the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 09 Jan 2025
The Parraguirre ice-rock avalanche 1987, semi-arid Andes, Chile – A holistic revision
Abstract. Chile is particularly exposed to mountain hazards along the Andean Cordillera. Impact and frequency of devastating debris-flows is expected to increase in the future under climatic warming and urban expansion. To inform monitoring, mitigation and adaptation measures, it is crucial to understand the characteristics of past events in this region. The Parraguirre rock avalanche of November 29, 1987 is a prominent example as it developed into a devastating debris flow reaching 50-km down-valley causing severe damage and loss of human lives. Its destructive power is related to the large water volume involved. The origin of this water is largely unknown – so is the initial trigger volume and the total mass transfer down valley. We therefore retrace the past event using new findings from remote sensing, climate and hydrological records as well as process-based modelling. Important corrections are at order. We find a trigger volume of 17.0 ± 1.4·106 m3 and a total fluid flood volume of 16.0·106 m3. The solid mass transfer out of the Parraguirre catchment amounts to 38.1 ± 15.2·106 m3. The high water content cannot be explained by entrainment of soil water and snow cover alone but requires substantial contribution from glacier ice. Furthermore, our simulations corroborate the damming hypothesis of Río Colorado and thereby reconcile the observed wave pulses, arrival times and run-out distance. Apart from the geo-tectonic pre-conditioning, we forward the Parraguirre rock avalanche as a meteorological compound event. The reason is that the spring of 1987 was outstanding in terms of the snowpack height, which preconditioned high snow-melt rates during particularly anomalous warm days at the end of November. Such pre-conditioning is readily accountable in monitoring and early warning procedures for mountain hazards.
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RC1: 'Comment on egusphere-2024-3103', Anonymous Referee #1, 21 Apr 2025
General Comments:
This manuscript offers a thorough and insightful re-evaluation of the 1987 Parraguirre ice-rock avalanche using a multidisciplinary approach that combines modern remote sensing, climate reanalysis, hydrological data, and process-based modeling. The authors make a compelling case for interpreting the event as a meteorological compound hazard and provide improved volume estimates and simulation-based evidence supporting the damming hypothesis.
The study is scientifically sound, well-written, and rich in detail. It contributes valuable insights for understanding high-mountain hazards under changing climatic conditions. I recommend minor revisions to improve the structure and clarity of some sections, particularly in the result and discussion.
Specific Comments:
- The literature review is very detailed but could be condensed slightly. Emphasize the knowledge gaps and novelty of this study earlier in the section to help guide the reader.
- In Section 5.4, the process of filtering acceptable simulations is repeated and could be streamlined. Combine or summarize the filtering logic and present the retained ensemble clearly with a count and justification.
- In Section 6.2, The discussion on possible sources of flood water is technically rich but dense. Structure it into separate sub-sections or use bullet points for snowmelt, glacier ice, and soil water. Consider adding a bar chart or conceptual diagram to visually support the breakdown.
- Some figures (e.g., Figs. 6 - 8) are slightly difficult to interpret due to small text and dense legend content. Increase font sizes and simplify legends where possible for readability, especially in grayscale.
- In Conclusions, add one or two sentences on how the results can inform future landslide hazard assessments or early warning systems in similar mountainous regions.
Citation: https://doi.org/10.5194/egusphere-2024-3103-RC1 - AC1: 'Reply on RC1', Johannes J. Fürst, 27 May 2025
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RC2: 'Comment on egusphere-2024-3103', Anonymous Referee #2, 24 Apr 2025
Thank you very much for the opportunity to review the manuscript titled “The Parraguirre Ice-Rock Avalanche 1987, Semi-Arid Andes, Chile—A Holistic Revision.”
This well-written manuscript offers a compelling and thorough reevaluation of a significant disaster event that occurred over three decades ago. The authors have effectively resurrected this event through the lens of modern analytical techniques and technologies, which were unavailable at the time of the original occurrence. By integrating contemporary methods, this study helps bridge knowledge gaps and contributes meaningfully to disaster science by reassessing historical events with improved precision and understanding.
