Applying an Analytic Hierarchy Process and a Geographic Information System for Assessment of Land Subsidence Risk Due to Drought: A Case Study in Ca Mau Peninsula, Vietnam

Round 1

Reviewer 1 Report

This paper doesn't interest me. But I think it has potential to be published. I suggest that the authors revise it.

1. I suggest authors emphasize their innovative contributions. There are thousands of papers that use GIS and AHP, so it's not innovative. Authors should identify innovations in the last part of the introduction. In addition, the last paragraph of introduction should be deleted. The structure of this article is not long, so it does not need a separate introduction.

2. I suggest that the authors explain why they chose these indicators and the reference basis for their grading criteria. This is very important.

3. The word "discussion" in title 3 is repeated. Title 4 is discussion.

4. The discussion section of this article is insufficient. I suggest complementing the contribution of research to sustainable development. Also, if possible, I suggest adding a comparison between the risk map and the reality.

5. Figure 6 is the most important, but it does not conform to scientific norms. Such as missing boundaries. Several classes of colors do not appear in the legend. The small figure at the top left has nothing to do with the result. Other figures have these problems as well.

Author Response

The authors would like to sincerely thank Reviewer 1 for the time spent reviewing the manuscript “Applying analytic hierarchy process and geographic information system for assessment of land subsidence risk due to drought: A case study in Ca Mau Peninsula, Vietnam”, (MS No. sustainability-2885810), and suggesting the positive comments. All suggestions have been incorporated in the revised manuscript and highlighted in red color. The manuscript is formatted as per the Sustainability Journal. The point-by-point response to all the comments is given in the author response form.

Author Response File: Author Response.pdf

Reviewer 2 Report

General Comments:

This paper studies the risk of land subsidence due to drought in the Ca Mau Peninsula region of Vietnam. The AHP method is used to determine the weights of influencing factors, and GIS techniques are used to overlay map layers of factors to delineate land subsidence risk zones. The research is innovative, the methodology is sound, and the paper is clearly structured and well-written. However, there are some aspects that could be improved.

Specific Comments:

1. The abstract is too brief, please expand to 200-300 words to more fully summarize the research content, methods, innovations, and main conclusions.

2. The literature review in section 2 paragraph 2 is too concise. Please supplement studies applying AHP and GIS for land subsidence risk assessment.

3. The explanation of the consistency test for the AHP method in section 2.2.1 is insufficient. Please add the specific formulas for calculating the consistency index and consistency ratio.

4. The specific scoring standards for normalizing the evaluation factors in section 2.2.2 are unclear. Please provide quantified scoring criteria.

5. The discussion section is too brief. Please expand to discuss regional differences in land subsidence, countermeasure suggestions, etc.

6. Please add a summary of innovations and limitations to the conclusion section.

7. The reference formats need to be unified, including paper titles, authors, sources, etc.

8. The resolution of some figures and tables is low, please replace with high resolution versions.

9. The language expression is fluent overall, but some sentences need to be revised for accuracy. Please have a native speaker proofread.

10. There are some formatting errors in the paper, please check carefully and revise.

I suggest a major revision.

Author Response

The authors would like to sincerely thank Reviewer 2 for the time spent reviewing the manuscript “Applying analytic hierarchy process and geographic information system for assessment of land subsidence risk due to drought: A case study in Ca Mau Peninsula, Vietnam”, (MS No. sustainability-2885810), and suggesting the positive comments. All suggestions have been incorporated in the revised manuscript and highlighted in red color. The manuscript is formatted as per the Sustainability Journal. The point-by-point response to all the comments is given in the author response form.

Author Response File: Author Response.pdf

Reviewer 3 Report

The review of “Establishing of risk zoning of land-subsidence map due to drought using GIS-AHP tools: A case study in Ca Mau Penin-Sula, Vietnam”

The article concerns the evaluation of risk subsidence on regional level (general level of spatial analysis). The methods applied involve:

 - AHP method to evaluate the weight of main factors that may determine the phenomena in the area of the study and

 - GIS tool to overlap maps presenting selected features of the area and present final map of subsidence risk zones.

The structure of the manuscript is correct. The specific( mostly positive) comments are as follows:

1. The introduction contains the relevant theoretical background and the review of the literature is relevant to the topic of the work,

2. The methodology concerning the AHP analytical hierarchy method, selected criteria in assessing the risk of land subsidence, data source, as well as the method of overlay influencing factors for building subsidence maps are clearly presented.

3. The results

- Standardisation criteria - the indicators established in the work and the sensitivity levels assigned to them are not very questionable. Some specific land feature are not clear (in case of land use: agricultural land and rural land) or rather site-specific (national defence and security land).

