more detailed description of the information you indicated in your comment, but ultimately was scraped for the necessity of brevity. However, it does seem like I can and should address your concerns with a careful edit to respond to your questions. I will add a short description to incorporate your comments, but will describe our process briefly: We were limited by the duration of our field campaign and opted for a sample of 50. We sought out trees that had clear indications of disturbances, ie scares, scratches, etc. Additionally, we were looking for trees that were old enough to have likely been impacted by the flood. We found several trees that had scars and other disturbances, (I'd have to look at the numbers specifically) but the samples of those did not penetrate enough to capture pre-1989 growth. Generally, we followed sampling methods established in Gorsic et al 2025 and Ballesteros-Canovas 2015, trying to get one control sample and one sample on the disturbance for disturbance impacted trees. For the general sampling of visibly unaffected trees, (looking here for variations of growth rings), we selected trees which were higher than interannual flood plains to limit impacts from recent non-glof flooding, yet within the nominally affected zone of 4-8 meters above the river. In the manuscript I have several pictures of physical markers which maybe I didn't describe as thoroughly as I could have, with residual woody debris, scars, and remnant deposition in tree canopy. I will better link these observations to the model results, as you've suggested.
4) I think this is a huge consideration, thanks for bringing this up. I think certainly this has an impact on the modeling results, and merits discussion. Such sediment-rich flood waves are often described as hyperconcentrated flows occupying the continuum between clear-water floods and debris flows, and my guess is that much of the initial flood energy was dissipated at the 90° turn upstream, seen by the immense sand and gravel deposition upstream of that corner, such that the downstream flood was closer to a clear-water flood than the upper reaches with large boulders mobilized. I will add an additional paragraph with considerations.
5) We thank the reviewer for this crucial input. I have another publication in-review that is an in-depth analysis of regional GLOF risk policy that I can pilfer some insights for this topic. In short, prior to our work, the largest GLOF Qpeak were those that came from Colonia, and the new cycle emanating from HPN4 near Steffan. These GLOF discharges seem to attenuate due to the impounding glacier that extends drainage to over the course of several days, with peak discharges near 5k m3. I collaborated with the DGA to model HPN4 and this is also in-review. The balance between low-probability / high-impact of moraine dammed glacial lakes aren't actively mitigated for because of the prior underestimate of potential magnitudes, and thus have important consequences for the scope of DRR work in the area.
We thank the author again for the valuable insights and comments, and look forward to incorporating these edits and further discussion.
Citation: https://doi.org/10.5194/egusphere-2025-5791-AC1
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AC1: 'Reply on RC1', Jonathan Burton, 13 Mar 2026
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RC2: 'Comment on egusphere-2025-5791', Loic Piret, 15 May 2026
This manuscript investigates the 1989 GLOF that occurred on the eastern side of the NPI, in Valle Soler, Chilean Patagonia. It does so by combining multiple diverse datasets and a model approach. The datasets include sediment cores (Russian peat corer), dendrological evidence, two radiocarbon dates, UAV-based DEM, and witness accounts which are used as input parameters for the two different hydrological models. The authors present new convincing findings regarding the flood dynamics and the triggering mechanism of the GLOF compared to what was previously reported about this particular GLOF by Hauser (1993).
In general, this work is a substantial contribution to the scientific literature on GLOFs in Patagonia and their physical and human impact. It was a pleasure to read this manuscript (though I do have a comment on the writing style - see below), and I believe that with moderate revision, this article will be ready for publication soon.
I hope these comments help improve the manuscript.With kind regards,
Loic PiretGeneral comments:
(1) Datasets not integrated in the discussion: The authors have created and compiled an extensive and diverse dataset in this data-sparse region. The discussion section focuses on the findings based on the model output and the witness interviews. However, not all results are integrated in the discussion:
Firstly, the UAV-derived DEM is announced in the abstract and introduction section and its creation is detailed in the methodology section. The UAV-derived output however does not seem to further appear in the manuscript. Please include these results (more explicitly) in the manuscript and how they helped understand the 1989 GLOF dynamics.
Secondly, the sediment cores are presented in the results but receive very little attention in the discussion. I'm left with the question of what the sediment analysis actually showed. The two clastic layers found in the cores are interpreted to represent the two GLOF's in the valley which occurred in the valley. But what can we tell about the sediment grain-size gradations, the core-to-core correlations and variability in thickness of the deposits between the sites? Is it not possible to get information about the flood energy, duration, and spatial extent of the flood using these sediment cores? This data can then be linked back to the hydrologic model outputs, which can then help validate (or challenge) the model outputs.
Thirdly, the abandonment of the dendrogeomorphologic dataset is disclosed honestly and it is important we mention such "failed" methods. However, at L325-340, some other (non-abandoned) findings are mentioned about where trunks were found but it is unclear what actually can be deduced from these findings. Finally, the Carbon-14 dating needs some revision and integration in the discussion as well (see also specific comments).
