An Enhanced Flume Testing Procedure for the Study of Rill Erosion

Round 1

Reviewer 1 Report

Paper presents the development and verification of a flume apparatus and corresponding testing methodology. The title of the paper talks about "cost-effective" procedure, from which I got the impression that the paper talks about the improvement of the well-known procedure from economic point of view. However, after reading the article, it turned out that this is de facto testing on an affordable simple apparatus. For this reason, I suggest to modify the title of the paper.

Description of the procedures / methods is very brief in some parts, which is sometimes at the expense of clarity.

In the Discussion section, I recommend discussing and confronting more the own results with the results of other authors.

Discussion about Fig. 4a is missing.

Line 219 : what kind of unit is mL.s^-1 ? is it correct regarding to previous text?

Lines 249-251 : in these lines the authors state the units of variables in a different format than in the rest of the text - it is necessary to unify

Fig.3 : it is not clear the meaning of marks in the figures… what is the difference between full and empty marks? What they represent? It is necessary to put description in the legend of the figure or in the name.

Fig.5: what is the difference between 5a and 5b or between 5c and 5d – conditions are the same!.... check the text under the figure

Author Response

REVIEWER #1

Before answering the specific comments from Reviewer 1, we would like to thank him for his detailed review of our manuscript and for his constructive and useful remarks. We have tried to address each comment accordingly. We would also like to inform that the manuscript went through an additional round of detailed revisions. Some typos have been corrected and a few sentences have been improved. All modifications were clearly marked using the “track changes” tool in Microsoft Word.

COMMENT: Paper presents the development and verification of a flume apparatus and corresponding testing methodology. The title of the paper talks about "cost-effective" procedure, from which I got the impression that the paper talks about the improvement of the well-known procedure from economic point of view. However, after reading the article, it turned out that this is de facto testing on an affordable simple apparatus. For this reason, I suggest to modify the title of the paper.

RESPONSE: We have modified the title according to your suggestion and removed the term “cost-effective”.

COMMENT: Description of the procedures / methods is very brief in some parts, which is sometimes at the expense of clarity.

RESPONSE: Thank you for your comments, which prompted the authors to review the Materials and Methods section. We have made a sincere attempt to improve that section and included additional information at several specific points. We hope that the newly included information coincides with the manuscript portions that the Reviewer considered lacking.

- Section 2.1. The authors believe that Section 2.1 was fairly detailed in the original manuscript version. However, a brief description of “uniform flow” conditions was added.

- Section 2.2. Several improvements were included. The authors believe that the paragraph detailing the specimen compaction procedure could be considered slightly confusing, particularly with respect to the scraping of excess material and the reasoning behind this step. That paragraph was modified to also improve readability.

- Section 2.3. The procedure for swapping the eroded mass sieves was described in greater detail.

- Section 2.4. Text was revised to improve readability.

COMMENT: In the Discussion section, I recommend discussing and confronting more the own results with the results of other authors.

RESPONSE: We agree with the Reviewer’s remarks. We have revised the Discussion section and included important references that are relevant to the manuscript.

COMMENT: Discussion about Fig. 4a is missing.

RESPONSE: We have modified the text to indicate more clearly when we were referring to Figure 4a.

COMMENT: Line 219 : what kind of unit is mL.s-1 ? is it correct regarding to previous text?

RESPONSE: Thank you for pointing that mistake out, we have corrected the units.

COMMENT: Lines 249-251 : in these lines the authors state the units of variables in a different format than in the rest of the text - it is necessary to unify

RESPONSE: We have complied with the Reviewer’s suggestion and unified the units.

COMMENT: Fig.3 : it is not clear the meaning of marks in the figures… what is the difference between full and empty marks? What they represent? It is necessary to put description in the legend of the figure or in the name.

RESPONSE: We have included the following sentence to the figure title: “Filled and empty markers of the same shape indicate two test pairs that were carried out under identical conditions.” We believe that this modification addresses the reviewer’s concerns. 

COMMENT: Fig.5: what is the difference between 5a and 5b or between 5c and 5d – conditions are the same!.... check the text under the figure

RESPONSE:  Thank you for point that out. We have modified the figure title as follows: “Figure 5. Specimen surface condition after flume tests for various void ratios and hydraulic shear stresses: a) test #5, at e = 1.0 and τ_h = 1.93 Pa; b) test #6, at e = 1.0 and τ_h = 1.93 Pa; c) test #7, at e = 1.5 and τ_h = 0.82 Pa; and d) test #8, at e = 1.5 and τ_h = 0.82 Pa.”

Reviewer 2 Report

A BRIEF SUMMARY

The paper titled “An Enhanced Cost-Effective Flume Testing Procedure for the Study of Rill Erosion”, presents an interesting topic for readers of this Journal.

However, some open questions remain after reading the paper. Below is the list of some questions that need to be addressed for the next submission.

• Probably a more accurate references research could help to add value for this topic. I strongly suggest that the authors try to add some more references especially in the "part 1 (introduction)" of the paper. For example there are the following recent papers on this topic:

doi:10.3390/su13116058

doi: 10.3390/su13041991

doi: 10.1016/j.iswcr.2015.10.001

• In your opinion, can you improve this study with a continuous hydrological modeling? I suggest to read https://doi.org/10.1016/j.jhydrol.2020.125664.
• I am having serious difficulties in understanding the article, because in several lines there is an error that does not allow to read reference. See specific comments, please.
• Please, more comments for Formula n.4. I don’t understand like you have obtained it.
• In conclusion, the authors have to specify the novelty of the proposed approach and the future improvements. You have to replace conclusions; this paragraph now seems an extended abstract.
• Finally, I suggest to go ahead in this very interesting research. Boa sorte!

SPECIFIC COMMENTS

Keywords: I suggest to replace “erosion” with “soil erosion” and to add “experimental tests” (core of your paper!)

I would like to read again your paper, without these errors:

Line 42: “Error! Reference source not found”

Line 48: “Error! Reference source not found”

Line 54: “Error! Reference source not found”

Line 101: “Error! Reference source not found”

Line 164: “Error! Reference source not found”

Line 231: “Error! Reference source not found”

Line 271: “Error! Reference source not found”

Line 282: “Error! Reference source not found”

Author Response

REVIEWER #2

COMMENT: The paper titled “An Enhanced Cost-Effective Flume Testing Procedure for the Study of Rill Erosion”, presents an interesting topic for readers of this Journal. However, some open questions remain after reading the paper. Below is the list of some questions that need to be addressed for the next submission.

RESPONSE: We would like to thank Reviewer #2 for his detailed review of our manuscript. The paper was carefully revised according to the offered remarks. We would also like to inform that the manuscript went through an additional round of editorial revisions and some typos have been corrected. Some sentences have been improved. All modifications were clearly marked using the “track changes” tool in Microsoft Word.

COMMENT: Probably a more accurate references research could help to add value for this topic. I strongly suggest that the authors try to add some more references especially in the "part 1 (introduction)" of the paper. For example there are the following recent papers on this topic:

doi:10.3390/su13116058

doi: 10.3390/su13041991

doi: 10.1016/j.iswcr.2015.10.001

RESPONSE: We believe that the original manuscript offered as fairly extensive literature review, focused on the issues directly related to laboratory flume testing. However, the original literature review did not make any reference to studies that employed field-testing and field monitoring techniques. For this reason, we agree with the reviewer’s remarks and have included a few additional sentences that deal with field-testing, including the suggested references.

We would like to note that we believe that a discussion regarding field-testing alternatives is particularly useful for the conclusions section, because it offers an opportunity for comments on the limitations of the proposed apparatus and testing approach. Therefore, we decided to add these comments and references to the conclusions section.

COMMENT: In your opinion, can you improve this study with a continuous hydrological modeling? I suggest to read https://doi.org/10.1016/j.jhydrol.2020.125664.

RESPONSE: Thank you for the suggested read. The paper by Grimaldi et al. is interesting and relevant to the general area of soil erosion modeling. Our study is specifically focused on establishing adequate techniques for evaluation of soil erodibility parameters. In this sense, the establishment of representative field hydraulic conditions is of paramount importance. The hydraulic shear stresses and corresponding flow velocities selected for soil testing must, ideally, be based on expected field values. To answer your question directly, yes, any hydrologic model that offers improvements to the quantification of field hydraulic conditions is useful for the adequate design and planning of experiments. We would like to inform Reviewer #2 that we took this opportunity to cite this paper in the conclusions section.

COMMENT: I am having serious difficulties in understanding the article, because in several lines there is an error that does not allow to read reference. See specific comments, please.

RESPONSE: We would like to apologize for the “Reference source not found” instances. We have removed all cross-references to make sure this problem will not occur again.

COMMENT: Please, more comments for Formula n.4. I don’t understand like you have obtained it.

RESPONSE: Equation 4 refers to Newton’s method (also known as Newton-Raphson’s method), which is widely used for the solution of nonlinear systems. We have included more clear definitions of the equation’s variables, in an attempt to address the Reviewer’s concerns regarding any possible lack of clarity.

COMMENT: In conclusion, the authors have to specify the novelty of the proposed approach and the future improvements. You have to replace conclusions; this paragraph now seems an extended abstract.

Finally, I suggest to go ahead in this very interesting research. Boa sorte!

RESPONSE: We have improved the conclusion section according to the Reviewer’s remarks.

SPECIFIC COMMENTS

COMMENT: Keywords: I suggest to replace “erosion” with “soil erosion” and to add “experimental tests” (core of your paper!)

RESPONSE: Thank you for the remark. We have made the suggested modifications.

COMMENT: I would like to read again your paper, without these errors:

RESPONSE: Again, we sincerely apologise for the formatting error.

COMMENT:

Line 42: “Error! Reference source not found”

Line 48: “Error! Reference source not found”

Line 54: “Error! Reference source not found”

Line 101: “Error! Reference source not found”

Line 164: “Error! Reference source not found”

Line 231: “Error! Reference source not found”

Line 271: “Error! Reference source not found”

Line 282: “Error! Reference source not found”

RESPONSE: All cross-references have been removed.

Reviewer 3 Report

Dear Authors,

I really liked your manuscript. It is a spot on simple but very practical report others likely would use your methods proposed. I think the manuscript needs only minor revision and that is mostly on some technical issues. By some reason there are some mess up with your referencing and that needs to be checked/updated. Similarly some symbols in the equations and within the main text displayed differently as you might have intended to do it. I think the science and structure, the method presentation and the results you provide are fine. Maybe in the discussion, or in the sections after the main result presentation some line would fit well about the applicability of the method in other regions, something like listing the benefits and maybe the potential issues where the method wouldn't work well.

Minor revision is suggested

Kind regards

Author Response

REVIEWER #3

COMMENT:  Dear Authors,

I really liked your manuscript. It is a spot on simple but very practical report others likely would use your methods proposed. I think the manuscript needs only minor revision and that is mostly on some technical issues. By some reason there are some mess up with your referencing and that needs to be checked/updated. Similarly some symbols in the equations and within the main text displayed differently as you might have intended to do it. I think the science and structure, the method presentation and the results you provide are fine. Maybe in the discussion, or in the sections after the main result presentation some line would fit well about the applicability of the method in other regions, something like listing the benefits and maybe the potential issues where the method wouldn't work well.

Minor revision is suggested

Kind regards

RESPONSE: We would like to thank Reviewer #3 for his useful remarks. We have tried to address each comment accordingly. All modifications were marked using the “track changes” tool in Microsoft Word.

- We have checked all references.

- Typos have been corrected and a few sentences have been improved.

- We have revised all equations and equation symbols used along the main body of the manuscript.

- We have improved the discussion and conclusion sections.

Round 2

Reviewer 1 Report

I thank the authors for their efforts to improve the manuscript. Despite all efforts, however, the comparison of the achieved results with the information published in the literature was not completely fulfilled. In the future, I recommend to discuss and try to compare the own achieved values ​​ with  ones obtained by others authors in similar or different conditions or mention why the own achieved result cannot be compared with others.

Author Response

We would like to thank Reviewer 1 for his constructive criticism. We realize that it would be beneficial to include more comparisons to previous studies or to clearly state areas were the literature lacks results. We have tried to address this last remark. However, we must also recognize that there is limited data in the literature using open channel/fixed specimen flumes.

The following improvements were done to Section 3, Results and discussions:

1) The first paragraph was rewritten to improve clarity. We believe that the methodology for evaluating test results is one of the main highlights of the manuscript. This paragraph does not present comparisons of result to literature data per se. Nevertheless, it offers an important contrast between the methodology presented in the manuscript and the methodology employed in previous studies.

2) 6th paragraph, immediately after Table 1. The following sentence was included:

“Unfortunately, previous studies using open channels and fixed specimens have not presented similar systematic evaluations of repeatability whose results could be compared to those presented herein.”

3) Last paragraph of Section 3. The following new paragraph was included:

“The lateritic soil studied herein presented a τ_c of 0.69 to 0.78 Pa and a K_r of 0.0014 to 0.012 g cm-2 min-1 Pa-1. The values of τ_c and K_r of lateritic soils vary greatly and depend on the soil texture, soil weathering, and stability of particle aggregations. Some values of τ_c reported in the literature for lateritic soils range between 0.01 and 1.33 Pa [15, 49, 50]. The range of K_r for lateritic soils reported by the same authors varies between 0.01 and 36.5 g cm-2 min-1 Pa-1 [15, 49, 50]. Therefore, the results presented in Figure 4 fall within these typical ranges, but also indicate that the soil studied herein has a relatively low erodibility, when considering the values for other lateritic soils.”

Reviewer 2 Report

Congratulations. The paper has been improved. In my opinion it is worthy of publication in present form.

Author Response

We would like to once again thank Reviewer #2 for his useful remarks that prompted us to further improve the manuscript.