- Weight of valuation criteria - clearly presented; the final subsidence risk map for the area of the study provides useful information regarding the spatial extent of the certain risk level and can be applied in studies concerning regional land use strategies and policies.

4. Conclusions - the authors properly referred to the objectives formulated in the introduction and pointed out the limitation of the methods and the obtained results.

Figure 4 geological (b) soil (c) and land-use (e) - map legends are of poor quality.

In summary, the manuscript can be recommended for publishing in Sustainability Journal.

26.02.2024

Comments for author File: Comments.pdf

Author Response

The authors would like to sincerely thank Reviewer 3 for the time spent reviewing the manuscript “Applying analytic hierarchy process and geographic information system for assessment of land subsidence risk due to drought: A case study in Ca Mau Peninsula, Vietnam”, (MS No. sustainability-2885810), and suggesting the positive comments. All suggestions have been incorporated in the revised manuscript and highlighted in red color. The manuscript is formatted as per the Sustainability Journal. The point-by-point response to all the comments is given in the author response form.

Author Response File: Author Response.pdf

Reviewer 4 Report

GENERAL COMMENTS:

The study presents a methodology of using GIS and AHP tools for estabilighing subsidence risk maps in Ca Mau Peninsula in Vietnam.

The manuscript is well-structured but requires proof-editing service. Some parts of the text should be rewritten and reordered to improve legibility and facilitate its comprehension.

Many abbreviations appear throughout the manuscript without their explanation with some being obvious (but only for people from the GIS domain), whereas others were confusing. When abbreviations appear in the text for the first time, please expand and include abbreviation in the brackets but only if they appear more than once throughout the manuscript.

I have two major concerns regarding this study. First, in my opinion it lacks novelty. Authors provide numerous references to other studies applying similar methods to theirs but applied to different case-study areas. No research questions are asked in this manuscript but rather research aims are stated, making this look more like a report than a research paper.

The weakest side of this manuscript however is its subjectivity. I am really missing reasoning behind the factors that were selected. how were their values normalized and what weights were assigned to them in the AHP process? One of the factors, namely evaporation in the dry season, bases on an experimental formula. What is this formula? How was it calculated? All that leaves an impression of a work that was designed in such a way to match the expected results of land-subsidence risk zones in the study area.

With that being said I am sorry to reject the paper in its current form. This work has potential to be published but authors should focus more on methodology than the literature review (which is profound). If an experimental formula has been applied, why not highlighting it? This could be your scientific input! Perhaps, authors could play around with the weights of particular factors to see how will this impact the final results and draw some conclusions out of it? This part could be scripted so that others could use it in the future for their purposes: different case studies or weighting of factors.

Nevertheless, I wish the authors all the best in their research work and hope to see the paper published in the future, after improving its methodological part.

Below are some detailed comments that refer to particular parts of this manuscript.

DETAILED COMMENTS:

>> Title: it could be shortened

>> Lines 20-21: do not introduce abbreviations in the abstract

>> Line 34: What does a 'model method' mean? Besides, as far as I'm concerned, the reference 8 applies ANN.

>> Lines 39-40: If so, then why are you using an approach that generates lower predition accuracy?

>> Lines 75-76: This forecast doesn't tell me much as a person from outside of this region. Is inland navigation developed in this place and will such a low depth make it impossible?

>> Line 77: I am not familiar with the term 1-D consolidation. Please provide brief in-text explanation.

>> Lines 96-99: Since this is supposed to be a research paper, you should rather talk about research questions than the study objectives. Please highlight novelty of your approach and aim to answer more scientific questions. "Applying GIS technology to overlap map layers to determine subsidence risk zones" sounds more like one element of the workflop applied in your methodology.

>> Figure 3: In caption - please add 'based on...'

>> Lines 144-150: If I weren't familiar with the AHP method, I wouldn't understand it from such a description. Please rewrite this section.

>> Lines 161-162: It would be nice to highlight that it's the original assumption by Saaty.

>> Table 2: please provide references to the data sources. Can everyone access them?

>> Table 2 - evaporation in the dry season: what is this experimental formula? Why isn't it explained?

>> Eq 3: wouldn't it be more intuitive to use letters corresponding with the factors rather than numbers? E.g. Wgeo*YTgeo rather than W1*YT1

>> Lines 203-210: This, along with the links to the online sources (if available) should be included in Table 2.

