Review Reports - Influence of Cumulative Geotechnical Deterioration on Mass Movement at a Medium-Scale Regional Analysis (Cortinas Sector, Toledo, Colombia)

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript analyzes the evolution of geo-environmental conditions and geotechnical susceptibility between 2016 and 2021 in the Cortinas.

The manuscript proposes a new concept of cumulative geotechnical degradation (AGD), has been proposed, which is interesting and significant. Some minor comments for your reference:

(1) Add relevant content on data sources and processing methods.

(2) For the AGD, provide more case studies or analysis to enhance the strength of the association with landslide occurrence.

(3) The research focuses on the period from 2016 to 2021, adding the latest research in recent years.

Author Response

Dear Reviewer: We appreciate that you consider our contribution to be “interesting and significant”. We welcome your comments because they generate added value for our project, which is why we proceed to give the respective responses, which will be implemented in the article document.

(1) Add relevant content on data sources and processing methods.

Answer: Our main source of data is the information collected through engineering work over 33 years of observation and trial and error decisions that have served to feed a more in-depth investigation since 2016, when more than 50 instability events occurred in the study area in the previous year, affecting oil and gas transmission lines, electrical towers, roads and properties. This information is presented in section 1 (Introduction). Another important source is precisely the method included in the mass removal threat zoning manuals of the Colombian Geological Service (SGC), the leading state entity on this subject. This research does not present a new method, but rather relies on the previous one to be complemented with the concept of Accumulated Geotechnical Deterioration (DGA) as the main contribution. Additionally, we had all the historical information on instability events that occurred along the Oil & Gas transportation lines, a consulting service that we have carried out, nourished by reports, diagnoses, designs and aerial images from different years, as well as the historical memory of professionals and communities that have experienced these phenomena firsthand. The information from historical records of SIMMA, IDEAM and SGC in relation to old landslides, rains and earthquakes.

It should be noted that this article is the beginning of the research, which is intended to analyze and present from a smaller to a larger scale through screening, a procedure that allows the most predominant factors to be selected as appropriate. For large areas of land, it is not feasible to carry out detailed exploration and analysis, therefore, the sequence of the different scales allows us to concentrate on the most dangerous areas. Through traditional methodologies and even some recent ones from Colombia (SGC-2016) they are based on determining the areas of greatest danger, which is completely valid, however, a proper approach is not made towards prevention that allows establishing a priori the occurrence of potential instability phenomena. The continuity of the research is based on the following scales, which will be reflected in the corresponding articles that are based on the 1:5000 and 1:2,000 scales of the respective screening mentioned, for which we hope to have your valuable comments. In the following articles, certain modifications are made to the methods of larger scales and multiple field data from different dates associated with the same place are included, but under the requirements of the method of each scale it is necessary to consider them, since the first sieve of the 1:25,000 scale focuses more on geology, geomorphology and vegetation cover.

According to your observation, we consider it pertinent to highlight these sources and methods within the article, which was recorded in it.

(2) For the AGD, provide more case studies or analysis to enhance the strength of the association with landslide occurrence.

Answer: As mentioned in the response to the previous comment, the area where the Oil & Gas transmission lines run during their operation has been affected by different landslides that have even caused the suspension of the service. It has not been possible to establish a prediction of the occurrence of these phenomena in places where, even though the triggers of earthquake and rain have been similar or even greater than in the cases where it has occurred, which supports the need to include the DGA to understand why in such similar cases a new failure has not occurred. Throughout history we have concentrated on studying the phenomena when they occur based solely on the behavior of the triggers and not on the change of the conditioning factors (DGA) under the interaction of the previous factors. Our hypothesis is based on the fact that for an instability event to occur it does not necessarily obey a threshold of rain and earthquake but rather the form of deterioration that the terrain suffers so that the precise geotechnical conditions for the occurrence occur. It should be noted that, when we talk about deterioration (DGA), recovery processes occur over time, which makes the prediction model even more complex to determine. The DGA is not represented by a decreasing curve of the ground's resistance, but rather a variable curve of ascents and descents (set theory) to reach its convergence.

For the above reasons, we believe it is pertinent to include other similar cases in a general way that help to support our hypothesis. These cases are included in the section on the application of the DGA method.

(3) The research focuses on the period from 2016 to 2021, adding the latest research in recent years.

Answer: Indeed, we believe it is pertinent to include information on certain activities carried out between 2022 and today, since there is topographic monitoring, rainfall records and recent aerial images. This information is presented in the section on the application of the DGA method.

