Multitemporal Quantification of the Geomorphodynamics on a Slope within the Cratére Dolomieu—At the Piton de la Fournaise (La Réunion, Indian Ocean) Using Terrestrial LiDAR Data, Terrestrial Photographs, and Webcam Data

Round 1

Reviewer 1 Report (New Reviewer)

Comments and Suggestions for Authors

The paper, despite the authors' good intentions, is not a quantification of the geomorphodynamics of the inner flank of the volcano under study, but an application of integrated survey techniques to assess the topographical variations of areas that are only approximately delimited. What is lacking is an objective multi-temporal geomorphological map that represents not only the training areas, but also those around them. The authors are invited to supplement the images that now contain only approximate delineations of the areas of interest with appropriate cartographic representations. 

Apecific comments 

Title: What means "quantification"? the paper only describes the time step of the topographic variations. Please, could Authors use a term more appropriated?

 Line 16: "geomorphological evolution" instead "geomorphological development";

Line 16: "inner flank"instead the generic "part"

Line 20: crater activity? volcanic or denudational?

Line 23: What means "calculated into DEMs"? Can you better explain, shortly?

Line 23: See the above first comment in line 16.

Line 94: "pairs are" instead "pairsare"

Figure 3:What means stable areas? In my opinion, these areas are not stable, but only they are affected by different mechanisms at longer return time. 

 

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Can be improved

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report (New Reviewer)

Comments and Suggestions for Authors

The manuscript titled "Multitemporal quantification of the geomorphodynamics on a slope within the Dolomieu crater - Piton de la Fournaise (La Réunion, Indian Ocean) using terrestrial LiDAR data, terrestrial photographs, and webcam data" by Wegner et al is well-structured, addresses relevant topic in geoscience especially geomorphology, and presents a multi-modal remote sensing analysis using a combination of terrestrial LiDAR, photogrammetric images, and webcam data. However, several areas especially in method and results could be improved to enhance the paper's clarity, accuracy, and overall quality.

Major comments:

1.        Although the methods are well-detailed, some critical decisions made during data processing are not adequately justified. For example, the manuscript integrates data from different sources (LiDAR, photogrammetry, webcams), but the process of combining these datasets is complex and not entirely clear. The authors mention using Iterative Closest Point (ICP) adjustments but do not discuss how inconsistencies between datasets (e.g., differences in resolution and accuracy) were resolved. This integration process is critical for the study's validity and should be described in more depth, perhaps with a dedicated subsection.

2.        While the authors address errors through the Limit of Detection (LoD) calculation, the treatment of uncertainty remains superficial. For example, the manuscript should discuss how temporal gaps in data (e.g., missing webcam images) might influence the results and introduce uncertainty. Additionally, the implications of different LoD values across datasets are not fully explored.

3.        The results section contains detailed descriptions of surface changes in different zones, but the interpretation is somewhat limited. The authors tend to describe what happened without fully exploring why these changes occurred or what they mean for the broader understanding of slope evolution in volcanic settings. For example, the significant increase in rockfall activity between 2012 and 2014 (e.g Line 360-361) is mentioned but not adequately explained in relation to possible triggers (e.g., seismic activity, climatic factors).

4.        Line 378-379: The comparison with rockfall volumes from other studies (e.g., Volcán de Colima) is valuable but feels disconnected from the broader narrative. A more integrated comparison throughout the results would help contextualize these findings.

5.        Line 496-497: The statement about high activity due to recent crater formation is important but requires more supporting evidence. Consider referencing more studies on newly formed craters and their typical geomorphological behavior.

Additional suggestions:

Line 140-146: While the conditions necessary for LiDAR data acquisition are noted, it would be beneficial to briefly discuss how variations in these conditions (e.g., weather, light) impacted data quality or processing.

Line 279-297: The detailed breakdown of usable vs. discarded webcam photographs is useful but could be presented more effectively. A table summarizing the number of images per period and reasons for exclusion would reduce redundancy in the text.

