Assessment of Soil Loss from Land Cover Changes in the Nan River Basin, Thailand

Round 1

Reviewer 1 Report

The author tackles the soil loss in the Nan River Basin, Thailand based on land cover changes. This study is based on a widely used (R)USLE method, the author makes estimation on the factors in 2001 and 2019, and compares the two datasets.

The paper has several deficiencies.

The abstract is not satisfying. Formally, it exceeds the allowed length (200 words) by 10%. 

The sentence "Elevation and slope analyses highlight the vulnerability of elevated and steep terrain to soil erosion" provides no new information, therefore it should not be in the abstract.

Content

There are problems in the content as well.

We read in L394-L397: "Figure 13a [..] reveals that the areas that decreased are Water and Evergreen Forest, while Deciduous Forest, Shrubland, Agriculture, Paddy, and Barren increased, with Urban remaining unchanged" This statement is simply not supported by the figure. It seems that 13% of evergreen forest has been replaced by deciduous forests whereas the other LU/LC categories changed insignificantly.

If the area is 13000 km² large then the change indicated in Fig. 13a for "Agriculture" (0.183 %) is 23.79 km² that is not a big area. I would consider this as an insignificant change. The author ERRONEOUSLY states in the abstract that the agricultural area has changed by this factor. This is a serious problem of the paper. I cannot exclude the possibility that I have misunderstood something, but then this would happen to any reader, too. 

It seems that the pixels of the raster data (e.g., Fig. 4) are scaled in latitude/longitude, i.e., in degrees/minutes. If so, it is not clear how the slope values were derived (the vertical unit is meter, of course).

Discussion

The section entitled "Discussions" is not a discussion. The first sentences (mostly irrelevant to a discussion) are a modified repetition of the introduction or the results.

Figures

It is very unique and somewhat disturbing that the ordinate axis of all charts is in logarithmic scale. It is especially misleading in the case of Figs. 12abc; in this case almost all values are in comparable order of magnitude. The really manipulating figure is Fig. 13a and 13c that have odd vertical scales. 

None of the figures have km scale. (The latitude-longitude grid does not replace that as the scale varies with the latitude.)

Fig. 2a: the vertical axis is scaled in mm. It is not clear whether we see a daily, monthly (or other) sum of precipitation. In this case the proper scale would be mm/day or mm/month (or mm/time interval), respectively.

There are typos. Fig. 2b "Precipitaion"

Commonly, mathematical functions (log, exp) are not written in italic (Eqs. (2) and (3)).

It seems that there is an editing problem in L196-L197.

Ref. 28 is empty.

Bottom line

As Geohazards intend to publish new results, my suggestion to the author is to reconsider the manuscript so that the NOVELTY of the paper should be clearly stated. In the current version it is not at all clear to the reviewer.

Author Response

Assessment of Soil Loss Impacts from Land Cover Changes in the Nan River Basin, Thailand

I want to thank the editors and reviewers for their comments and suggestions, which improved the quality of the manuscript. Below, we describe how we have addressed these comments and suggestions and the changes made to the manuscript accordingly. The R text corresponds to our response and paper modifications (PM). PM is reflected in red in the manuscript.

The author tackles the soil loss in the Nan River Basin, Thailand based on land cover changes. This study is based on a widely used (R)USLE method, the author makes estimation on the factors in 2001 and 2019, and compares the two datasets.

The paper has several deficiencies.

The abstract is not satisfying. Formally, it exceeds the allowed length (200 words) by 10%. 

R: The word of the abstract was reduced by approximately 210 words, which might be satisfied.

The sentence "Elevation and slope analyses highlight the vulnerability of elevated and steep terrain to soil erosion" provides no new information, therefore it should not be in the abstract.

R: The sentence was deleted in the revised manuscript.

Content

There are problems in the content as well.

We read in L394-L397: "Figure 13a [..] reveals that the areas that decreased are Water and Evergreen Forest, while Deciduous Forest, Shrubland, Agriculture, Paddy, and Barren increased, with Urban remaining unchanged" This statement is simply not supported by the figure. It seems that 13% of evergreen forest has been replaced by deciduous forests whereas the other LU/LC categories changed insignificantly.

R: I agree with the reviewer that 13% of the evergreen forest has been replaced by deciduous forests, whereas the other LU/LC categories changed insignificantly.

PM: Page 19 lines 435-439.

If the area is 13000 km² large then the change indicated in Fig. 13a for "Agriculture" (0.183 %) is 23.79 km² that is not a big area. I would consider this as an insignificant change. The author ERRONEOUSLY states in the abstract that the agricultural area has changed by this factor. This is a serious problem of the paper. I cannot exclude the possibility that I have misunderstood something, but then this would happen to any reader, too. 

