Soil Erosion Assessment Using the RUSLE Model and Geospatial Techniques (Remote Sensing and GIS) in South-Central Niger (Maradi Region)

Round 1

Reviewer 1 Report

Review of the manuscript entitled " Soil erosion assessment using the RUSLE model and Geospatial techniques (Remote Sensing and GIS) in South-Central Niger (Maradi region)"

General comments: In this paper, the authors examined the revised Universal Soil Loss Equation model (RUSLE) and Remote Sensing and Geographic Information System (GIS) techniques were used to estimate soil erosion risk in the Maradi region of the south-central Niger. The spatial trend of seasonal soil erosion was obtained by integrating remote sensing environmental variables in a grid-based GIS method. Based on RUSLE, the result findings showed an estimated potential mean annual soil loss of 472.4 t/ac/. The potential erosion rates varied from 14.8 to 944.9 t/ac/yr. Also, the most eroded area was central and west-southern areas, with erosion rates ranging from 237.1 to 944.9 t/ac/yr.

My opinion: Soil erosion is a serious problem arising from anthropogenic activities such as agricultural intensification, land degradation, etc. the author (s) utilize the RUSLE model with remote sensing and GIS to estimate soil erosion risk in the Maradi region of the south-central Niger. In general, the RUSLE model performed quite well and can be used as a reference predictive tool for deriving land planning and management strategies in south-central Niger. Overall, this manuscript improves our understanding of interactions between land use management, land cover, and topographical properties of the landscape are important to effectively control soil erosion. The manuscript is good and well written. The authors have highlighted some important considerations and the manuscript has the potential to be published. However, I have major concerns about some aspects of the manuscript that the authors need to carefully clarify or fixed the queries raised in the Table attached.

Comments for author File: Comments.pdf

Author Response

Response to Reviewer 1 Comments

 

Point 1: General comments: In this paper, the authors examined the revised Universal Soil Loss Equation model (RUSLE) and Remote Sensing and Geographic Information System (GIS) techniques were used to estimate soil erosion risk in the Maradi region of the south-central Niger. The spatial trend of seasonal soil erosion was obtained by integrating remote sensing environmental variables in a grid-based GIS method. Based on RUSLE, the result findings showed an estimated potential mean annual soil loss of 472.4 t/ac/. The potential erosion rates varied from 14.8 to 944.9 t/ac/yr. Also, the most eroded area was central and west-southern areas, with erosion rates ranging from 237.1 to 944.9 t/ac/yr.

 

Response 1: thank you very much

Point 2: My  opinion:  Soil  erosion  is  a  serious  problem  arising  from  anthropogenic  activities  such  as  agricultural intensification, land degradation, etc. the author (s) utilize the RUSLE model with remote sensing and GIS to estimate soil erosion risk in the Maradi region of the south-central Niger. In general, the RUSLE model performed  quite  well  and  can  be  used  as  a  reference  predictive  tool  for  deriving  land  planning  and management  strategies  in  south-central  Niger.  Overall, this manuscript improves our understanding of interactions between land use management, land cover, and topographical properties of the landscape are important to effectively control soil erosion. The manuscript is good and well written. The authors have highlighted some important considerations and the manuscript has the potential to be published. However, I have major concerns about some aspects of the manuscript that the authors need to carefully clarify or fixed the queries raised in the Table below.

 

Response 2: Thank you for reminding us how good and well written the manuscript it is in generally interesting and well explained. We are grateful to the reviewer for these kind observations.

The points to consider are summarized in the table below:

 

Point 1: a)    Title:	Overall, the title is appropriate for the paper.
Response 1:  Thank you for your kind suggestion.
Point 2: b)   Abstract:	Overall, the abstract is well-written and informative.
Response 2: Thank you so much for this excellent observation.
Point 3: c)   Keywords:	The authors provided three (3) keywords. The keywords are appropriate and keywords. Although, it is within the journal's specified number, I suggest the authors  can  add  three  additional  keywords  to  improve  the  article  search results  in  the  future  or  increase  the  article's  visibility  to  a  large  search  by readers.
Response 3: Thank you very much for your nice reminder that helped us improve this manuscript. We added the following keywords to improve  the  article  search results: Land use change, climatic zones, Maradi Region,
Point 4: d)    Abbreviations	Abbreviations are largely defined at first use
Response 4: Thank you for pointing this out! We found your comments extremely helpful and have revised accordingly.
Point 5 : e)  Introduction	The  authors  provided  provide  useful  information  for  the  readers  in  this section. The significance of the study is concise and clearly stated. However, I recommend authors improve the flow of this section. Most of the sentence structure is too long. I suggest the authors split sentences. Also, the authors include more recent literatures. This section needs a minor English language editing. Minor comments Line 62: change “to” with “in” to read “… factor in reservoirs.” Line 64: delete “all”
Response 5: We very much appreciate reviewer’s suggestion and we have improved this section and most of the sentence structure have split in the revised manuscript. We also updated literature review with addition of recent publications. And finally, the English language have edited to improve the article. Hopefully now you will find it rational.   We have changed “to” with “in” to read “… factor in reservoirs.” Line 62. And deleted “all” Line 64 in the revised manuscript
Point 6: f)     Materials     and Methods	the  methodology  section  is  clear,  transparent,  and  is  appropriate  for  this study.  The research procedures and techniques used are standard and reproducible.  The author (s) should clearly state the study limitation(s) or challenges encountered. Last but not least, I suggest minor language editing to improve the manuscript. Minor comments Line 207: insert “the” to read “in the Maradi region …” Line  229:  insert  “the”  to  read  “…  soil  to  the  isolation  and  transfer  of  soil particles.”
Response 6: Thank you so much for your suggestion. Yes, we have edited the language to improve the manuscript for better understanding. Hopefully you will find it logical.   We have inserted “the” to read “in the Maradi region …” Line 207. And have inserted  “the”  to  read  “…  soil  to  the  isolation  and  transfer  of  soil particles.” Line 229. In the revised manuscript.
Point 7: g)    Results and Discussion	The results are well presented and complemented with figures that helped in results    visualization.  However, some information presented    needs clarifications.  For example, most of the sentence structure is too long.  I suggest the authors split sentences for many of the long sentences. Also, I did authors should improve the discussion of the results. Last but not least, I suggest minor language editing to improve the manuscript.
Response 7: Thank you so much for your precious comments. The results and Discussion section is thoroughly revised considering your valuable suggestion in the revised manuscript. Hopefully you will find it justified.
Point 8: h)    Conclusion	The conclusion section is well written and supports the findings. However, I think minor language editing is needed to improve this section.
Response 8: Thank you so much for your comments. The section is corrected in the revised version.
Point 9: Recommendation	Accept with minor revision
Response 9: We very much appreciate the reviewer’s detailed evaluations and suggestions.  We  agree  with  most  of  them,  and  the  manuscript  has  been  revised thoroughly  according  to  the  reviewer’s  advice.