We hope that the above responses will clarify your comments and improve the content of the article. We remain attentive to any concerns.

Sincerely,

Carlos Buenahora. University of Salamanca

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Editor and Authors,

I have revised the manuscript entitled: Influence of Cumulative Geotechnical Deterioration on Mass Movement at a Regional Analysis Scale 1:25000 (Cortinas Sector, Toledo, Colombia). The aim of this study is to assess the susceptibility and landslide hazard in the area known as Cortinas, in Colombia. The methodology for threat assessment at a scale of 1:25,000 developed by the Colombian Geological Service was implemented. Two different periods (2016 and 2021), employing GIS tools, were considered for analysis. The topic of the manuscript is certainly suitable for the journal and of potential international interest, but the manuscript can not be accepted for publication in its present form and a major revision is request. The methods and techniques applied are very common. The manuscript shows no new ideas, no advanced techniques or no attractive findings. Nevertheless, the manuscript presents a good case study. The main problem of the paper is that it appears confused and low fluid and in many part the methodology applied should be better described. No interesting details about the data specification and study area that show the uniqueness of the problem statement with the hypothesis and findings no in depth discussion, only presenting the results in general manner and often unclear. Also, the Authors should better highlight the novelty of the applied methodology and their points of force. Many data are presented, which is either not clear how was obtained and/or discussed in depth. The discussion failed to present a clear story but rather includes several issues, which were discussed in a superficial way.

I found the text difficult to read. Some of the sections are used unconventionally. Some suggestions are listed below:

1) Abstract section is so general and does not have a scientific structure as a research paper.

2) Introduction section is not well written. Please add the novelty of research. How it is different from past studies. Also the authors should focus better the aims of the work. Most sentences in the Introduction section are general and do not have a scientific structure. Also, the research background about the proposed subject and methods has not been appropriately mentioned, especially about the methodologies applied. I would recommend add some recent research articles to reconstruct this section with extensive literature. For example:

-Wang, L.J.; Guo, M.; Sawada, K.; Lin, J.; Zhang, J. A comparative study of landslide susceptibility maps using logistic regression, frequency ratio, decision tree, weights of evidence and artificial neural network. Geosci. J. 2016, 20, 117–136.

- Reichenbach P, Rossi M, Malamud BD, Mihir M, Guzzetti F (2018) A review of statistically-based landslide susceptibility models. Earth Sci Rev 180:60–91;

- Conforti M., Borrelli. L., Cofone G., Gullà G. 2023. Exploring performance and robustness of shallow landslide susceptibility modeling at regional scale using different training and testing sets. Environmental Earth Sciences 82:161.

3) The aims of the paper should be better define. Please add the novelty of research. How it is different from past studies.

4) The methodology section was vaguely written, so it is hard to understand the constitution of the model/study. So, my suggestion is to reconstruct it. Author need to review more about adopted methods.

5) I suggest to add a flowchart to better explain the methodology applied and all the data used.

6) The Authors, should explain why choice only these 4 landslide conditioning factors. In literature, many papers, for assess the landslide susceptibility which using a lot of others geo-environmental factors.

7) No critical analysis of results has been reported in the paper. In many parts of the result section, there often is confusion between the methodology applied and results obtained.

8) I did not see any note about the comparison between the obtained results of the current research and previous research.

9) The discussion section must be better benchmarked with the published literature. Moreover, many parts of the text are results not discussion. The main goal of the current research should clearly and concisely explain the main scientific contributions of this work.

10) The conclusion are very short and does not have any scientific structure and should be rewritten. In conclusion section, you have to mention the implications of your research and how it makes a footprint in scientific research. Try to incorporate your work to global interest how this research has worldwide importance. It will be interesting for the readers. The authors must emphasize that their work can be successfully used in other regions and settings, because this justify the publication in an international journal.

Applying all the corrections to your manuscript, it will be significantly improved and should be able to get published in the next step.

Author Response

Dear Reviewer: We appreciate that you have considered accepting this article. We welcome your comments because they add value to our project, which is why we are proceeding to give the respective responses.

1) Abstract section is so general and does not have a scientific structure as a research paper.

Answer: We agree and it was adjusted, focusing on novelty and results.

- Reichenbach P, Rossi M, Malamud BD, Mihir M, Guzzetti F (2018) A review of statistically-based landslide susceptibility models. Earth Sci Rev 180:60–91;

Answer: We made adjustments to the introduction, including a short preamble, a description of the problem, historical background, purpose and the novelty of the contribution. The articles referenced by you were taken into account.