R: The revised manuscript was focused on the change of Deciduous forest and Agriculture.

PM: Page 1 lines 18-20, Page 20 lines 518-523, and Page 20 lines 551-553.

It seems that the pixels of the raster data (e.g., Fig. 4) are scaled in latitude/longitude, i.e., in degrees/minutes. If so, it is not clear how the slope values were derived (the vertical unit is meter, of course).

R: Yes, the coordinates in this study are based on the geospherical coordinate system (latitude in y and longitude in x). The elevation in meters represents the vertical. It can convert latitude and longitude coordinates to distance in meters to calculate the slope. That is basically the geospatial issue of GIS knowledge.

PM: All map figures added the bar scale in km unit.

Discussion

The section entitled "Discussions" is not a discussion. The first sentences (mostly irrelevant to a discussion) are a modified repetition of the introduction or the results.

R: The first sentence was revised.

PM: Page 18 line 458-459.

Figures

It is very unique and somewhat disturbing that the ordinate axis of all charts is in logarithmic scale. It is especially misleading in the case of Figs. 12abc; in this case almost all values are in comparable order of magnitude. The really manipulating figure is Fig. 13a and 13c that have odd vertical scales. 

R: All figures in the bar plot were plotted in the odd vertical scale because it was used to present the change and increase the tendency of difference.

None of the figures have a km scale. (The latitude-longitude grid does not replace that as the scale varies with the latitude.)

R: All map figures added the bar scale in km unit.

Fig. 2a: the vertical axis is scaled in mm. It is not clear whether we see a daily, monthly (or other) sum of precipitation. In this case the proper scale would be mm/day or mm/month (or mm/time interval), respectively.

R: The vertical axis is scaled in mm/month

There are typos. Fig. 2b "Precipitaion"

R: It was changed.

Commonly, mathematical functions (log, exp) are not written in italic (Eqs. (2) and (3)).

R: They were changed.

It seems that there is an editing problem in L196-L197.

R: The problem was removed.

Ref. 28 is empty.

R: It was revised

Bottom line

As Geohazards intend to publish new results, my suggestion to the author is to reconsider the manuscript so that the NOVELTY of the paper should be clearly stated. In the current version it is not at all clear to the reviewer.

R: The originality of this manuscript reveals the impact of the land cover change during 20 years in the Nan River Basin on the soil losses assessment, as the research problem in this study.

Author Response File: Author Response.docx

Reviewer 2 Report

GENERAL COMMENTS

Overall, I believe that the content of this paper deserves consideration for publication on “GeoHazards”. The study evaluates the dynamics of erosion due to soil loss in an area of 13,000 km² of the Nan River Basin (Thailand), using the USLE model, focusing on the impact of changes in land cover. It is a classic topic, addressed by many authors, but the analyzed evolution represents an opportunity to show the correct use of this methodology, applied specifically for the period 2001-2019 thanks to the data collected from several research institutions. As a result, the study provides valuable information for future land management decisions to avoid deviations from unsustainable land use practices that produce notable increases in soil loss rates.

The conclusions are of interest and worthy of publication. The paper is suitably documented and elaborated and, in general, is sufficiently explained.

In my opinion, this study, as conducted, is not exactly a research study. Rather, it is a soil study carried out in a region of Thailand, whose environment may have been affected by excessive development, as the author clearly demonstrates, that induce deterioration in environmental quality and must be stopped.

However, this article cannot be published as is: there are major flaws in the references in the second half of the manuscript; other deficiencies and mistakes in the text must be corrected before publication, including those related to English expression.

MAIN CONCERNS AND QUESTIONS

1-The approach made by the author of the USLE method throughout this article is very positive, perhaps excessively uncritical. Therefore, it may not be objective. For example, this method underwent subsequent improvements due to various observed deficiencies, giving rise to the RUSLE (Revised USLE) and the MUSLE (Modified USLE). I think it is convenient to give a realistic view of the subject, because it always opens the reader's mind and leads to a balanced use.

The USLE not only provides a comprehensive value of the foreseeable soil losses in an area, but also serves, and I consider this to be the case at hand, as a tool to: i) Identify the areas in which the greatest amount of sediment is generated; ii) Identify the causes of soil losses; iii) Implement the most appropriate conservation measures to avoid water erosion.

In this sense, the author is in an ideal position to evaluate his experience, contrasting reality with the calculations made. In any case, it cannot be forgotten that this experience is referred necessarily to the specific environment studied, and cannot be generalized to other areas.

These ideas should be raised in the Introduction or Discussion, because I understand that they constitute the author’s approach to this topic in this paper.