 

Author Response File: Author Response.pdf

Reviewer 2 Report

The work was carried out using ordinary approaches and methods that are now very fashionable in similar studies worldwide. In this regard, the authors did not bring anything new to science. As for the results obtained, their discussion is poor.

1. Any model requires verification by independent methods, at least in part. This is a feasible task for modeling soil erosion. According to Conclusions, the authors consider their findings to be actual and do not require proof. Your results will remain speculation until they find confirmation in alternative approaches. This can be data from field studies both in your region and adjacent regions with similar environmental conditions. The authors did not even attempt to find any confirmation of their findings. This is a significant flaw in their research. The authors should carefully consider this issue.
2. With such a diverse set of factors that determine soil erosion intensity, according to the maps obtained, the final map (Figure 8) shows an almost universal prevalence of low soil erosion. Separate small areas of increased erosion are confined, as a rule, to river valleys and are most likely associated with steeper slopes. The spatial analysis in the manuscript is inferior. This is the second major flaw in the study.
3. The manuscript is missing a section on the limitations and uncertainties of your research. The authors should be more critical of their results.
4. What are the practical recommendations from your research?

Additional comments:

1. What is “Soil loss erosion”? There are “Soil loss” and “Soil erosion,” but Soil loss erosion… It is strange.
2. Line 142-143. “… soils characterized by their dune character (Sandy, sandy-loam and alluvial).” It is an incorrect phrase in which the authors illogically mixed geomorphology and geology with soils.
3. Figure 1. The scale of the bottom left-hand map is incorrect.
4. Line 166. What is "Drilling erosion on floodplains"?
5. Table 3. Fotest?
6. Lines 274-278. I didn't quite understand how you calculated the P-index for your study.
7. Figure 3. Is the scale of the left-hand map correct? It seems to me not.
8. Figure 5. What are the slope units on the left-hand map? How can such large values of slopes (close to vertical) prevail over the study area???
9. Figure 6. The right-hand map legend does not match the color palette of the map itself. This makes the map very difficult to read.
10. Lines 354-356. “Moreover, the greater the importance of conservation measures, the greater the susceptibility of the soil to erosion”. Maybe just the opposite? “Moreover, the greater the susceptibility of the soil to erosion, the greater the importance of measures”. The same goes for the following sentence.

The manuscript requires significant improvement. I cannot recommend it for publication in its current form.

Author Response

Response to Reviewer 2 Comments

The work was carried out using ordinary approaches and methods that are now very fashionable in similar studies worldwide. In this regard, the authors did not bring anything new to science. As for the results obtained, their discussion is poor.

Point 1: Any model requires verification by independent methods, at least in part. This is a feasible task for modelling soil erosion. According to Conclusions, the authors consider their findings to be actual and do not require proof. Your results will remain speculation until they find confirmation in alternative approaches. This can be data from field studies both in your region and adjacent regions with similar environmental conditions. The authors did not even attempt to find any confirmation of their findings. This is a significant flaw in their research. The authors should carefully consider this issue.

 

Response 1: Thank you so much for your minute observation and valuable comments. We have taken the reviewer’s comment into full consideration and it will be well reflected by the revised version of the manuscript.

 

Point 2: With such a diverse set of factors that determine soil erosion intensity, according to the maps obtained, the final map (Figure 8) shows an almost universal prevalence of low soil erosion. Separate small areas of increased erosion are confined, as a rule, to river valleys and are most likely associated with steeper slopes. The spatial analysis in the manuscript is inferior. This is the second major flaw in the study.

 

Response 2: Thank you very much for your valuable suggestion. However, our research was used to estimate soil erosion potential and potential zone in the Maradi region of the south-central Niger. The spatial trend of seasonal soil erosion was obtained by integrating remote sensing environmental variables in a grid-based GIS method. This section with the final map (Figure 8) is thoroughly revised considering your valuable suggestion. Hopefully, you will find it justified

 

Point 3: The manuscript is missing a section on the limitations and uncertainties of your research. The authors should be more critical of their results.

 

Response 3: We have taken the reviewer’s comment into full consideration. A whole new paragraph mentioning the Approach of limitations and uncertainties is added in section 2.3 in the revised manuscript thoroughly according to the reviewer’s advice.

 

Point 4: What are the practical recommendations from your research?

 

Response 4: Thank you for pointing this out. The reviewer is correct, and we have addressed the practical recommendations during the revision of the manuscript in conclusion section 4. Hopefully, you will find it logical

Additional comments:

Point 1: What is “Soil loss erosion”? There are “Soil loss” and “Soil erosion,” but Soil loss erosion… It is strange

Response 1: Thank you so much for your comments and suggestion. The reviewer is correct, this is a mistake and strange to find “Soil loss erosion”, which is now been rectified. This point is revised accordingly and hopefully, you will find it justified.

 

Point 2: Line 142-143. “… soils characterized by their dune character (Sandy, sandy-loam and alluvial).” It is an incorrect phrase in which the authors illogically mixed geomorphology and geology with soils.

 

Response 2: Thank you so much for your comments. We agree with your suggestion. Therefore, kindly note that in this study, this line 142-143 is mentioned here, mainly giving a briefing about the description of the study area for better understanding. Also from our belief, this is not illogically mixed anywhere else.

 

Point 3: Figure 1. The scale of the bottom left-hand map is incorrect.

 

Response 3: Thank you so much for your comment. Yes, now Figure 1. The scale of the bottom left-hand map is corrected in the revised manuscript for better representation.

Point 4: Line 166. What is "Drilling erosion on floodplains"?

 

Response 4: Thank you so much for your comments. This sentence is restructured to make it more clearly for the reader. And we have replaced it with another sentence in the revised manuscript.

 

Point 5: Table 3. Fotest?

Response 5: Thank you so much for your comments. The mistake in Table 3. Is corrected in the revised version.

 

Point 6: Lines 274-278. I didn't quite understand how you calculated the P-index for your study.

Response 6: Thank you so much for your important comment. The P index was calculated using the land use types and slope gradients present in the research region, which were taken into account while evaluating the RUSLE's P-value.

 

Point 7: Figure 3. Is the scale of the left-hand map correct? It seems to me not.

Response 7: Thank you so much for your comment. Yes, now Figure 3. The scale of the left-hand map is corrected in the revised manuscript for better representation

Point 8: Figure 5. What are the slope units on the left-hand map? How can such large values of slopes (close to vertical) prevail over the study area???

Response 8: Thank you so much for your suggestion. In Figure 5 the slope units on the left-hand map are in percentage. And then, such large values of slopes (close to vertical) can prevail over the study area, as the most significant and critical characteristic affecting landslide vulnerability is the slope. The slope values most essential quality is that they can be simply generated and studied from digital elevation model (DEM) data using geographic information system (GIS) applications, as well as easily plotted.

Point 9: Figure 6. The right-hand map legend does not match the color palette of the map itself. This makes the map very difficult to read.

 

Response 9: Thank you so much for your suggestion. Now Figure 6. The right-hand map legend is revised for better representation. Hopefully, you will find it logical.

 

Point 10: Lines 354-356. “Moreover, the greater the importance of conservation measures, the greater the susceptibility of the soil to erosion”. Maybe just the opposite? “Moreover, the greater the susceptibility of the soil to erosion, the greater the importance of measures”. The same goes for the following sentence.

 

Response 10: Thank you so much for your suggestion. The whole sentence is significantly revised to make it more clear for the reader in the revised manuscript thoroughly according to the reviewer’s advice.

 

 

 

Author Response File: Author Response.pdf

Reviewer 3 Report

This is a numerical exercise of soil erosion estimation. The reviewer thanks to the revision of the manuscript. Basically, this result may be beneficial for the people in the target area, and can be used as a good reference for future decision making. However, the following points are not cleared yet.

1) As for the Reviewer comment 3, the discussion on the validation of the results is still missing. The meaning of the "validation" is , how to confirm the calculated values are appropriate. For example, figure 8 is the main result of the study. Although I do not wonder the calculation scheme and equations, factors used in the study, the discussion on whether the obtained results are reasonable or not is quite important issue. Scientific approach usually needs the idea of "validation" of the results.

2) As for the reviewer 1 comment 6, there is no corresponding explanation. The distribution of rainfall shown in (a) is not uniform (some points are dark blue and other point are almost white, and these are not in gradation). The R factor was obtained by equation (2), and it only depends on this rainfall. However, the distribution of R in (b) is very smooth gradation. That's strange.

In addition, using P as rainfall in equation (2) makes confusion on P factor in equation (1)

3) As for the reviewer 1 comment 6, although this is not mandatory to be corrected, the explanation of FA shall be in the text of the paper, not only in the answer to the reviewer.