In short: The manuscript would benefit from a new more explicitly data-driven discussion section.(2) Writing style: The authors occasionally adopt an Americanized journalistic (and at times, anecdotal) tone rather than a rigorous, formal analytical tone which is considered more suited for a peer-reviewed scientific article. Though I enjoyed reading it, I'm unsure whether this writing style is 100% fitting for this format. Ultimately, I leave the decision on which writing styles are appropriate for this journal to the discretion of the editorial team. Some specific examples of the journalistic/anecdotal approach are noted by line number here: L78-80, L168-169, L255-258 (this is a particularly dramatic anecdotal passage), L413-414 (anecdotal).
Specific comments:
L80: The term "epistemological pluralism" (and, later in the manuscript at L421: "Epistemological Blind Spots") is quite heavy. I would suggest to either clarify what "epistemological pluralism" means or to refrain from using it. While this concept is valuable, the specialized terminology may form a barrier for non-native English-speaking scientists. I would encourage the use of slightly more accessible language.L233-237: Are these findings on the grain size based on your sediment core results or were they previously published in either Burton et al 2020 or Sincavage et al 2023 (this ref is not in reference list)? In case of the former: add them to the result section of the sediment cores. In case of the latter: it would be better to place this in the discussion section and compare with your own grain-size results from the sediment cores.
Section 3.3. (L284): The single C14 date shows that this top clastic layer is from the 1989 GLOF. However, can we be sure that this clastic layer is all deposited at once? Maybe there is sedimentological evidence pointing to a single-event deposit (downcore grain-size patterns for instance). It would make sense that this is a single deposit based on the context and witness accounts but independent evidence is preferred.
L289-294: Does the grain size only vary with distance downstream or is it also dependent on the specific geomorphic setting (e.g. low-lying, raised, near constriction, etc.)?
L347-349: "a counterintuitive coarsening of the grain size, before a gradual fining": It is unclear what is meant here. Is this a downstream trend in the valley? Is this a downcore grain-size trend? The Sincavage reference is not in the reference list.
At L354, it is mentioned that organic material was extracted from the clastic layer that is assumed to represent deposits of the 1989 GLOF. One date confirms this but the other result dates the sediment back to 1899 CE. This is confusing. Please show where the samples were taken on the sediment logs (figure 6) to clarify this.
L373-374: Please provide some appropriate examples of this triggering mechanism in similar situations to strengthen this idea. It is currently unclear where this idea came from. Furthermore, are there an other triggering mechanisms that should be considered?
The results regarding policy impacts appear overstated. While I acknowledge the limited discussion concerning policy-making in L72-73 and L416–420, the claims in these sections and at lines 460–461 require some more substantiation. The authors could provide references and insights into the existing relevant policy and legal frameworks to demonstrate how the 'original report' actually shaped the political landscape.
Tangential to this comment: If no such policy framework exists, or if it is outdated, a policy-brief should be written to inform the local policymakers!Fig 4 caption - L267: Could this be the other way around? The GeoClaw model shows the wave progression almost at a confluence at t=0.25, whereas the HEC-RAS 2D model shows a more limited wave progression at the same time. The wave in the GeoClaw model already reaches the rightmost edge of the study-area rectangle at t=1.5 hours, whereas in the HEC-RAS model, it only reaches the rightmost edge of the study-area rectangle at t=2.5 hours. Therefore, the HEC-RAS model shows a lag in wavefront propagation relative to the GeoClaw model.
Fig 6: Adding a dedicated depth scale instead of just the tape measure would improve the readability of this figure.Fig 9: Add the F14C value of the sample to the graph to show how you deduct an age of 1989 from this result. Also mention that technically, it could be from the 1950's but given the context, it is highly likely from 1989.
Technical corrections:
L49: I suggest to use the gender-neutral alternative "uncrewed" instead of unmanned. https://cordis.europa.eu/article/id/442165-not-unmanned-but-uncrewed
L80: Nightingale 2016 missing from reference list.
L237: Sincavage et al., 2023 missing from the reference list. Please verify that all references in the text are in the reference list and vice versa.
L256: Please explain what a coigue (i.e. Nothofagus dombeyi (?) ) is.
L289: Please explain Spanish words such as "campensino".
L355-356: "The 14C samples taken from the layer expected to have originated returned "modern age", ..." Currently, this sentence is grammatically incomplete. Is there a part missing from this sentence - particularly after "originated"? Also, should it be "fractional carbon of 1.1921; or "at" (as it is now).
L371: Add reference to the original report here.Citation: https://doi.org/10.5194/egusphere-2025-5791-RC2 -
AC2: 'Reply on RC2', Jonathan Burton, 13 Jun 2026
We kindly thank Dr. Loic Piret for his in-depth and constructive review of our paper. His comments bring a keen and familiar eye into some of the oversights of this paper, and we appreciate the time and effort spent in reviewing this manuscript. We will address his comments individually and outline how we will revise the paper.