2-Section 2. The author does not explain what tools were used or the procedures followed to obtain the abundant images presented in this article.

3-Section 2.2. I miss some weather data, such as temperature. I consider convenient to add some information in this regard to give a correct overview of the area. Because this area has a monsoon type climate, is advisable to give the range of maximum rainfall due to its likely high incidence on erosion.

4-Section 2.3. It is convenient to indicate some details of the data studied, such as the type of study they come from, analytical methods of the determinations, soil depth studied and number of data available. Likewise, I advise including the distribution of the points studied in Figures 3a and b, and it would also be interesting to write a few words about the rock outcrops, also indicating the type of rocks, because these outcrops have low erosivity.

5-Ls116,118. These “distinct types” (or soil types) are actually “soil textural classes”: it would be more precise to use this terminology. These textural classes are usually applied to soil horizons. Therefore, I think that in L18 it would be more exact write something like: “, the surface horizons of soils in floodplain areas contain ...”.

6-sL127-128. This sentence is confusing. At first sight it seems obvious; or does the author want to classify the soils in the area on this basis? Please, explain better.

7-L196. There are several mistakes: i) this is a new section, and should be written apart; ii) the number of this section must be “2.6 Method of ...”

Additionally, the content of this section is well known in many aspects. Therefore, I suggest writing in the title something similar to “2.6 Method of Estimating Soil Erosion: General Overview and Parameters”.

8-L208. I think the author should introduce some previous commentary in L207-208. For instance, I suggest write something similar to: “The USLE model [24] is based in an empirical parametric equation (1), which mathematically ...rate. This equation is expressed as follows:”.

9-Ls304,311. Both groups of figures (8a,b and 8c,d) represent the result of the factors C and P selected. Because these factors are discretionary (i.e. they are taken at the discretion of the evaluator), it is advisable to weight their observed fit/discrepancy (pros and cons).

10-Ls332-334. There is a jump in the values that evaluate the severity class of the erosion from moderate to severe (there is a void that correspond to the range 10-20 tons/ha/year). If this is not a bug, the author should explain this point and even propose a solution. This may represent a weak point in the selection made due to the dilemma it poses. But if this is not a bug, the author should explain this point and even propose a solution. Why not use the soil erosion severity classes proposed by FAO? A dispersion of criteria on this matter is not advisable: this point should be explained. Please, read the final note of this revision.

11-Section “4. Discussion”. Although the author checks the factors used in the USLE with those obtained by other researchers, it seems convenient to also check the final rates indicated in the text with those obtained by several authors on similar conditions, or with those experimentally obtained in this area.

SPECIFIC COMMENTS

This review does not concern linguistic aspects. Only some cases will be indicated below.

Throughout the text, the author should use similar units in the evaluation of erosion: this can cause confusion in the reader, in addition to being a signal of inconsistency (e.g. Ls38-39,42).

I suggest write values with no more than two decimals to avoid confusion. Additionally, in many of these final values, greater precision does not make sense.

1.-Introduction

As indicated in the caption of manuscript, this paper is signed by one author. However, the text use at least three times the first person of plural (Ls73, 75, 169). Please, revise.

Ls37-38. This statement is obscure: the erosion processes are natural or anthropic, and it is not known if the authors are referring to other phenomena. Please clarify and add references.

2.-Material and Methods

Ls85-86. It is common to write geographical degrees with the abbreviation “º”, as is used in Figure 1. The system that uses “d” sound rare and inconsistent.

L131. We read “the floodplain region”. Please write something similar to “...the soils of the floodplain region...” for reasons of rigor.

Ls143-145. This contribution should be referenced.

Ls152.153. Please, rewrite this sentence. For instance: “The original SRTM data from this study were upscaled to 15 x 15 arc-...”

3.-Results

Please, see above Note 8, that concern Figure 8.

4.-Discussion

Please, see above Note 11.

5.-Conclusion

Ok.

References

The reference list does not have any articles with the DOI code included.

The reference number “28” appears blank in the final list.

The first paragraph of Introduction has accumulated references such as “[1-8]”. Could the author distribute these references throughout this paragraph? Could insert some reference in each statement?

There is confusion of references from the reference [28]: from here on, the insecurity in this aspect is total. These references must be reviewed in depth. Some criteria: the Institutions must be included in this list, as well as the references included in figure captions. The NASA have several Missions or Projects: each one should be a reference.

Ls330,355,370. The references of “Nut et al. [63]” is indicated in the final list as [62]: probably this mistake creeps from the reference number [28]. Please, review thoroughly.

Tables

Table 1: Ok.