 

 

Author Response

Response to Reviewer 3 Comments

This is a numerical exercise of soil erosion estimation. The reviewer thanks to the revision of the manuscript. Basically, this result may be beneficial for the people in the target area, and can be used as a good reference for future decision making. However, the following points are not cleared yet.

Response: Thank you so much for your valuable comments and suggestions.

Point 1:  As for the Reviewer comment 3, the discussion on the validation of the results is still missing. The meaning of the "validation" is , how to confirm the calculated values are appropriate. For example, figure 8 is the main result of the study. Although I do not wonder the calculation scheme and equations, factors used in the study, the discussion on whether the obtained results are reasonable or not is quite important issue. Scientific approach usually needs the idea of "validation" of the results.

Response 1: Thank you for this excellent suggestion. Yes, we have made the discussion on the validation of the main results of the study.  Therefore, this validation was accomplished via the use of the RUSLE model in conjunction with local perspectives. As input parameters, soil, land use/cover, DEM, rainfall, and support practise data were employed. The raster layers were processed to display the relevant input parameters on the ArcGIS platform, and the inputs were then multiplied to calculate the yearly average rate of soil loss and create intensity maps for the research area. Hopefully you will find it logical

 

Point 2: As for the reviewer 1 comment 6, there is no corresponding explanation. The distribution of rainfall shown in (a) is not uniform (some points are dark blue and other point are almost white, and these are not in gradation). The R factor was obtained by equation (2), and it only depends on this rainfall. However, the distribution of R in (b) is very smooth gradation. That's strange.

In addition, using P as rainfall in equation (2) makes confusion on P factor in equation (1)

Response 2: Thank you so much for your comment. Yes, now the distribution of rainfall shown in (a) is corrected in the revised manuscript for better representation.

Furthermore, using P as rainfall in equation (2) has been used since Renard and Freimund (1994) equation, which establishes a relationship between (R) and yearly average rainfall (P). Hopefully you will find it justified.

 

Point 3: As for the reviewer 1 comment 6, although this is not mandatory to be corrected, the explanation of FA shall be in the text of the paper, not only in the answer to the reviewer.

Response 3: Thank you so much for your precious suggestion. We have included a detailed description of FA in the text paper's section 2.2 Data Source processing, Slope length and steepness (LS-factor) section; thoroughly according to the reviewer’s advice.

 

The explanation of FA in the text of the paper are as follows: FA are obtained as flowing by calculating the flow direction win DEM. To each cell, the flow accumulation is determined by how many cells that flows through that cell; if the flow accumulation value is greater, the area will be easier to form a runoff.

 

Author Response File: Author Response.pdf

Reviewer 4 Report

Dear Editor.

I have studied the responses that authors provided, according to my and the other reviewers comments. I believe that the paper is significantly improved. However, I have some minor comments to add.

1. The authors should check again the manuscript in order to correct some minor text errors. For example, in table 3 the word "Fotest" is wrong.
2.  I think that there is enough space in order the figures to be larger. Also, the MPDI do not have limitations to pages, so you can enlarge the figures.
3. Lines 352-353. I asked the authors to discuss the limitations of the their methodology. But I did not find where is this discussion. Please, explain which are the limitation of the methodology.

I do not have any other comments.

Author Response

Response to Reviewer 3 Comments

This is a numerical exercise of soil erosion estimation. The reviewer thanks to the revision of the manuscript. Basically, this result may be beneficial for the people in the target area, and can be used as a good reference for future decision making. However, the following points are not cleared yet.

Response: Thank you so much for your valuable comments and suggestions.

Point 1:  As for the Reviewer comment 3, the discussion on the validation of the results is still missing. The meaning of the "validation" is , how to confirm the calculated values are appropriate. For example, figure 8 is the main result of the study. Although I do not wonder the calculation scheme and equations, factors used in the study, the discussion on whether the obtained results are reasonable or not is quite important issue. Scientific approach usually needs the idea of "validation" of the results.

Response 1: Thank you for this excellent suggestion. Yes, we have made the discussion on the validation of the main results of the study.  Therefore, this validation was accomplished via the use of the RUSLE model in conjunction with local perspectives. As input parameters, soil, land use/cover, DEM, rainfall, and support practise data were employed. The raster layers were processed to display the relevant input parameters on the ArcGIS platform, and the inputs were then multiplied to calculate the yearly average rate of soil loss and create intensity maps for the research area. Hopefully you will find it logical

 

Point 2: As for the reviewer 1 comment 6, there is no corresponding explanation. The distribution of rainfall shown in (a) is not uniform (some points are dark blue and other point are almost white, and these are not in gradation). The R factor was obtained by equation (2), and it only depends on this rainfall. However, the distribution of R in (b) is very smooth gradation. That's strange.

In addition, using P as rainfall in equation (2) makes confusion on P factor in equation (1)

Response 2: Thank you so much for your comment. Yes, now the distribution of rainfall shown in (a) is corrected in the revised manuscript for better representation.

Furthermore, using P as rainfall in equation (2) has been used since Renard and Freimund (1994) equation, which establishes a relationship between (R) and yearly average rainfall (P). Hopefully you will find it justified.

 

Point 3: As for the reviewer 1 comment 6, although this is not mandatory to be corrected, the explanation of FA shall be in the text of the paper, not only in the answer to the reviewer.