I commend the authors for their comprehensive approach; however, I suggest a few minor revisions to enhance the manuscript's clarity and accessibility:
-
Abstract: Please briefly mention your methodological approach in the abstract to better inform readers about the basis of your analysis.
-
Manuscript Length and Precision: The manuscript is quite extensive, and at times, overly descriptive, which may hinder reader engagement.
-
The data section could be more concise while still retaining essential information.
-
The discussion, though critical, becomes lengthy and should be streamlined to maintain focus and readability.
-
The conclusion can be more impactful if limited to two well-crafted paragraphs summarizing key findings and implications.
-
Overall, this is a valuable and timely contribution, and with these refinements, the manuscript will become even more effective and reader-friendly.
Citation: https://doi.org/10.5194/egusphere-2024-3103-RC2 - AC3: 'Reply on RC2', Johannes J. Fürst, 27 May 2025
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RC3: 'Comment on egusphere-2024-3103', Anonymous Referee #3, 27 Apr 2025
Reviewer’s comments
Ref: manuscript egusphere-2024-3103
Title: The Parraguirre ice-rock avalanche 1987, semi-arid Andes, Chile -A holistic revision
General Comments:
In this study, the authors simulated the 1987 Parraguirre Debris flow by using existing records with hydro-climatological data, remote sensing observations, and process-based modeling. For simulation, the r.avaflow (open access software) has been used. Their simulated model has been validated with existing results of previous studies and field observations. The research is interesting and important to predict the future ice-rock avalanche for global warming due to climate change, but not a novel one.
Specific Comments:
- There are grammatical errors and typos (such as line 2 (Abstract): instead of ‘is’ here will be ‘are’). The authors should go through a thorough editing of the manuscript to correct grammatical errors and improve the readability of the paper, using a professional English editor as appropriate.
- The 30-m resolution Digital Elevation Models (DEM) generated from a 1:50,000 scale topographic map and aerial photographs have been used in this study. The volume of debris and water calculations of the 1987 avalanche using re-registering (resampling) of a 30-m resolution DEM is not accurate and precise. Therefore, the volume of debris and water is much higher than in the previous studies. Describe this limitation in the discussion section.
- The weather stations are sparsely distributed in the study areas. The weather parameters, such as temperature, precipitation taken from 40 to 50 km away from the areas where the volume of melt ice was calculated. The temperature within 40/50 km may vary several degrees. Therefore, this limitation should be explained in the discussion section.
- This type of limitation is also observed in the hydrological data; the limitation of the hydrological data (discharge) should be explained in the discussion section.
- The caption of the figure should be numbered first, and then write the text of the caption, such as (a) Southern South America and (b) inset of the Metropolitan
- Technically, I think the method described in the manuscript is sound, but not innovative.
Decision: Major revision
- AC2: 'Reply on RC3', Johannes J. Fürst, 27 May 2025
Status: closed
-
RC1: 'Comment on egusphere-2024-3103', Anonymous Referee #1, 21 Apr 2025
General Comments:
This manuscript offers a thorough and insightful re-evaluation of the 1987 Parraguirre ice-rock avalanche using a multidisciplinary approach that combines modern remote sensing, climate reanalysis, hydrological data, and process-based modeling. The authors make a compelling case for interpreting the event as a meteorological compound hazard and provide improved volume estimates and simulation-based evidence supporting the damming hypothesis.
The study is scientifically sound, well-written, and rich in detail. It contributes valuable insights for understanding high-mountain hazards under changing climatic conditions. I recommend minor revisions to improve the structure and clarity of some sections, particularly in the result and discussion.
Specific Comments:
- The literature review is very detailed but could be condensed slightly. Emphasize the knowledge gaps and novelty of this study earlier in the section to help guide the reader.
- In Section 5.4, the process of filtering acceptable simulations is repeated and could be streamlined. Combine or summarize the filtering logic and present the retained ensemble clearly with a count and justification.
- In Section 6.2, The discussion on possible sources of flood water is technically rich but dense. Structure it into separate sub-sections or use bullet points for snowmelt, glacier ice, and soil water. Consider adding a bar chart or conceptual diagram to visually support the breakdown.