Figures

Figure1. Please, include a scale bar in both insets. Please, write in caption “… topography and main drainage network …”

Figure2. I suggest adding “(NASA)” at the end of the first acronym. I also suggest re-writing this sentence of point “a)”: there is redundancy. For instance: “Distribution of monthly average precipitation in the period study 2001-2019”

Figure 3. L161: according to comments and caption, the Figure 3c must be “4c” (flow direction). L163: based on comments and caption, the Figure 3d must be “4d” (flow accumulation). Please, add both the reference number and the name of Institution in the caption.

Figure 4. L156: according to caption of Figure 4, the letter “b” must be “a”. Please, revise and write the corresponding reference number in the caption.

Figure 5. Please, write the corresponding reference number.

Figure 6. Ok.

Figure 7. Ok.

Figure 8. Ok.

Figure 9. Ok.

Figure 10. Ok.

NOTE

One of the most extensively used references in soil erosion classification was proposed by FAO-PNUMA-UNESCO [*]. This classification (Table 1) defined four erosion levels based on soil loss rates computed using the USLE model. Low erosion level was defined for soil loss rates <10 t·ha⁻¹·year⁻¹, whereas very high erosion was established as that occurring at rates >200 t·ha⁻¹·year⁻¹.

[*] FAO-PNUMA-UNESCO: Provisional methodology to evaluate soil erosion. Food and Agricultural Organization of the United Nations, Rome (1980).

Author Response

Assessment of Soil Loss Impacts from Land Cover Changes in the Nan River Basin, Thailand

I want to thank the editors and reviewers for their comments and suggestions, which improved the quality of the manuscript. Below, we describe how we have addressed these comments and suggestions and the changes made to the manuscript accordingly. The R text corresponds to our response and paper modifications (PM). PM is reflected in red in the manuscript.

Comments and Suggestions for Authors

GENERAL COMMENTS

Overall, I believe that the content of this paper deserves consideration for publication on “GeoHazards”. The study evaluates the dynamics of erosion due to soil loss in an area of 13,000 km² of the Nan River Basin (Thailand), using the USLE model, focusing on the impact of changes in land cover. It is a classic topic, addressed by many authors, but the analyzed evolution represents an opportunity to show the correct use of this methodology, applied specifically for the period 2001-2019 thanks to the data collected from several research institutions. As a result, the study provides valuable information for future land management decisions to avoid deviations from unsustainable land use practices that produce notable increases in soil loss rates.

The conclusions are of interest and worthy of publication. The paper is suitably documented and elaborated and, in general, is sufficiently explained.

In my opinion, this study, as conducted, is not exactly a research study. Rather, it is a soil study carried out in a region of Thailand, whose environment may have been affected by excessive development, as the author clearly demonstrates, that induce deterioration in environmental quality and must be stopped.

However, this article cannot be published as is: there are major flaws in the references in the second half of the manuscript; other deficiencies and mistakes in the text must be corrected before publication, including those related to English expression.

 MAIN CONCERNS AND QUESTIONS

1-The approach made by the author of the USLE method throughout this article is very positive, perhaps excessively uncritical. Therefore, it may not be objective. For example, this method underwent subsequent improvements due to various observed deficiencies, giving rise to the RUSLE (Revised USLE) and the MUSLE (Modified USLE). I think it is convenient to give a realistic view of the subject, because it always opens the reader's mind and leads to a balanced use.

The USLE not only provides a comprehensive value of the foreseeable soil losses in an area, but also serves, and I consider this to be the case at hand, as a tool to: i) Identify the areas in which the greatest amount of sediment is generated; ii) Identify the causes of soil losses; iii) Implement the most appropriate conservation measures to avoid water erosion.

In this sense, the author is in an ideal position to evaluate his experience, contrasting reality with the calculations made. In any case, it cannot be forgotten that this experience is referred necessarily to the specific environment studied, and cannot be generalized to other areas.

These ideas should be raised in the Introduction or Discussion, because I understand that they constitute the author’s approach to this topic in this paper.

R: The author's positive stance on the USLE method in the article, while valuable, could benefit from a more balanced and critical perspective. While the USLE is undeniably useful for estimating soil losses and guiding conservation efforts, its subsequent improvements in the form of RUSLE and MUSLE indicate a recognition of certain deficiencies.

It is essential for the author to acknowledge the evolving nature of soil erosion prediction models and the context-specific nature of their findings. The article would be strengthened by discussing the limitations of the USLE method, especially in the Introduction or Discussion sections. This approach would provide readers with a more realistic view, encouraging a nuanced understanding of the method's strengths and weaknesses.

In summary, while the practical utility of the USLE is rightly emphasized, a more objective evaluation that considers both its merits and limitations would enhance the credibility and applicability of the article.