General Comments:
1.1) This is a great point. One of the biggest contributions of this paper is presenting the output of the effort of generating the DEM from the drone. We are preparing a separate paper that is centrally focused on the drone imagery and geomorphologic features, which we don't want to detract from the other results in this paper, I can specify that the importance of the UAV derived DEM was used as input for the high-definition terrain through which the flood was routed. This can be described in more detail in the methods section.
1.2) Another helpful comment to spend more time in the discussions portion of the paper on this. I agree that I think I can do a better job tying this in to the results, and unpacking the significance in the discussion. My expertise is admittedly not in sediment hydraulics, and the secondary calculations are somewhat limited by the inaccessibility of the field. I did do a field calculation of grain sizes which I reported in the paper, and I can try to supplement the discussion with a first-order estimate of energy gradients related to the flood, as well as how this relates to the depositional environment and deposit thicknesses / spatial variability. I will address this concern by significantly supplementing the existing discussion section with additional analysis to assess the validation of model results.
1.3) This is very helpful feedback. I was intending to point out that these trunks are used as a conservative stage indicator of their deposits but this was unclear from the manuscript, and I will clarify this connection in the manuscript. I will additionally address and clarify the C-14 dating methods - specifics below.
2) Writing Style: I appreciate the candid comment about the writing style. As I I am an interdisciplinary scholar by training, it can be quite difficult to fully adapt my writing to the different fields of research, so this feedback is a helpful reorientation for this specific manuscript. That being said, I think one of the biggest contributions of this manuscript is the integration of unconventional data in order to generate meaningful scientific data - including witness testimony. I totally understand the comment that some of the wording could be presented in a less journalistic tone, and I'd be happy to implement that in a final manuscript. However, to undervalue the witness testimony as mere anecdote is - in my opinion - ultimately a disservice to the communities that we work in, and the science itself, as I demonstrate here the power that these histories can contribute to scientific knowledge generation. I will ultimately defer to the discretion of the editorial team, and appreciate the feedback from the reviewer.
L80 - Thank you for pointing this out. I think that I can convey the intended meaning in a way that is more accessible to all audiences.
L233 - This metric was previously published from Burton 2020 and will be moved to the discussion section to compare with my own grain-size results.
L284 - I appreciate the redirection here, and I take the reviewers point that my argument is slightly circular as is, basing this on the contextual and anecdotal evidence. In a revised manuscript, I will explain the sedimentological evidence internal to the core - namely that there was a sharp basal contact, with normal grading, and no internal organics.
L289 - Consistent with the reviewers comments in 1.2, the revised manuscript would receive more attention to the nuances of sediment deposition, with more analysis on the various contributors to differences found in the sediment deposits including - as Loic points out - geomorphic settings which influence flood turbidity and energy gradients.
L347 This wording will be clarified to indicated a downcore grain-size trend. The Sincavage citation will be added to the bibliography
L354 I can reword this to clarify the confusion here. The carbon sample was not taken from any of the existing russian auger cores, but was taken adjacent to one of the samples that can be used as a reference in figure 6. The second C-14 date was extracted from below a clastic lens which we interpreted as a deposition from the previous GLOF. I recognize that this point is similar to the previous comment made by the reviewer (L284) and I will be more explicit about the internal independent evidence here of the deposit's origin.
L373 - There are several papers that at least consider this a viable trigger mechanism - Irribarren 2014, Costa and Schuster 1988, and mass movements into a terminal lake more widely. These references will be added into the manuscript to substantial this idea.
Policy impacts - while not the main contribution of this article, I take the reviewers point that these claims can be better substantiated. I have another paper in review that takes this point more head on and I wanted to at least acknowledge the significance of those results, and I see that I can substantiate the few mentions of that better here. I think a quick sentence or two that, as the review points out, better grounds with within specific policy would help to evidence and clarify this point. Also, a helpful suggestion for the policy brief!
Fig 4 L267 - Thank you for pointing this out, you are 100% correct. I mixed up the models in the caption and it should be, as is reflected in the body of the text, that HEC-RAS shows a lag in the wavefront propagation relative to GeoCLAW.
Fig 6 Thank you for this suggestion, a revised manuscript would have a scale added to this graphic to indicate depth in a more legible format.
Fig 9 A great point, a revised manuscript will include an addition of the C14 levels and additional clarification of the deduction that we made from the context. We thank the reviewer for this suggestion.
Techincal Corrections
L49 - Thank you for bringing this to our attention. We strive for inclusive language and practices and this correction will be made.
L80 - This reference will be added to the bibliography
L237 - Thank you for pointing this out. I will review the references and bibliography to ensure all citations are included.