3) The aims of the paper should be better define. Please add the novelty of research. How it is different from past studies.

Answer: The result, its innovation and comparison with other traditional methods are highlighted. The present article aims to analyze the geoenvironmental conditions between 2016 and 2021 in the sector known as Cortinas (Toledo, Colombia), applying, for this purpose, the innovative concept of "Accumulated Geotechnical Deterioration" in order to explain the evolution of susceptibility over time from the perspective of prediction, which under traditional methodologies is not duly considered, since unlike what has been thought, the conditioning factors do change in the short and medium term, especially in tropical areas. The above is highlighted in the conclusions and is expanded a little further in section 5.6.

Answer: The methodology indicated by the SGC for the 1:25,000 scale (which is not described in detail to provide space for own concepts) includes the conditioning factors which constitute the object of this article (see figure 5); for this reason, both its structure and its sequence have been respected, since its discussion does not constitute the focus of the research. However, the way in which the constitution of the model/study is understood was reviewed and modified.

5) I suggest to add a flowchart to better explain the methodology applied and all the data used.

Answer: Ok, it is included. It should be noted that the SGC methodology and its flow chart are adopted, to which the DGA concept is added as a complement to achieve a better approximation towards the prediction of the FRM.

Answer: As indicated, this article, without any modifications, is framed within the SGC methodology for the 125,000 scale, which considers these conditioning factors, as it is considered a great recent contribution in Colombia for the evaluation of FRM that have occurred and those that may occur. In the following articles, 1:5,000 and 1:2000, for which there is their own methodology, the multiple conditioning factors that are related to susceptibility will be included. This concept is clarified in the article. At a medium scale (1:25,000), the conditioning factors themselves do not vary much given that the perspective is more focused on general geology and practically the only variable factors in the short and medium term are the vegetation cover and the geomorphology obtained from the interpretation of high-resolution aerial images.

7) No critical analysis of results has been reported in the paper. In many parts of the result section, there often is confusion between the methodology applied and results obtained.

Answer: A critical analysis of the results is included in the discussion to provide greater clarity to the difference between the adopted methodology and the new concept of DGA.

8) I did not see any note about the comparison between the obtained results of the current research and previous research.

Answer: A critical analysis of the results is included in the discussion to provide greater clarity to the difference between the adopted methodology and the new concept of DGA.

Answer: A comparison is made with the existing literature and the discussion regarding the results is strengthened with the scientific contribution of this work.

Answer: The conclusions are rewritten and supplemented, focusing on the contributions of research at a global level: where frequent landslides are recorded, where the climate is tropical and where abundant recent slope deposits are present.

We hope that the above responses will clarify your comments and improve the content of the article. We remain attentive to any concerns.

Sincerely,

Carlos Buenahora. University of Salamanca

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

The article deals with a very interesting topic regarding the ‘Influence of Cumulative Geotechnical Deterioration on Mass Movement at a Regional Analysis Scale 1:25000’. Overall, it is a comprehensive article and the findings provided indicate that a great deal of effort was put in. Suggestions for improvements that could be performed to the manuscript prior to its publication are the following:

- Title: It is suggested to avoid numerical references in the title (alternative phrases such as medium/large/small etc scale could be used).

- Abstract: It is suggested to avoid acronyms and numbers in this part of the manuscript in order to keep the Abstract simple yet informative. Those could be addressed in more detail throughout the following parts of the article. Try to mention the general results of the research, as well as the innovations of the research proposed compared to previous similar studies.

-Line 49: It would be interesting to add more relevant references regarding the methodologies that are mentioned.

-Lines 68-69: It is suggested to add more information (and maybe references) related to the methodology for threat assessment at a scale of 1:25,000. In addition, why 2016 and 2021 were selected as study periods? (more data available?) Why did the authors select to use only two dates and not more and how could this affect the final results? What are the innovations of your research compared to previous similar studies?

-Lines 128 &163: Regarding the various methodologies provided by the Colombian Geological Survey, it is suggested to analyze this section a bit further adding some more relevant details (describe the methodologies more clearly)

- Figure 3: How did these results occur? What parameters were taken into account and what SW was used in order to generate the presented results?

- Figure 4: What is the source of this image? For example, is it a rectified image taken from a plane/ an unmanned aerial vehicle or a satellite image and what is its resolution?