- Some figures (e.g., Figs. 6 - 8) are slightly difficult to interpret due to small text and dense legend content. Increase font sizes and simplify legends where possible for readability, especially in grayscale.
- In Conclusions, add one or two sentences on how the results can inform future landslide hazard assessments or early warning systems in similar mountainous regions.
Citation: https://doi.org/10.5194/egusphere-2024-3103-RC1 - AC1: 'Reply on RC1', Johannes J. Fürst, 27 May 2025
-
RC2: 'Comment on egusphere-2024-3103', Anonymous Referee #2, 24 Apr 2025
Thank you very much for the opportunity to review the manuscript titled “The Parraguirre Ice-Rock Avalanche 1987, Semi-Arid Andes, Chile—A Holistic Revision.”
This well-written manuscript offers a compelling and thorough reevaluation of a significant disaster event that occurred over three decades ago. The authors have effectively resurrected this event through the lens of modern analytical techniques and technologies, which were unavailable at the time of the original occurrence. By integrating contemporary methods, this study helps bridge knowledge gaps and contributes meaningfully to disaster science by reassessing historical events with improved precision and understanding.
I commend the authors for their comprehensive approach; however, I suggest a few minor revisions to enhance the manuscript's clarity and accessibility:
-
Abstract: Please briefly mention your methodological approach in the abstract to better inform readers about the basis of your analysis.
-
Manuscript Length and Precision: The manuscript is quite extensive, and at times, overly descriptive, which may hinder reader engagement.
-
The data section could be more concise while still retaining essential information.
-
The discussion, though critical, becomes lengthy and should be streamlined to maintain focus and readability.
-
The conclusion can be more impactful if limited to two well-crafted paragraphs summarizing key findings and implications.
-
Overall, this is a valuable and timely contribution, and with these refinements, the manuscript will become even more effective and reader-friendly.
Citation: https://doi.org/10.5194/egusphere-2024-3103-RC2 - AC3: 'Reply on RC2', Johannes J. Fürst, 27 May 2025
-
-
RC3: 'Comment on egusphere-2024-3103', Anonymous Referee #3, 27 Apr 2025
Reviewer’s comments
Ref: manuscript egusphere-2024-3103
Title: The Parraguirre ice-rock avalanche 1987, semi-arid Andes, Chile -A holistic revision
General Comments:
In this study, the authors simulated the 1987 Parraguirre Debris flow by using existing records with hydro-climatological data, remote sensing observations, and process-based modeling. For simulation, the r.avaflow (open access software) has been used. Their simulated model has been validated with existing results of previous studies and field observations. The research is interesting and important to predict the future ice-rock avalanche for global warming due to climate change, but not a novel one.
Specific Comments:
- There are grammatical errors and typos (such as line 2 (Abstract): instead of ‘is’ here will be ‘are’). The authors should go through a thorough editing of the manuscript to correct grammatical errors and improve the readability of the paper, using a professional English editor as appropriate.
- The 30-m resolution Digital Elevation Models (DEM) generated from a 1:50,000 scale topographic map and aerial photographs have been used in this study. The volume of debris and water calculations of the 1987 avalanche using re-registering (resampling) of a 30-m resolution DEM is not accurate and precise. Therefore, the volume of debris and water is much higher than in the previous studies. Describe this limitation in the discussion section.
- The weather stations are sparsely distributed in the study areas. The weather parameters, such as temperature, precipitation taken from 40 to 50 km away from the areas where the volume of melt ice was calculated. The temperature within 40/50 km may vary several degrees. Therefore, this limitation should be explained in the discussion section.
- This type of limitation is also observed in the hydrological data; the limitation of the hydrological data (discharge) should be explained in the discussion section.
- The caption of the figure should be numbered first, and then write the text of the caption, such as (a) Southern South America and (b) inset of the Metropolitan
- Technically, I think the method described in the manuscript is sound, but not innovative.
Decision: Major revision
- AC2: 'Reply on RC3', Johannes J. Fürst, 27 May 2025
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