PM: Page 19, line 474-479: It is important to understand that research on soil erosion is context-specific, and findings may not be universally applicable. While this study provides valuable insights into the Upper Nan River Basin, its findings should be considered within the specific environmental context studied. A balanced approach that recognizes the strengths and weaknesses of the USLE method will lead to a more nuanced and applicable understanding of soil erosion dynamics.

2-Section 2. The author does not explain what tools were used or the procedures followed to obtain the abundant images presented in this article.

R: The Python package were used for data analysis and figure generation in this study.

PM: Page 9 Line 234: This study used the Python packages [34] for data analysis and figure generation.

3-Section 2.2. I miss some weather data, such as temperature. I consider convenient to add some information in this regard to give a correct overview of the area. Because this area has a monsoon type climate, is advisable to give the range of maximum rainfall due to its likely high incidence on erosion.

R: The temperature and monsoon in the study area was summarized in page 3-4 line 112-122.

PM: Page 4 line 130-140: The northern region of Thailand experiences seasonal changes in temperature and monsoon activity. From November to March, the area is generally hot and humid, with temperatures ranging from 31-38°C and high relative humidity. The monsoon lows in this area exhibit a cyclonic circulation in the lower troposphere and a warm-cored structure in the upper levels from March to August. The temperature lapse rate in mountainous areas of northern Thailand varies seasonally, with the difference in minimum temperatures changing throughout the year. Floods and soil erosion in the region are caused by a combination of wet catchment conditions, heavy rainfall from monsoonal effects or tropical storms, and the occurrence of El Nino Southern Oscillation events. The temperature and monsoon patterns in the northern area of Thailand are influenced by factors such as the Indian Ocean, the tropical eastern Pacific Ocean, and the high-latitude Asian landmass.

4-Section 2.3. It is convenient to indicate some details of the data studied, such as the type of study they come from, analytical methods of the determinations, soil depth studied and number of data available. Likewise, I advise including the distribution of the points studied in Figures 3a and b, and it would also be interesting to write a few words about the rock outcrops, also indicating the type of rocks, because these outcrops have low erosivity.

R: In this study, the secondary data used is obtained from a data provider, and the soil type information is sourced from government records. The provided data is in raster format, specifying soil texture names along with the percentage of the main soil component (sand, silt, clay). Unfortunately, detailed information about the data, such as the type of study, analytical methods, soil depth, and the number of data points, is not readily available.

5-Ls116,118. These “distinct types” (or soil types) are actually “soil textural classes”: it would be more precise to use this terminology. These textural classes are usually applied to soil horizons. Therefore, I think that in L18 it would be more exact write something like: “, the surface horizons of soils in floodplain areas contain ...”.

R: The sentence was revised based on your suggestion.

PM: Page 5 lines 149-151: On the other hand, the surface horizons of soils in floodplain areas contain eight diverse soil types: silty clay, clay loam, sand clay, sandy loam, silty loam, sand clay loam, loam, and clay.

6-sL127-128. This sentence is confusing. At first sight it seems obvious; or does the author want to classify the soils in the area on this basis? Please, explain better.

R: I am pleased to present a soil classification system that is based on the percentage of three fundamental components, namely sand, silt, and clay. This system is designed to provide a comprehensive and accurate assessment of soil properties, which is essential for various applications in the fields of agriculture, geology, and environmental science.

PM: Page 5 lines 161-161: The classification of soil types in the study area is based on the percentage of three main components: sand, silt, and clay.

7-L196. There are several mistakes: i) this is a new section, and should be written apart; ii) the number of this section must be “2.6 Method of ...”

Additionally, the content of this section is well known in many aspects. Therefore, I suggest writing in the title something similar to “2.6 Method of Estimating Soil Erosion: General Overview and Parameters”.

R: The 2.6 section was added.

PM: 2.6 Method of Estimating Soil Loss

8-L208. I think the author should introduce some previous commentary in L207-208. For instance, I suggest write something similar to: “The USLE model [24] is based in an empirical parametric equation (1), which mathematically ...rate. This equation is expressed as follows:”.

R: I agree with you to change.

PM: The USLE model [24] is based on an empirical parametric Equation (1), which mathematically estimates the average annual soil loss rate. This equation is expressed as follows:

9-Ls304,311. Both groups of figures (8a,b and 8c,d) represent the result of the factors C and P selected. Because these factors are discretionary (i.e. they are taken at the discretion of the evaluator), it is advisable to weight their observed fit/discrepancy (pros and cons).