-Regarding the whole section ‘4. Methods of analysis': methodological and susceptibility analysis, as well as the triggering factors are well presented. However, the specific connection with this study is not very clear. In what ways all these factors were taken into account in order to conclude your research? What is the practical concept behind the theoretical one and how is this connected with the next section 5?

-The use of in situ data is not presented very clearly, although this type of data is very valuable with regard to landslide studies. What could be some possible divergences in the results if there is a lack of this type of data? (this could also be discussed in the last part – Conclusions).

- It is suggested to add a general workflow in order to facilitate reading and help readers follow up with your methodologies.

Conclusions:

- It is suggested to underline more the novelties that the proposed method offers.

- It would be interesting to add a comment about any other factors that could affect the proposed methods (for instance: image terrain, type of sensors, the time difference between the image samples that were used, etc.). It is also suggested to comment a bit more on future work and any other future challenges that need to be tackled. In general, the article is very analytical however, it is suggested to pay attention to the methodologies presented and provide more information.

Comments on the Quality of English Language

Minor editing of English is language required.

Author Response

Dear Reviewer: We appreciate that you consider our contribution to be “interesting and comprehensive” and we value your recognition of our efforts. We welcome your comments because they add value to our project, which is why we are proceeding to give the respective responses.

- Title: It is suggested to avoid numerical references in the title (alternative phrases such as medium/large/small etc scale could be used).

Answer: Ok, based on your recommendation and referring to the JTC-1, 2008 guide, the expression 1:25,000 is adjusted to a “medium” scale.

Answer: Agreed. The acronym DGA is removed and reference is made to a medium scale instead of writing 1:25,000. Additionally, the abstract is adjusted to highlight the result, its innovation and comparison with other traditional methods under the journal's specification of not exceeding the number of words.

-Line 49: It would be interesting to add more relevant references regarding the methodologies that are mentioned.

Answer: The methodologies of the SGC are mentioned (Fell et al. [2008]; Aleotti and Chowdhury [1999]; Carrara [1983]; Reichenbach [1999]; van Westen et al. [2006]) as well as those of Wang, L.J.; Guo, M.; Sawada, K.; Lin, J.; Zhang, J. A comparative study of landslide susceptibility maps using logistic regression, frequency ratio, decision tree, weights of evidence and artificial neural network. Geosci. J. 2016, 20). As well as, - Reichenbach P, Rossi M, Malamud BD, Mihir M, Guzzetti F (2018) A review of statistically-based landslide susceptibility models. Earth Sci Rev 180.

Answer: Consequently, it is worth mentioning that the purpose of the article is not focused on the threat assessment methodology, since an existing one is being applied and sections 4 and 5 are dedicated to this. The true contribution of the research is the DGA within the results of the application of an existing methodology. The years 2016 and 2021 were used because they are precisely the two years in which studies were carried out (baseline and year of recent landslides), however, in the Vegetation Cover conditioning factor, an image interpretation analysis is used from 2012. We think the comment is correct and therefore we will include general information on the current conditions and the activities that have been carried out since 2021, such as aerial image taking, topographic monitoring and rainfall analysis. As mentioned, it is important to have more information, this article is limited to these years and a recommendation is made on the usefulness of continuing monitoring.

According to the adjusted summary, the present article aims to analyze the geoenvironmental conditions between 2016 and 2021 in the sector known as Cortinas (Toledo, Colombia), applying, for this purpose, the innovative concept of "Accumulated Geotechnical Deterioration" in order to explain the evolution of susceptibility over time from the perspective of prediction, which under traditional methodologies is not duly considered, since unlike what has been thought, the conditioning factors do change in the short and medium term, especially in tropical areas. The above is highlighted in the conclusions and is expanded a little further in section 5.6.

Answer: In order to provide space within the article for the concept of DGA, we adopt and explain the methodology of the SGC in sections 4 and 5, which is already known and has been formulated based on others. We will expand on the explanation of the DGA in section 5.6.

- Figure 3: How did these results occur? What parameters were taken into account and what SW was used in order to generate the presented results?