Response 3: Thank you so much for your precious suggestion. We have included a detailed description of FA in the text paper's section 2.2 Data Source processing, Slope length and steepness (LS-factor) section; thoroughly according to the reviewer’s advice.

 

The explanation of FA in the text of the paper are as follows: FA are obtained as flowing by calculating the flow direction win DEM. To each cell, the flow accumulation is determined by how many cells that flows through that cell; if the flow accumulation value is greater, the area will be easier to form a runoff.

 

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

1. Although the authors took into account many of my recommendations, my crucial question remained unanswered. I repeat it:

“Any model requires verification by independent methods, at least in part. This is a feasible task for modeling soil erosion. According to Conclusions, the authors consider their findings to be actual and do not require proof. Your results will remain speculation until they find confirmation in alternative approaches. This can be data from field studies both in your region and adjacent regions with similar environmental conditions. The authors did not even attempt to find any confirmation of their findings. This is a significant flaw in their research. The authors should carefully consider this issue.”

In this regard, the Discussion section is poor from the point of view of discussing the obtained model results with international experience. In its current form, the manuscript looks more like a report than a scientific work.

2. I am still puzzled by the left map of Figure 5. Within the study area, slopes of 89-90% are highly (almost wholly) dominant. In terms of degrees, this is about 42° (degrees). But such slopes are most typical for mid-mountainous and high-mountain regions. How is this possible for a vast plain territory (41,144 sq. km), where the elevation difference is just over 200 m (see Figure 1)?

In addition:

1. I am again surprised by the phrase (corrected in the revised manuscript): "... with dune-like soils (Sandy, sandy-loam and alluvial)." This is the first time I have seen it. There are dune soils (soils on dunes) but not dune-like soils! Moreover, "alluvial" is not a granulometric fraction but a genetic characteristic (alluvial, colluvial, proluvial, aeolian, etc.). Consult a soil scientist for the correct writing of this part of the section.
2.  2.3. Approaches for the limitations and uncertainties of model results. Why “Approaches”? There are simply limitations and uncertainties. It is enough.
3. The authors again did not take into account my previous remark. Lines 404-406. “Moreover, the greater the importance of conservation measures, the greater the susceptibility of the soil to erosion; the lower the values of conservation measures, the lower the susceptibility of the soil to erosion.” Why are you swapping cause and effect (consequence)? Does the wind blow because the tree sways, or does the tree sway because the wind blows?

Dear Authors, I am making these comments for the last time. If my above remarks are not considered or logically reasoned in the re-revised manuscript, I will recommend rejecting your manuscript.

Author Response

We would like to thank the reviewer for the thorough review of our manuscript, the encouraging words, and helpful comments. We have addressed all comments as suggested by the reviewers in our manuscript, as indicated below.

 

Point 1: Although the authors took into account many of my recommendations, my crucial question remained unanswered. I repeat it:

“Any model requires verification by independent methods, at least in part. This is a feasible task for modeling soil erosion. According to Conclusions, the authors consider their findings to be actual and do not require proof. Your results will remain speculation until they find confirmation in alternative approaches. This can be data from field studies both in your region and adjacent regions with similar environmental conditions. The authors did not even attempt to find any confirmation of their findings. This is a significant flaw in their research. The authors should carefully consider this issue.”

In this regard, the Discussion section is poor from the point of view of discussing the obtained model results with international experience. In its current form, the manuscript looks more like a report than a scientific work.

Response 1: Thank you so much for your comments. This issue was carefully considered in section 3.2 Estimating of potential soil erosion. Kindly see the conclusion which is fully revised and as well as the discussion section in the revised manuscript. Also based on your suggestion, we have also updated our conclusion, which we considered the results of our analysis, by summarizing the main points of our research and connecting the significance or results of the main points. Hopefully you will find it justified.

Point 2: I am still puzzled by the left map of Figure 5. Within the study area, slopes of 89-90% are highly (almost wholly) dominant. In terms of degrees, this is about 42° (degrees). But such slopes are most typical for mid-mountainous and high-mountain regions. How is this possible for a vast plain territory (41,144 sq. km), where the elevation difference is just over 200 m (see Figure 1)?

Response 2: Thank you very much for your valuable suggestion. Sorry for mentioned slope % in the left map of Figure 5. I rechecked the manuscript and just found a simple mistake in Figure 5a, which is now been rectified, and have replaced with new figure in Degree with better understanding. Hopefully you will find it justified.

In addition:

Point 1: I am again surprised by the phrase (corrected in the revised manuscript): "... with dune-like soils (Sandy, sandy-loam and alluvial)." This is the first time I have seen it. There are dune soils (soils on dunes) but not dune-like soils! Moreover, "alluvial" is not a granulometric fraction but a genetic characteristic (alluvial, colluvial, proluvial, aeolian, etc.). Consult a soil scientist for the correct writing of this part of the section.

 

Response 1: Thank you very much for pointing this out. "... with dune-like soils (Sandy, sandy-loam and alluvial)." And "alluvial" has been removed. As suggested the reviewer, we have revised the sentence as follows: "… with dune soils (Soils on dunes)." In the revised manuscript.

 

Point 2: Approaches for the limitations and uncertainties of model results. Why “Approaches”? There are simply limitations and uncertainties. It is enough.