R: The selection of the C-factor and P-factor was predicated on a prior study, which may have resulted in either underestimation or overestimation. It is imperative to note that the accuracy of the aforementioned factors is contingent upon the reliability of the previous study. Therefore, it is recommended that the results of the current study be interpreted with caution, as the accuracy of the C-factor and P-factor may be compromised.

PM: Page 13-14, Line 351-358: The C-factor and P-factor were identified based on a previous study. It is plausible that the estimation of soil losses in this study may either underestimate or overestimate the actual losses. However, this study employed the change in soil losses to demonstrate the impact of the landcover change. It is important to note that the estimation of soil losses is a complex process that involves several factors, including soil type, slope, and land use. Therefore, the results of this study should be interpreted with caution. Nonetheless, the findings of this study provide valuable insights into the impact of landcover change on soil losses and can be used to inform land management decisions.

10-Ls332-334. There is a jump in the values that evaluate the severity class of the erosion from moderate to severe (there is a void that correspond to the range 10-20 tons/ha/year). If this is not a bug, the author should explain this point and even propose a solution. This may represent a weak point in the selection made due to the dilemma it poses. But if this is not a bug, the author should explain this point and even propose a solution. Why not use the soil erosion severity classes proposed by FAO? A dispersion of criteria on this matter is not advisable: this point should be explained. Please, read the final note of this revision.

R: I wanted to bring to your attention that there is an issue with the manuscript. The revised version added the range of 10-20 tons/ha/year. I took into account the soil erosion with six severity classes as the study area is small. Using the classes identified by FAO, which are meant for large regions, might not allow us to see the difference in soil erosion.

11-Section “4. Discussion”. Although the author checks the factors used in the USLE with those obtained by other researchers, it seems convenient to also check the final rates indicated in the text with those obtained by several authors on similar conditions, or with those experimentally obtained in this area.

R: The discussion was revised to compare with the author research on the similar condition such as Djoukbala, O., Hasbaia, M., Benselama, O., Mazour, M. Comparison of the erosion prediction models from USLE, MUSLE and RUSLE in a Mediterranean watershed, case of Wadi Gazouana (N-W of Algeria). Model. Earth Syst. Environ. 5, 725–743 (2019). Doi: 10.1007/s40808-018-0562-6

PM: Page 20 Lines 493-517: This study presents a study on soil erosion in a distinct geographical area. It is in contrast to the research undertaken in the northwest region of Algeria, which primarily focused on the river basin scale of Wadi Gazouana. Although both studies utilized the Universal Soil Loss Equation (USLE) and its variants, namely the Modified Universal Soil Loss Equation (MUSLE) and the Revised Universal Soil Loss Equation (RUSLE), significant differences emerged in their findings and methodologies. The Algerian study aimed to estimate specific erosion rates in the entire Wadi Ghazouana watershed, given the challenges of water erosion exacerbated by climate change and human intervention [65]. The USLE, RUSLE, and MUSLE models produced erosion rates of 9.65 (t/ha/year), 9.90 (t/ha/year), and 11.33 (t/ha/year), respectively. Of note, the MUSLE model demonstrated a higher spatial dispersion of erosion risk due to the increased effectiveness of the rain factor. These findings offer insights into soil erosion management and mitigation strategies that could be adopted in different regions worldwide.

This study presents an analysis of soil loss rates in a distinct region and highlights a range of erosion rates across severity classes. In particular, the research reveals that the extremely severe class exhibits the highest soil loss rates, with an average of approximately 153.34 tons per hectare per year in 2001 and 138.51 tons per hectare per year in 2019. Conversely, the very low class demonstrates the lowest soil loss rates, averaging around 0.392 tons per hectare per year in 2001 and 0.445 tons per hectare per year in 2019. While both studies offer valuable insights into soil erosion dynamics, the differences in geographic locations, specific methodologies, and the focus on severity classes versus overall erosion rates underscore the complex nature of soil erosion challenges and the importance of customized approaches to address them. The findings highlight the global significance of comprehending and mitigating soil erosion for sustainable land management practices.

SPECIFIC COMMENTS

This review does not concern linguistic aspects. Only some cases will be indicated below.

Throughout the text, the author should use similar units in the evaluation of erosion: this can cause confusion in the reader, in addition to being a signal of inconsistency (e.g. Ls38-39,42).

I suggest write values with no more than two decimals to avoid confusion. Additionally, in many of these final values, greater precision does not make sense.

R: the unit of line 42 was changed to similar to the line 38. 

PM: Line 57 and 60.

1.-Introduction

As indicated in the caption of manuscript, this paper is signed by one author. However, the text use at least three times the first person of plural (Ls73, 75, 169). Please, revise.

R: The texts were revised.

Ls37-38. This statement is obscure: the erosion processes are natural or anthropic, and it is not known if the authors are referring to other phenomena. Please clarify and add references.