>> Line 217: Should be table 2
>> Tables 4-9: Please use the same order as these factors appear in Figure 4 - this would facilitate reading. But more importantly, what is the reasoning behind such sensitivity assignment? This looks very subjective.

>> Table 4: amQ3IV1 appears twice. Please cross-check with the caption.

>> Table 6: It would be nice to apply the same colour scale in Figure 4 e)

>> Lines 225-227: This should appear right under Table 4

>> Figure 5: Yet another ordering type. Please be consistent throughout the manuscript.

>> Table 10: Is there any reasoning behind such an approach? Authors must elaborate on this part as it's the core of their methodology. Why is the land use factor way more important than the geological one?

>> Table 11: And what are the CI and CR values here? Is the CR lower or equal to 0.1?

>> Table 12: It's a matter of rounding, but Ratio[%] column does not sum to 100%

>> Line 277: 'and many more in general' - such an expression should not appear in a scientific paper.

>> Lines 294-299: This looks like authors applied weights to particular factors in a way that would produce the expected results.

>> Lines 306-307: I must disagree. First, you normalize values of particular factors without proper reasoning and then you assign weights in a similar wait. This is a subjective part.

The manuscript requires proof-reading service. It's comprehensible but at times I had troubles with going through it smoothly.

Author Response

The authors would like to sincerely thank Reviewer 4 for the time spent reviewing the manuscript “Applying analytic hierarchy process and geographic information system for assessment of land subsidence risk due to drought: A case study in Ca Mau Peninsula, Vietnam”, (MS No. sustainability-2885810), and suggesting the positive comments. All suggestions have been incorporated in the revised manuscript and highlighted in red color. The manuscript is formatted as per the Sustainability Journal. The point-by-point response to all the comments is given in the author response form.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

After revision, the level of the article has improved. I suggest that this article be published. But before that, I suggest the authors add some literature citations in terms of index selection and scoring criteria.

Author Response

The authors would like to sincerely thanks the Editor-in-chief, Associated Editor and Reviewers #1 for the time spent reviewing the revised manuscript R1 “Applying analytic hierarchy process and geographic information system for assessment of land subsidence risk due to drought: A case study in Ca Mau Peninsula, Vietnam”, (MS No. sustainability-2885810), and suggesting the positive comments. All suggestions have been incorporated in the revised manuscript R2 and highlighted in purple and yellow color. The manuscript is formatted as per the Sustainability Journal. The point-by-point response to the comments is given in the author response form.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors have responded all my concerns. I think it is acceptable for publication.

Author Response

The authors would like to sincerely thanks the Editor-in-chief, Associated Editor and Reviewers #2 for the time spent reviewing the revised manuscript R1 “Applying analytic hierarchy process and geographic information system for assessment of land subsidence risk due to drought: A case study in Ca Mau Peninsula, Vietnam”, (MS No. sustainability-2885810), and suggesting the positive comments. All suggestions have been incorporated in the revised manuscript R2 and highlighted in purple and yellow color. The manuscript is formatted as per the Sustainability Journal. The point-by-point response to the comments is given in the author response form.

Author Response File: Author Response.pdf

Reviewer 4 Report

Dear authors, thank you for revising the manuscript according to my and other reviewers’ comments. After carefully analyzing the reviews, I am still not completely satisfied with the manuscript. In this review I will first refer to your responses to my general comments from the first round of reviews and then move to more detailed comments.

My biggest concern about this manuscript is again its lack of novelty although some interesting methods have been described. Having this in mind, I am really surprised that the whole part of methodology that based on Delphi and KAMET rule table was omitted in the first version of the manuscript. Why? It’s of great importance! Nevertheless, either I am missing something or the results (Table 6) don’t really follow the assumptions (Table 2) in this aspect. Besides, the whole process in your case study is not clearly described, e.g. who were the experts evaluating the factors? How was the initial set of preliminary indicators selected (line 356, table 6)?

Table 5 describes the selected criteria but these derive from table 6 (preliminary factors) that appears later in the text. That introduces some unnecessary chaos!

Unfortunately, I don’t feel satisfied with the revisions. Although some technical details have been added (especially in the methodology section), I still find this manuscript a kind of a report rather than a scientific article. The methodology is described more clearly now and I appreciate it but why wasn’t it present in the first version of the manuscript?

My recommendation is to publish the paper but in my opinion it still requires major revisions. Perhaps other reviewers will be satisfied with your revisions as they appear now, which will lead to a positive assessment of the manuscript by the journal’s editor.

AUTHORS: The authors added more previous studies using AHP method and GIS to evaluate such as land suitability for paddy rice crops, flash flood risks, landslide risk, evaluating the risk of subsedence and soil erosion, etc.