 

Response 2: Thank you so much for your comment. We totally agree with your suggestion. We have removed “Approaches” and revised the sentence as follows: “Limitations and uncertainties” in section 2.3.

 

Point 3: The authors again did not take into account my previous remark. Lines 404-406. “Moreover, the greater the importance of conservation measures, the greater the susceptibility of the soil to erosion; the lower the values of conservation measures, the lower the susceptibility of the soil to erosion.” Why are you swapping cause and effect (consequence)? Does the wind blow because the tree sways, or does the tree sway because the wind blows?

 

Response 3: Thank you so much for your kind suggestion. The sentence in Lines 404-406 is restructured to make it more clear for the reader. We have revised the sentence as follows: “Besides, the relevance of conservation measures increases soil erosion vulnerability.” Yes, the tree sways because the wind blows.

 

 

Author Response File: Author Response.pdf

Round 3

Reviewer 2 Report

Figure 5. The modified legend made your map (5a) even more unrealistic. In nature, it cannot be that slopes with a steepness of almost 90 degrees prevail over more than 90% of the area of a large (especially plain) basin! Sorry, but this is absurd. I can only assume that the ends of the legend are turned upside down by mistake. Most likely, gentle slopes (first degrees) prevail, and very steep slopes are very rare. This is a common occurrence in lowland/plain river basins. If this is not a mistake, such slopes lead to a big error in calculating the potential soil erosion. Authors should carefully re-check the correctness of the calculation of the slopes of the studied basin.

Author Response

We would like to thank the reviewer for the thorough review of our manuscript, the encouraging words, the helpful comments, and the opportunity to resubmit the revised copy of our manuscript: ID: water-1423699. We have addressed all comments as suggested by the reviewer in our manuscript. As indicated below.

 

Point 1: Figure 5. The modified legend made your map (5a) even more unrealistic. In nature, it cannot be that slopes with a steepness of almost 90 degrees prevail over more than 90% of the area of a large (especially plain) basin! Sorry, but this is absurd. I can only assume that the ends of the legend are turned upside down by mistake. Most likely, gentle slopes (first degrees) prevail, and very steep slopes are very rare. This is a common occurrence in lowland/plain river basins. If this is not a mistake, such slopes lead to a big error in calculating the potential soil erosion. Authors should carefully re-check the correctness of the calculation of the slopes of the studied basin.

 

Response 1: Thank you so much for your comments. Yes, you’re right. I rechecked the manuscript and just found a mistake in Figure 5a legend, which is more unrealistic. Now, this mistake has been rectified and has been replaced with a new figure legend in Degree with a better understanding. Furthermore, slope maps highlight the regions with high potential runoff and then high erosion rate; these potentials are decreases from high slope degree to lower slope degree. Hopefully, you will find it justified.

Author Response File: Author Response.pdf

Round 4

Reviewer 2 Report

In the revised version of the manuscript, I have not found any changes to the map in Figure 5a. Slopes close to 90 degrees still dominate there almost everywhere. This is extremely strange for a large river basin (about 42 thousand square kilometers), where the elevation difference is only about 200 m. I conclude that the authors believe that this map is correct. Hence, I get the impression that the authors do not realize the realism of the topography of the studied river basin, and they approached the analysis very formally. Moreover, what kind of arable land can there be on slopes close to 90 degrees? Is this extreme terraced farming? But there is no information about this in the text of the manuscript. Moreover, analysis of the erosion under terraced agriculture requires another approach.

Given the unrealistic nature of such a distribution of slopes in a plain river basin, I am distrustful of all the other findings based on the data from the map (5a). I do NOT recommend this manuscript in its current form for publication.

Author Response

We would like to thank the reviewer for the thorough review of our manuscript, the encouraging words, the helpful comments, and the opportunity to resubmit the revised copy of our manuscript: ID: water-1423699. We have addressed all comments as suggested by the reviewer in our manuscript. As indicated below.

Point 1: In the revised version of the manuscript, I have not found any changes to the map in Figure 5a. Slopes close to 90 degrees still dominate there almost everywhere. This is extremely strange for a large river basin (about 42 thousand square kilometers), where the elevation difference is only about 200 m. I conclude that the authors believe that this map is correct. Hence, I get the impression that the authors do not realize the realism of the topography of the studied river basin, and they approached the analysis very formally. Moreover, what kind of arable land can there be on slopes close to 90 degrees? Is this extreme terraced farming? But there is no information about this in the text of the manuscript. Moreover, analysis of the erosion under terraced agriculture requires another approach.

Response 1: Thank you so much for your comments. Yes, you’re right. I rechecked the manuscript and just found a mistake in Figure 5a legend, which is more unrealistic. Now, this mistake has been rectified and has been replaced with a new figure legend in Degree with a better understanding. Slope maps highlight the regions with high potential runoff and then high erosion rate; these potentials are decreases from high slope degree to lower slope degree. Hopefully, you will find it justified.

 

Author Response File: Author Response.pdf

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

Round 1

Reviewer 1 Report

This is a numerical exercise of soil erosion estimation. The proposed scheme of the combination of the model and GIS information is powerful. However, the estimated result depends on the applied formula, and there are no discussion the validation of the results.

For example, the background on the numbers in equation 2 is not well explained. How the value of the coefficient 0.0483 and 1.61 were obtained. I mean, what is the evidence of these value, and the conditions of the values in other parameters K, LS, C, P. 