 R: The line 37-38 have added the reference.

2.-Material and Methods

Ls85-86. It is common to write geographical degrees with the abbreviation “º”, as is used in Figure 1. The system that uses “d” sound rare and inconsistent.

R: The symbol was changed.

L131. We read “the floodplain region”. Please write something similar to “...the soils of the floodplain region...” for reasons of rigor.

R: The sentence was revised.

Ls143-145. This contribution should be referenced.

R: The detail of this line is explained in Javis et al. [32].

Ls152.153. Please, rewrite this sentence. For instance: “The original SRTM data from this study were upscaled to 15 x 15 arc-...”

R: The sentence was rewritten.

3.-Results

Please, see above Note 8, that concern Figure 8.

R: The narrative of the figure 8 was rewritten.

4.-Discussion

Please, see above Note 11. See answer in comment 11.

5.-Conclusion

Ok.

References

The reference list does not have any articles with the DOI code included.

R: The Doi was added into each reference.

The reference number “28” appears blank in the final list.

R: The number 28 was revised.

The first paragraph of Introduction has accumulated references such as “[1-8]”. Could the author distribute these references throughout this paragraph? Could insert some reference in each statement?

R: The statement for each reference [1-8] was summarized in page 1 lines 38-54.

PM: The Maritsa Basin is currently facing significant soil erosion, which can be attributed to changes in land use and land cover. This issue has been highlighted by studies that have utilized the Revised Universal Soil Loss Equation (RUSLE) [1]. The impact of soil erosion on food production is a major concern, with an annual loss of 10 million hectares of cropland posing a serious threat to global food security [2]. A study on the Lancang-Mekong River basin, which employed RUSLE and GIS techniques, has estimated annual soil erosion rates and identified areas that are vulnerable to increased erosion rates and sediment deposition [3]. A comprehensive review of the (R)USLE model has been conducted, which discusses the model's strengths, limitations, and adaptability to varying conditions. The objective of this review is to improve the model's global applicability and refine soil loss estimates [4]. Predictions of future water erosion rates indicate the influence of socioeconomic development and climate projections [5]. Another study proposes an extension of the Universal Soil Loss Equation (USLE) to predict nitrogen and phosphorus loss during soil erosion [6]. USLE and GIS technology have been utilized in Central Vietnam and Central Chile to assess soil erosion, suggesting targeted solutions and emphasizing the role of vegetative cover in mitigating erosion rates [7, 8]. Overall, these studies underscore the importance of understanding and addressing soil erosion for sustainable land use and conservation efforts globally.

There is confusion of references from the reference [28]: from here on, the insecurity in this aspect is total. These references must be reviewed in depth. Some criteria: the Institutions must be included in this list, as well as the references included in figure captions. The NASA have several Missions or Projects: each one should be a reference.

R: The number 28 is the Mission that has mission in Line 103.

Ls330,355,370. The references of “Nut et al. [63]” is indicated in the final list as [62]: probably this mistake creeps from the reference number [28]. Please, review thoroughly.

R: The number of references was rerun, and the Nut et al. [63] is the number of 63.

Tables

Table 1: Ok.

Figures

Figure1. Please, include a scale bar in both insets. Please, write in caption “… topography and main drainage network …”

R: The scale bar was added in each map. Figure 1, 2, 3, 4, 5, 7, 8, and 9.

Figure2. I suggest adding “(NASA)” at the end of the first acronym. I also suggest re-writing this sentence of point “a)”: there is redundancy. For instance: “Distribution of monthly average precipitation in the period study 2001-2019”

R: The sentence was revised.

Figure 3. L161: according to comments and caption, the Figure 3c must be “4c” (flow direction). L163: based on comments and caption, the Figure 3d must be “4d” (flow accumulation). Please, add both the reference number and the name of Institution in the caption.

R: The sentences were revised.

Figure 4. L156: according to caption of Figure 4, the letter “b” must be “a”. Please, revise and write the corresponding reference number in the caption.

R: The Figure a and b were mentioned in the manuscript.

Figure 5. Please, write the corresponding reference number.

R: The Figure 5a, 5b, and 5c were referred in the manuscript lines 200-210. 

Figure 6. Ok.

Figure 7. Ok.

Figure 8. Ok.

Figure 9. Ok.

Figure 10. Ok.

NOTE

One of the most extensively used references in soil erosion classification was proposed by FAO-PNUMA-UNESCO [*]. This classification (Table 1) defined four erosion levels based on soil loss rates computed using the USLE model. Low erosion level was defined for soil loss rates <10 t·ha⁻¹·year⁻¹, whereas very high erosion was established as that occurring at rates >200 t·ha⁻¹·year⁻¹.