L256 - I thought I had introduced the trees in another part of the manuscript but it must have been cut during revision. Revisions will include the tree specie's scientific name.
L289 - I will include a translation of campesino, and all other Spanish words if present, in the text.
L355 - Thank you for finding this grammatical error. I will revise this sentence to be complete, and include the corrected 'fractional carbon of 1.1921
L371 - Reference to the original Hauser report will be added.
We would like to again thank Dr. Loic Piret for his contribution and meticulous review of our manuscript, and look forward to submitting a revised manuscript that reflect these changes. We hope that the above revisions will address the points made in this comment submission given the limitations that we have acknowledged from the data gathered.
Citation: https://doi.org/10.5194/egusphere-2025-5791-AC2
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AC2: 'Reply on RC2', Jonathan Burton, 13 Jun 2026
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Referee report on
“Reconstruction of the 1989 Laguna del Cerro Largo GLOF: an Interdisciplinary Understanding of GLOF Impacts”
General comments
This manuscript presents a comprehensive, interdisciplinary reconstruction of the 1989 Glacial Lake Outburst Flood (GLOF) in Valle Soler, Chile. By combining 2D hydrodynamic modelling with local witness accounts and field validation, the authors revisit an event for which instrumental data are scarce and historical estimates remain uncertain.
The study is significant because it challenges historical estimates of this event using modern hydrodynamic modelling and provides new insights into GLOF processes. The discrepancy identified between the ~2,000 m³ s⁻¹ estimate reported in the original study and the authors’ modelled peak discharge highlights a likely underestimation of GLOF hazards, with implications for regional hazard assessment.
The manuscript is generally well structured and clearly written. The compilation of modelling results, sedimentary evidence, and historical information represents a promising dataset. However, the integration between the different lines of evidence remains somewhat descriptive, and several methodological aspects would benefit from clarification regarding the robustness of the reconstruction.
Overall, the study has clear potential but requires minor revisions to strengthen methodological clarity and interdisciplinary synthesis.
Specific major comments
1. Framework and independence of evidence
The manuscript adopts a transdisciplinary approach combining modelling, field evidence, and witness testimonies. While this integration is a clear strength of the study, the analytical framework linking these datasets could be described more explicitly.
It would be helpful to clarify how the different datasets are used within the reconstruction (e.g. model inputs, validation constraints, contextual evidence). For instance, witness testimonies appear to provide both input parameters for the hydraulic simulations (e.g. timing or duration of the flood) and supporting evidence for the plausibility of the modelling results. The manuscript would benefit from clarifying which elements were used to parameterise the models and which were retained as independent validation constraints, in order to avoid potential circular reasoning.
A short conceptual workflow figure summarising how the different datasets contribute to the reconstruction could help clarify this methodological framework.
2. Pre-event topography and modelling
The hydraulic simulations are based on the Copernicus 30 m DEM acquired several decades after the 1989 event. The manuscript acknowledges that post-flood erosion and deposition may have modified channel geometry and flow pathways, but the implications for the hydraulic reconstruction are not discussed in detail.
Given that fluvio-glacial plains are particularly prone to channel migration, sediment redistribution, and morphological reorganisation, the DEM used may differ substantially from the pre-event terrain that controlled flood routing. The authors may wish to consider whether an approximate reconstruction of the pre-event topography could be attempted; for example, by adjusting DEM contours using georeferenced historical aerial imagery where available (e.g. trimetrogon photography is available for some periods in this region).
Alternatively, a short discussion of how DEM uncertainty may influence model results would strengthen the interpretation of the simulations.
3. "Vanishing Evidence" and Proxy Limitations
The manuscript reports that dendrogeomorphic sampling was hindered by fungal decay affecting Nothofagus species, which limited the usefulness of tree-ring evidence for reconstructing the 1989 event. Such preservation issues are well known in humid Patagonian environments. To help the authors enhance their discussion and better integrate these results, I offer the following comments:
4. Process interpretation versus modelling assumptions
The discussion suggests that the initial flood may have behaved as a dense, debris-flow-like slurry given the mobilisation of very large boulders. However, both modelling approaches are based on shallow-water, Newtonian flow assumptions. It could be interesting to briefly discuss how this interpretation of potentially debris-rich flow conditions relates to the modelling framework, and whether such processes could influence the reconstructed peak discharge or flow depths.
5. Contextualizing the revised peak discharge estimate
A key conclusion of the study is that peak discharge during the 1989 event may have been substantially higher than estimates initially reported in Hauser (1993). This is an important result, and the discussion could be strengthened by placing these revised estimates in a broader regional context.
For example, it may be useful to briefly compare the reconstructed discharge with other documented GLOF events in Patagonia or to clarify how such revised estimates might influence current interpretations of regional hazard.
Minor/Technical suggestions