Also, the references for the numbers in table 2, and table 3 is necessary.

At least, the discussion on the procedure/scheme for the validation is necessary.

Note, I suppose the Figure 3 and Table 4 shown in line 266-267 are missing.

In addition, for equation (3), how the value of FA are obtained?

The results of R is shown in Fig.4. However, the rainfall is not uniform, but the calculated value of R is very smooth. Why?

In general, the colored results is not easy to understand the details. The definition of "slope value" in Fig6(a) is unclear. Figure 8 should be plotted by contour lines, otherwise the readers cannot understand the distribution.

To obtain the conclusion as "the current research has demonstrated the effect of human induced...", some comparison of output with/without human activity is necessary. Also, I think some level of sensitivity analysis may be necessary.

Reviewer 2 Report

You will find any further remarks in the attached pdf.

The work is described superficially, e.g. for methods: DEM 30 seconds ... instead of -Global 30 Arc-Second Elevation (GTOPO30) -; Word instead of World (176), TRMM only gives precipitation amounts in mm instead of mm / h (178) and gives no new information.

The number of decimal places should be implemented according to the statement. Precipitation (142) 70.07 is statistics, one decimal number is enough; while soil erosion with the gram specification is nonsense (Table 4).  The used R, K and C factors as well as P are chosen very simply. The LS factor is also calculated too roughly in relation to the scale (fig 6 slope in ° or %?). The conclusions are quite simple. They have been described repeatedly around the world (Borrelli, P. et al. 2021: Soil erosion modeling: a global review and statistical analysis. Science of the Total Environment 780, Article 146494.).

Your work contains too little scientific substance and your own contributions to further development and also references to the protection of the soil and the environment in Niger are missing. 

Comments for author File: Comments.pdf

Reviewer 3 Report

Dear Authors,

I always support the creation of a new soil erosion map, I also do it this time.

The title is almost OK and reflecting the content, however, I suggest removing the word "risk" as what you present is not a risk assessment, it is the assessment of the "present" situation.

On the one hand.

On the other hand, the specific aims are promising much more than what we get from the manuscript:

"The specific aims are to: a) create a method that integrate remote sensing data and GIS with the RUSLE to estimate the spatial distribution of soil loss erosion at the overall study area, b) examine the impact of land use/land cover changes on erosion using remote sensing and GIS, and c) generate a soil risks erosion map in the study area using the overlay approach. "

I would say that aim a) is fine and authors managed to reach it.

Aim b) is not even mentioned in the manuscript and I do not see any effort to get closer to this aim, there is no time series of and use, nor C factors from different years that would give a chance to reach this specific aim.

Aim c) is the same, as I mentioned it in relation with the title. The risk assessment would be the use of the RUSLE model e.g. with the worst C factor of plants on the arable field, and/or running the model with the highest R factor, etc. But it is not there! 

So, I would say that the specific aims were not really reached.

For this very reason, I would say that a "simple" model running is not really reaching the level of novelty. 

If there were real risk analyses, especially with the inclusion of the land-use change that would have added "enough" novelty for the manuscript to be publishable. 

Furthermore, I have to say that I was very happy that the dimensions were in adequate magnitude (normally authors do not know the limits), until I could that the acres in the abstract became tons in the manuscript. This MUST BE sorted out, it is not a proper representation this way.

Furthermore, I have some other concerns related to parametrization of the model:

1. R factor: what is the resolution of the rainfall data? Do you have any rainfall measuring device on the area at all?
2. K factor map: what is the resolution of the Digital soil map of the World?
3. K factor: one soil normally has one K factor, providing categories is pointless. Also keep in mind that it is not possible to reach the 0 value! So, the range of the K factor cannot start at 0!!!!
4. C values: vegetation is not a proper category. You can say that it is “Other” vegetation but then you need to explain it!
5. C factor: Similarly to the K factor, one land cover normally has one C factor, so you have to decide if your grassland has 0.19, 0.23 or anything in between, otherwise you need to explain, why one grassland has a lower and the other one a higher value. It is similar in all classes! On the other hand, vegetation cannot have 0.00 value because it means that there was no erosion at all, 0.01 is small enough already. Why do you use categories instead of decent values? It is OK but explanation is needed, I mean you NEED to give the exact name of a certain land cover or crop and its value, otherwise the category is useless!
6. C factor: similarly to the K factor, keep in mind here as well that it is not possible to reach the 0 value! So, the range of the C factor cannot start at 0!!!!
7. C factors: what was the resolution of your land use map?
8. P factor: what is the source of the P factor map? How do you know that the whole area has 0.5 value???
9. What is the range of the spatial resolution of your input maps and what do you consider as a final resolution of your result map?

I saw that the manuscript is considered as a review. I think that the elaboration of the parameters of the RUSLE model is not good enough for a review, and the article looks like a "normal" article as there is a model running with the results of the modeling.

So I have to say that I need to reject the article in the present form.

I encourage the resubmission, especially if the risk assessment and the land-use change can be incorporated.

Best regards, Reviewer X

PS: see some other comments in the pdf file.

 

Reviewer 4 Report

Dear Editor.