Line 450-485: The discussion of the temporal specification of single events is insightful, but the connection between the qualitative observations (from webcam images) and quantitative measurements (surface changes) could be more explicit. A summary sentence tying these findings together would improve clarity.

Comments on the Quality of English Language

The writing is generally clear but occasionally becomes dense, particularly in the methodology and discussion sections. The authors should aim for more concise language, avoiding unnecessary repetition. Additionally, ensure that complex technical terms are defined when first introduced to improve accessibility for a broader audience.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors, 

I have mixed feelings after went through this manuscript. I was really satisfied with the methodological part. However, I have many issues with the introduction and discussion. I am not really sure the presented results can be used for what at its current form. The existing introduction should be shortened and should be completed by general information about the geomorphological evolution of craters/calderas. That would give a context for the readers.

Secondly, besides presenting a new methodological approach, I cannot see what has a high value of the results. The reader will not know what was the triggering for the erosion of caldera wall and we do not know that these quantities how comparable to processes in other volcanoes. For example, with the observed erosion rate, haw many hundreds of years need to reach the stabilisation of the caldera wall. It is suggested to compare it with other you crates or calderas (e.g., Miyakejima, Japan). I think without specific reason/aim the quantification of erosion (by itself) is not a sound research problem to be solved. 

Introduction;

I think the geomorphology, geology and climate of La Reunion is not comparable with the Alps. I would rewrite that section with using examples similar to the study area. 

Lines 78-89  is a good paragraph about the opportunities of using seismic data, but such a data was not used for the manuscript. 

Materials and Methods; 

Good, I have two extra suggestions; Please consider the using of InSAR data for monitoring the erosion. Secondly, grain size analysis of the deposits (through high resolution images) may give insights of the erosional/depositional processes. 

Results and discussion; 

I think the discussion need a major improvement, relying on comparison with other areas elsewhere and more about the triggering of the erosion of caldera wall. 

I am not sure why citation 49  have been used for comparison as that manuscript dealing with deposits of pyroclastic density currents. The process is much more important than the chemical composition of material. I would recommend to find angle of repose values for gravitation triggered mass movements and not from pyroclastic deposits. 

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

I have reviewed the manuscript titled "Multitemporal quantification of the geomorphodynamics on a slope within the Dolomieu crater -Piton de la Fournaise (La Réunion, Indian Ocean) using terrestrial LiDAR data, terrestrial photographs, and webcam data" with the following comments:

(1) Introduction: The introduction provides a good background and context for the study. It clearly outlines the research problem and the importance of the study. However, it could be further improved by providing a more detailed literature review on previous studies in the field and how this study builds upon previouswork(https://doi.org/10.1016/j.ijmst.2024.04.001;https://doi.org/10.1016/j.measurement.2023.114055; https://doi.org/10.1007/s00603-023-03274-7).

(2) Methodology: The methodology section is well-written and provides a clear description of the research design, data collection, and analysis methods. However, it could be slightly improved by providing more details on the data collection process, such as the number of images taken for each data source, the camera settings, and the fieldwork logistics. Additionally, it would be helpful to include a brief discussion on the challenges and limitations of using webcam data for geomorphological analysis.

 

(3)Results: The results section is well-presented and provides a clear description of the findings. The figures are well-designed and effectively illustrate the key points. However, it could be slightly improved by providing more details on the statistical analysis and error propagation methods used for the quantification of surface changes. Additionally, it would be helpful to include a more detailed discussion on the temporal specification of the individual geomorphic events identified in the study.

 

(4) Conclusion: The conclusion section is clear and provides a good summary of the main findings. However, it could be slightly improved by including a more detailed statement on the contributions of the study to the field of geomorphology and its implications for future research and volcanic monitoring.

 

In summary, the manuscript presents a valuable contribution to the field of geomorphology and provides new insights into the geomorphological processes in volcanic environments. With some minor improvements, the paper will be suitable for publication. I recommend accepting the manuscript for publication after the authors address the comments and suggestions provided in this review.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf