Advanced Numerical Modeling of Sediment Transport in Gravel-Bed Rivers
Round 1
Reviewer 1 Report
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Comments for author File: 
Comments.docx
Author Response
Dear Reviewer 1,
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Authors
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Reviewer 2 Report
I have read the interesting work "Advanced numerical modeling of sediment transport in gravel-bed rivers" from Bui et al.
The manuscript is clear and flows, presenting properly the steps for computing the proposed numerical model, and the results obtained in applying the model to the three cases.
I have some suggestions that may require minor changes.
1) please, check carefully the citations of Figures in the texts (numbers and letters). Some numbers and/or letter are missing, or may be wrong...especially in Results and Discussion. Check also Table numbers (there are two Table 1).
2) personally, I prefer to read the Discussion in a separate section from Results. Since you presented three different applications (one numerical and 2 physical models), and numerous comparisons with other models, a singular Discussion section would help the reader in evaluating the perfomances.
3) In Figure8-11, Fig. 13, the title would help. As you did in Figure 6 and 7
4) please, specify the errors computed in Table 2 caption (it will be Table 3) (R?)
Author Response
Dear Reviewer 2,
please find attached the responses.
Thanks and regards.
Authors
Author Response File: Author Response.docx
Reviewer 3 Report
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Comments for author File: 
Comments.pdf
Author Response
Dear Reviewer 3,
Please find attached the responses.
Thanks and regards.
Authors
Author Response File: Author Response.docx
Reviewer 4 Report
General comments to the authors
In the present paper a new sediment transport numerical model is presented, which deals with gravel-bed rivers, considering porosity variability and fine sediment fluxes between different bed layers.
The paper is generally well organized and clearly written.
However, I have some concerns, mainly related to the numerical model, which must be resolved, before the paper can be published.
I have found some typos, though there may be others. So, I suggest the paper be double checked by a professional English writer.
Detailed comments
At line 86, the authors state that they “only consider bed load” and this is in contrast with lines 94-95, where then they write that “sediments in this layer can be transported as bed load, suspended load, or infiltration”. This must be fixed.
Lines 91-92. The “multi-layer concept” could be better introduced.
Line 93. “several substrate layers”: this is misleading, because in the following only 2 layer are considered.
Lines 95-96. For greater clarity, it would be better to add something like “as it will be discussed below”.
Line 97. With “top substrate” do the authors mean layer (2) in Figure 2? This should be added.
Line 97. If I understand well, the author state that fine particles could be removed by the flow as suspended load. Is this correct? If so, how is this possible, neglecting suspended load?
Lines 109-111. The sentence “The horizontal exchange …” has already been stated at lines 106-107.
Line 113. How is qb evaluated?
Line 116. What is qb,j? I guess, the bed load discharge of sediment size-class j. Is this correct?
Line 118. Here the authors apply both theorem of mean values and Leibniz integral rule. Isn’t it? This must be specified.
Lines 134-135. I guess, something is missing in this sentence.
Equation (7). Should it be betas,j instead of betab,j (with refer to active stratum layer)? And should it be qbj instead of qb (with refer to sediment discharge of size class j)?
Lines 175-177.The symbols of vectors should be the same in the equations and in the text. This must be fixed.
Lines 195-196. From this sentence I understand that the infiltration between active layer and active stratum layer is evaluated through the DEM model, solving equations (8) and (9). Is this correct? What about equation (7)? It is not very clear how the infiltration is evaluated. I see two different approaches; the former is based on equations (3), (5), (6) and (7); the latter on the DEM model. Which one has been followed? This is a key point in the present paper and it needs to be better clarified.
Moreover, I see no references to the flow in the equations. How is it evaluated? And how does it influence the sediment balance equations?
In all the tests, the number of particles used should be declared. Moreover, a discussion needs to be made (here or in the Introduction/Conclusions) if this kind of model is applicable to wide domains as for example those reported in the suggested references.
Section 3.2. It seems that something is missing: the authors talk of a dune, which has not been introduced before. It seems that all the experiment has not been described (dune, water flow, sediment discharge evaluation, etc.). This must be fixed.
Lines 343-344. Can the author provide a comparison also with observed data?
Lines 370-371. Please, move these lines in the table caption. The same applies to lines 436-437.
Suggested references.
Chiu Y.-C., Lee H.-Y., Wang T.-L., Yu J., Lin Y.T. and Yuan Y. (2019). Modeling Sediment Yields and Stream Stability Due to Sediment-Related Disaster in Shihmen Reservoir Watershed in Taiwan. Water 2019, 11(2), 332
Petti M., Bosa S and Pascolo S. (2018). Lagoon Sediment Dynamics: A Coupled Model to Study a Medium-Term Silting of Tidal Channels. Water 2018, 10(5), 569
Török G.T., János Józsa J. and Baranya S. (2019). A Shear Reynolds Number-Based Classification Method of the Nonuniform Bed Load Transport. Water 2019, 11(1), 73
Author Response
Dear Reviewer 4,
Please find attached the responses.
Thanks and regards.
Authors
Author Response File: Author Response.docx
Round 2
Reviewer 4 Report
I appreciate the time the authors have spent to prepare the revised version of their paper. They have very thoroughly addressed all my comments, then in my opinion the paper can be accepted in present form.