I have finished my review on the proposed paper “Soil erosion risk assessment using the RUSLE model and Geospatial techniques (Remote Sensing and GIS) in South-Central Niger (Maradi region)” water-1346242-peer-review-v1.

 

Summary of the manuscript:

In the proposed paper, the authors’ goal is to estimate the annual soil erosion using the RUSLE model. The research is a case study that was held at the South-Central Niger (Maradi region), Africa. The research is a combined methodology of known model RUSLE and application of satellite data and GIS techniques.

 

General review:

The proposed paper is well structured. It begins with the Introduction and provides the appropriate references that help the reader to get into the subject immediately. In Introduction there is an effort to provide previous studies with similar scientific content. However, the authors do not provide much literature from other studies that were conducted in other countries. Authors describe and set the scientific problem and how other researchers have approached. At the end of Introduction, authors state the goals of the research. The methodology is generally interesting and well explained, so other researches could easily repeat this research methodology. Although, the methodology is interesting, however it is not novel, as it incorporates and combine already known models and applications. The results are very well stated and in my opinion tables and figures are easily understandable, However, I think that some minor changes should be made. The results scientifically explained, but without the appropriate use of literature and comparisons with other similar studies. The quality of the work in Results and Discussion are appropriate for this paper.

 

Points for revision:

I have some points for revision.

Line 41: Make capital the first letter of the “furthermore”.

Lines 168-177: remove the URLs. Add literature and move the URLs at the reference section.

Figure 2: Please, enlarge figure 2. There is enough space.

Table 1: Remove the URLs from the table. In the table at 3^rd column you will add the name of the service that provide the data. And at the reference list you will add the URLs.

Line 248: Here, you refer first time the table 3. But the table 3 is in the next page. I propose change the placement of table 3, close to the first reference.

Line 268: The same with the above comment. Her you refer first time the table 4. But the reader will find this table after 5 pages!!!

Figure 3: This is a map of LULC. And is locate at methodology section. However, the other maps are locate in results. This figure is not a result?

Generally, rearrange figures and tables to be close to the first mention in the text, and to be is the same section.

Table 3 and elsewhere in the text: What you saying “vegetation”??? What kind of plants leave in “vegetation”? Trees, grass…?

Lines 349-351 and figure 8: You say that the P-factor is different between south and “upper and outer parts” of the study area. First, what you mean with “upper and outer”??? North? Northeast….? And second, from figure 8 it is not possible to see the differences of P-factor between south and upper parts that you say in the text. I see only one color that belongs to 0.5 P-factor.

Line 370: “While the technique has some limitations,….”. Which are these limitation??? This is very interesting. Discuss the limitations.

Figure 9: the areas with high erosion rates are not very easy to be seen in the figure 9, because they are very small. I propose to add a table with the 5 categories from the figure 9, and add a column with the area that cover these categories.

Validation: Generally, there is no validation of your results, and this fact reduces the worth and reliability of your research. I understand that this area is ungauged. However, a solution to solve this problem is to find other researches from areas with similar characteristics and compare your results.

 

Some discussion to enrich your Introduction.

Lines 56-64: Soil erosion is a very significant problem for sedimentation of natural lakes and manmade reservoirs. The lifespan of reservoirs directly affected by annual soil erosion rates. You did not refer anything about this problem. I propose to add here a sentence about this problem with the appropriate literature. I propose 3 papers to add, but you can add more (Kastridis and Kamperidou 2015, Maina et al. 2019, Iradukunda and Bwambale 2021).

Lines 107-108: You refer in the text “GIS and remote sensing allow the use of spatial data of different types”. I propose to extent this sentence and say that GIS and remote sensing are widely applied in many research areas and mainly in flood risk assessment that is directly associated  with soil erosion, as extreme hydrological events generate soil erosion and sediment transport. I propose 2 papers with floods and GIS-remote sensing but you can more to enrich your paper (Tzioutzios and Kastridis 2020, Pangali Sharma et al. 2021).

 

References

 

Parfait Iradukunda & Erion Bwambale (2021) Reservoir sedimentation and its effect on storage capacity – A case study of Murera reservoir, Kenya, Cogent Engineering, 8:1, DOI: 10.1080/23311916.2021.1917329

Kastridis A., Kamperidou V. (2015): Influence of land use changes on alluviation of Volvi Lake wetland (North Greece). Soil & Water Res., 10: 121-129.

Maina, C. W., Sang, J. K., Raude, J. M., Mutua, B. M., & Moriasi, D. N. (2019). Sediment distribution and accumulation in Lake Naivasha, Kenya over the past 50 years. Lakes & Reservoirs: Research & Management, 24(2), 162–172. https://doi.org/10.1111/lre.12272

Pangali Sharma, T.P.; Zhang, J.; Khanal, N.R.; Prodhan, F.A.; Nanzad, L.; Zhang, D.; Nepal, P. A Geomorphic Approach for Identifying Flash Flood Potential Areas in the East Rapti River Basin of Nepal. ISPRS Int. J. Geo-Inf. 2021, 10, 247. https://doi.org/10.3390/ijgi10040247.

Tzioutzios, C.; Kastridis, A. Multi-Criteria Evaluation (MCE) Method for the Management of Woodland Plantations in Floodplain Areas. ISPRS Int. J. Geo-Inf. 2020, 9, 725. https://doi.org/10.3390/ijgi9120725.