>> As I wrote in one of the following comments, the literature review is quite impressive here. What required improvements the most was the methodology section. I am aware of the fact that other reviewers required more profound literature review.

AUTHORS: Most studies evaluate subsidence due to the impacts of structures and bank landslides that cause the subsidence of surrounding land, but there are very few studies on subsidence due to the impact of prolonged drought. This is one of the novelties of this study. The study uses the Delphi method and the KAMET rule table to analyze and select indicators that affect subsidence. The results can be used to assess the risk of subsidence due to prolonged drought in areas with similar characteristics to the Ca Mau peninsula. This is an area severely affected by drought, prolonged saltwater intrusion, and river water decline, which lead to increased groundwater exploitation. There is no exogenous flow. The study results answered the following question: how does drought affect land subsidence?

>> Authors indicate that studies analyzing the impact of prolonged droughts do exist. If so, why aren't they directly cited here? I assume they answer the same research questions as the authors posed in this manuscript. If so, what is the novelty here, apart from a different case study area?

AUTHORS: The authors agree with the reviewer about the subjectivity when determining the influence weight of factors when using the expert method. However, the study results have shown areas at risk of subsidence that are quite consistent with the actual situation that has been occurring in the study area.

>> That is good but how about if the proposed methodology was applied to a different case study area? The applied methodology might have worked here as authors were familiar with the study area and its characteristics but could it be universally applied...?

AUTHORS: The study results have some limitations. The main limitation is the use of the method of overlapping map layers, in which map layers with determined weights were stacked on top of each other to identify locations at risk of subsidence in the study area. The processing of some map layers may have had errors, such as the dry-season evaporation map and the dry-season water flow map, which were built based on factors using calculation formulas, so they could not avoid work errors. In addition, the hydrometeorological station locations in the study area were quite sparse, leading to the interpolated values not being perfectly accurate.

>> I don't understand this reasoning. Fine, interpolation of data from a sparse network of points may generate errors but the "use of calculation formulas" itself? Why would they produce "work errors" and what does it actually mean? 

AUTHORS: Furthermore, the weighting of the influencing factors used expert methods, so subjective assessments could not be avoided. However, the weights of these influencing factors can change over time to gradually match reality.

>> How can this be achieved? Again, when proposing a methodology in a research paper, one should aim to develop the one that is as universal as possible. Tweaking weights of particular factors is fine but how to do that? Are there any assumptions and/or recommendations on how might they change over time? If that's the case, they should be described.

AUTHORS: Sincerely thank you for your very important comments and pointing out gaps in the author's research. Based on the very frank and constructive comments, the author also tried awfully hard and seriously edited and completed the manuscript in the best way and ensured logic and scientific content. Certainly not stopping at the results of this research, the authors will continue to update more data and validation the weight of factors to build a warning system to assess the risk of subsidence during the dry season for the study area.

>> First of all, all the planned future studies should be described somewhere at the end of the manuscript. But more importantly, the so-called “experimental formulae” turned out to be existing formule by Penman-Monteith and Conservation Service’s Curve Number Method (although they still appear as “experimental formulae” in Table 5). As I pointed out in my first review, these formulae could be the novelty I was looking for in the manuscript.

DETAILED COMMENTS:

 Comment: First you should write the full name and then put abbreviation in brackets, i.e. Remote Sensing (RS) rather than RS (Remote Sensing). By the way, you introduce RS but in line 117 one can find ‘remote sensing’. There is no point to introduce an abbreviation if it only appears once throughout the manuscript.

Original remark: Lines 39-40: If so, then why are you using an approach that generates lower prediction accuracy?

AUTHORS: Because of the current characteristics and data of the research area, the selected method can provide results with more reliable accuracy.

Comment: This explanation should appear in the text.

Original remark: Lines 144-150: If I weren't familiar with the AHP method, I wouldn't understand it from such a description. Please rewrite this section.

AUTHORS: The analytic hierarchy process (AHP) is a pairwise comparison method of measurement theory [34]. It divides problems into factors, then arranges them into a hierarchy chart. After that, the value of each factor is compared in order to determine the most significant factor and choice. Rattanavarin [35] concluded that the AHP has the following advantages: it is (a) easy to use, as data are in form of a hierarchy chart; (b) precise; (c) easy to prioritize, as results are in form of digits; and (d) capable of handling both subjective and objective factors, and it (e) eliminates any bias in a decision. The AHP has been used in various areas of decision making. Cheng et al. [48] constructed an AHP method with eight steps as follows: (a) Cleary define the decision problem. (b) Define the criteria related to the decision problem. This is achieved through a number of literature reviews in the studied areas. (c) Set up a decision hierarchy in which the first level represents the goal of decision making. The second level displays the main criteria. The third level includes secondary criteria (these are optional and are included if the main criteria are not clear), and the last level includes choices. (d) Collect data from experts. (e) Construct a matrix to employ pairwise comparison.