Answer: The results are obtained from the application of the QMS methodology during the year 2017 (baseline), at a scale of 1:100,000 and 1:5,000 using a GIS in the ARGIS software, where it is observed that, in this case, at Applying greater detail reduces the extent of the high threat area and increases the low one; However, it was precisely in these areas that the 2021 landslides occurred and spread to the lower part of the slope. The above shows that the traditional hazard assessment model has certain inaccuracies and this is where it is necessary to involve the DGA concept and take into account that carrying out a more detailed analysis does not mean that it is more effective, although it does. necessary under certain adjustments that will be part of the content of the second and third article of this research. Consequently, if the danger category changes to larger scales (5000), the interpretation of the smaller scales (100,000) should not be left aside, because the situation described above occurs. The 1:25,000 scale parameters correspond to photointerpretation and secondary information on geology, geomorphology and vegetation cover. On the other hand, the 1:5,000 scale (object of the following article) takes into account geotechnical parameters obtained through direct and indirect exploration and laboratory tests applying the infinite slope model, which we hope to have your valuable support in the review. of the sequence of the following articles of this research.

- Figure 4: What is the source of this image? For example, is it a rectified image taken from a plane/ an unmanned aerial vehicle or a satellite image and what is its resolution?

Answer: Image 4 corresponds to a superposition of an image taken with a drone with a 20 centimeter resolution, over a Google Earth satellite image, this is clarified within the article.

Answer: The connection between the application of the QMS methodology with the new DGA concept lies in the fact that the changes in vegetation cover allow us to compare the results of the analyzes carried out at a scale of 1:25,000 in the years 2017, 2021 and today (conceptual), which is precisely one of the inputs of the model. If the change in vegetation cover and geomorphology is not taken into account at this scale of analysis, the DGA concept could not be involved. The decrease in vegetation cover in the analyzed time period implies a decrease in the geotechnical parameters of the soils that make up the slope and that are associated with the DGA, which for the purposes of this research will be presented in the following articles. Once the susceptibility of the two reference years was determined, the triggering factors were applied in the analysis of the cause of the 2021 landslides, which for the 1:25,000 scale is done conceptually. Section 5, in its entirety, shows the results of the practical application of the model that is explained theoretically in section 4. These results are associated with the DGA since the changes in coverage from one model to another modified the areas of zoning in each category.

Answer: If changes in the conditioning factors are not taken into account, which for this scale are only represented through vegetation cover and changes in geomorphology, the DGA and the consequent changes in the hazard zoning could not be identified. This comment is included in the conclusions section given its relevance. It is clarified that for this working scale (1:25,000) there is no data taken “in situ” since, as explained, only the photointerpretation of high-resolution images and geological and geomorphological reference information is taken into account.

- It is suggested to add a general workflow in order to facilitate reading and help readers follow up with your methodologies.

Answer: This flow chart is included for the purpose of facilitating reading and interpretation.

- It is suggested to underline more the novelties that the proposed method offers.

Answer: We completely agree with the suggestion and it is included in the document.

Answer: An important factor that could affect the effectiveness of the applied model and its connection with the DGA is the periodicity of taking the aerial images for photointerpretation, given that it is possible that important changes cannot be perceived that lead to an imprecise interpretation. A process that would help determine more quickly and perhaps more accurately is to involve an AI model. The images should not be limited to planimetric information, but on the contrary should involve altimetry as much as possible in order to show possible changes in the geoforms that, even though they are minor, can contribute to the diagnosis.

It is also suggested to comment a bit more on future work and any other future challenges that need to be tackled. In general, the article is very analytical however, it is suggested to pay attention to the methodologies presented and provide more information.

Answer: A process that would help determine more quickly and perhaps more accurately is to involve an AI model. The short-term challenge is to document the methodologies on larger scales, where the type of analysis and type of exploration will be proposed to establish its relationship with the DGA and apply it in a model closer to predicting the occurrence of removal phenomena. mass. As well as, the importance of acquiring permanent data and establishing a general culture of the need to apply these concepts. This was clarified in the article.

We hope that the above responses will clarify your comments and improve the content of the article. We remain attentive to any concerns.

Sincerely,

Carlos Buenahora. University of Salamanca

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Editor and Authors,

I have revised the new version of manuscript and the my opinion is that the quality of the work, respect to first version, has been greatly improved considering all the suggestions of the reviewers. The Authors have discussed with great attention and wealth of details the items of the research. The paper appears well constructed and well documented. Hence, it is recommended that the manuscript now can be accepted for publication in its present form.

Reviewer 3 Report

Comments and Suggestions for Authors

Authors tried their best to incorporate all the comments, in order to improve the quality of the manuscript.

After the first revision and the changes addressed, the article is suitable for publication.

Comments on the Quality of English Language

The authors tried their best to incorporate all the comments, in order to improve the quality of the manuscript.

After the first revision and the changes addressed, the article is suitable for publication.