[*] FAO-PNUMA-UNESCO: Provisional methodology to evaluate soil erosion. Food and Agricultural Organization of the United Nations, Rome (1980).

R: The mentioned reference was added into the revised manuscript.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments for author File: Comments.pdf

Author Response

Review Comments on the manuscript:

Assessment of Soil Loss Impacts from Land Cover Changes in the Nan River Basin, Thailand

I want to thank the editors and reviewers for their comments and suggestions, which improved the quality of the manuscript. Below, we describe how we have addressed these comments and suggestions and the changes made to the manuscript accordingly. The R text corresponds to our response and paper modifications (PM). PM is reflected in red in the manuscript.

The comprehensive analysis sheds light on the intricate dynamics of soil erosion in the Nan River Basin, Thailand, emphasizing the significant impact of land cover changes on soil loss. The study employed the Universal Soil Loss Equation (USLE) model, integrating key factors such as rainfall erosivity, soil erodibility, topography, crop management, and conservation practices to estimate soil loss rates. The results revealed spatial variations in the distribution of factors, with higher rainfall erosivity in the northern region, concentrated soil erodibility in the floodplain, and notable differences in topography influencing the LS factor. Generally, the paper has reasonable structure and clear results, but there are few minor shortcomings in the paper that need to be revised. Comments and suggestions are as follows:

1. [P2, L85 & 86] d is wrong. Use the symbol of degree as '°' rather than'd'.

R: The degree symbol changed from ‘d’ to ‘°’ based on your recommendation.

PM: Please see in the manuscript page 3, lines 104-105 in the blue.

2. [P5, Figure 3 a) & b)] In general, sandstone contains less organic carbon as compared to clayey or loamy soil, then how sandstone abundant area has high percentage of organic carbon in Figure 3? Justify.

R: The % organic carbon was decreased for the sandstone type, as shown in Figure 3b.

PM: Figure 3b on page 6.

3. [P1, L15, 16 &17] How the approximate values in abstract change into the observed accurate values in conclusion [P18, L478 & 479] ? Keep the clear rationale.

R: The landcover change in this manuscript was based on the satellite image from the MODIS sensor. Then, I changed the manuscript to relate the landcover change due to the MODIS.

PM: Page 20, lines 552-554: The satellite image (MODIS) showed the increase in Agriculture of 13.2% and the corresponding decrease in Evergreen Forest of 13.7% and Water of 0.125% cover types highlight the anthropogenic footprint on the landscape.

4. [P17, L413 Figure 13 a)] Keep suitable space between paragraph and figures.

R: The space between figure 13a and text was increased.

5. [P4, L115] LDD has been cited on Reference 31 instead of 30 which needs to be corrected and Reference number 30 is seen missing to be cited in text

R: I have checked the number of the reference and rerun again that the LDD is a number of 30.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

FINAL NOTES TO THIS REVISION

I have carefully read the author’s comments. I note that he has followed almost all my instructions, which were aimed to improve the content of this paper. Following this line, I want to end my review by indicating a couple of small formal improvements such as the following, already indicated in my previous review:

a) I suggest write values with no more than two decimals to avoid confusion. Additionally, in many of these final values, greater precision does not make sense. E.g., those you have highlighted in red color in sections 3.2, 3.3, 3.4 and some of section 4. In this sense, the inconsistency persists.

b) Finally, please, revise the use of the first person of plural in Ls92.

Author Response

Review Comments on the manuscript:

Assessment of Soil Loss Impacts from Land Cover Changes in the Nan River Basin, Thailand

I want to thank the editors and reviewers for their comments and suggestions, which improved the quality of the manuscript. Below, the author would like to describe how we have addressed these comments and suggestions and the changes made to the manuscript. The R text corresponds to our response, and the manuscript's paper modifications are in blue.

I have carefully read the author’s comments. I note that he has followed almost all my instructions, which were aimed to improve the content of this paper. Following this line, I want to end my review by indicating a couple of small formal improvements such as the following, already indicated in my previous review:

a) I suggest write values with no more than two decimals to avoid confusion. Additionally, in many of these final values, greater precision does not make sense. E.g., those you have highlighted in red color in sections 3.2, 3.3, 3.4 and some of section 4. In this sense, the inconsistency persists.

R: The values of all results have been modified to include two decimal places in sections 3.2, 3.3, 3.4, and 4. Additionally, Figures 10, 11, 12, and 13 have been updated to include the two decimal places for presenting the results.

b) Finally, please, revise the use of the first person of plural in Ls92.

R: Line 92, the pronouns "we" and "our" were changed to first-person."