Comment: Watch for typos in this fragment, e.g. ‘cleary’. Nevertheless, although I was the one complaining about too brief description of AHP, the proposed one is in my opinion too lengthy. Naming all the 8 steps from some other study is too much.

Comment: Lines 206-207 – I believe authors talk about relation and not relevance. Please correct.

Comment: Table 1 is formatted in a weird way.

Comment: Table 6 - If I’m not wrong, then that if in round 1 a particular index was given lower average relevance score than 3.5 then it gets eliminated. If so, I would like to see full results in Table 6 (no information on Mqi). Besides, based on the KAMET rules, Land use characteristics index got accepted in Round 2 (cross-check the round numbering with table 2). If so, then why is there further information under Round 3 and the data are repeated? Besides, table 2 introduces abbreviations (e.g. Mqi), whereas in table 6 full names are used. Please double-check the results in table 6 because either there are some errors or I am missing something.

Original comment: Figure 5: Yet another ordering type. Please be consistent throughout the manuscript.

AUTHORS: Could the reviewer explain the requirement to modify in Figure 5?

Comment: The order of maps in Figure 5 (Geology, Soil. Groundwater exploitation…) did not match the order of factors in other parts of the text. They should be consistent to facilitate reading.

Original comment: Lines 306-307: I must disagree. First, you normalize values of particular factors without proper reasoning and then you assign weights in a similar wait. This is a subjective part.

AUTHORS: The author has added 8 steps to select factors affecting subsidence in the study area, necessary information to be able to provide an assessment scale for influencing factors as well as weights of factors. That leads to subsidence in the study area. The author has added an overview of the Delphi method and KAMET rules in identifying 6 main influencing factors; basis for evaluating the weight of each index in each factor class.

Comment: This is an important thing! This is the methodology description I was missing. Thank you for this update and I don’t really understand why it didn’t appear in the original version of the manuscript. Nevertheless, I am still missing some points… Who were the experts who took part in assessment? How many of them were involved? How long did it take to run all the 3 rounds of KAMET rules assessment?

It looks like only the original parts of the manuscript underwent proofreading service. Many typos appear in the newly added parts of the text, some greatly affecting the manuscript's reception (e.g. irrelevant vs unrelated). I highlighted some of them but authors must perform some thorough analysis of the text.

Author Response

The authors would like to sincerely thanks the Editor-in-chief, Associated Editor and Reviewers #4 for the time spent reviewing the revised manuscript R1 “Applying analytic hierarchy process and geographic information system for assessment of land subsidence risk due to drought: A case study in Ca Mau Peninsula, Vietnam”, (MS No. sustainability-2885810), and suggesting the positive comments. All suggestions have been incorporated in the revised manuscript R2 and highlighted in purple and yellow color. The manuscript is formatted as per the Sustainability Journal. The point-by-point response to the comments is given in the author response form.

Author Response File: Author Response.pdf

Round 3

Reviewer 4 Report

Dear authors, 

thank you for your responses and improvements. I am (almost) happy with the article's current shape. Some comments below:

>> I believe that at this stage it is more a comment to the editorial board but the newly written parts require proofreading, see for example lines 229-230.

>> Table 1 - I still don't understand why it has these empty rows.

>> Lines 333-340 - are there 12 experts in total or rather 12+1+1+10 = 24? Besides, caption of Table 5 should explain, why some rows are marked in red.

>> Formulae in Table 7 should have references provided just like in the text.

>> After all these modiffications, please once again carefully examine the references section.

Good luck in your future research activities!

The newly added parts of the text require proofreading. See for example lines 229-230.

Author Response

The authors would like to sincerely thanks the Editor-in-chief, Associated Editor and Reviewers # 4 for the time spent reviewing the revised manuscript R2 “Applying analytic hierarchy process and geographic information system for assessment of land subsidence risk due to drought: A case study in Ca Mau Peninsula, Vietnam”, (MS No. sustainability-2885810), and suggesting the positive comments. All suggestions have been incorporated in the revised manuscript R3 and highlighted in purple and yellow color. The manuscript is formatted as per the Sustainability Journal. The point-by-point response to all the comments is given in the author response form.

Author Response File: Author Response.pdf