Analysis of Bed Sorting Methods for One Dimensional Sediment Transport Model
Round 1
Reviewer 1 Report
The manuscript deals with the applicability of the bed sorting method (i.e., active layer method), which is available in HEC-RAS, for sediment transport modeling. The model was validated with historic data from the Geum River, Korea.
The article is an original contribution and the topic is of interest for the readership of the Sustainability journal. The analysis of a case study strengthens the research.
English language is clear, the presentation is satisfactory; anyway, I have detected some criticisms in the text that should be properly addressed. Authors should add more information on model creation, and model data/field data. Some results should be further commented.
The Authors can benefit from the comments below to improve their paper. These have to be accomplished before manuscript acceptance.
Title
Title is appropriate.
Abstract
The abstract is concise and reflects the content of the article. I recommend avoiding symbols in the abstract since they are defined later in the text.
Keywords: ok.
Introduction
Aims of the study are properly clarified in the Introduction. Relevant references are included.
Lines 85-87: It should be specified that open-source software HEC-RAS is widely adopted for the hydraulic simulation of river floods and for the numerical investigation of the effect of structures that affect the river cross section. In this regard, Authors are recommended to include, among others, the following references in order to enhance the introductory discussion:
- Cappato A., Baker E.A., Reali A. Todeschini S., Manenti S. (2022). The role of modeling scheme and input uncertainty in the analysis and mitigation of backwater induced urban flood-risk, Journal of Hydrology, 614 (128545), https://doi.org/10.1016/j.jhydrol.2022.128545.
- Ardiclioglu M., Mohamed Hadi A.M.W., Periku E., Kuriqi A. 2022. Experimental and numerical investigation of bridge configuration effect on hydraulic regime. Int. J. Civ. Eng. https://doi.org/10.1007/s40999-022-00715-2 (0123456789).
This introductory discussion would further enforce the suitability of the adopted software.
Methodology
This section is clear, and adequately detailed. Relevant references are included. The provided figures are clear and effective for the presentation of the methodology.
Line 173: please define d90.
Model set up
This section quite clear, but some more information and improvement are required
The provided figures and table are clear and necessary for the presentation.
Line 196: Please specify how the adopted cross sections have been acquired.
Lines 207-208: “The channel geometry data and roughness coefficient from MOLIT (2016) were applied [20].” Even if proper references are cited, Authors are recommended to discuss the relevant aspects related to model creation and calibration.
Lines 211-212: Authors should specify how interpolation was carried out.
Line 221: Figure 5 shows a model underestimation in stations 1 and 3, while a model overestimation in station 2. Authors should comment/discuss on this result.
Evaluation of Bed Sorting Methods
This section is clear and presented in a logical sequence. The provided figures and tables are useful for the presentation of the results.
Line 279: “there are quite number of points exist on 3rd quadrant …”. Please, check the text.
Lines 292-293: “bed material size of active layer method has stable”. Please, replace “has stable” with “is stable”.
Summary and conclusion
Conclusions seem reasonable and are supported by the results.
Lines 321-322: Authors should discuss on possible approach, other than increased data availability, to improve the results returned by three layers methods.
References
Several relevant references are cited in the text. Two references are recommended addressing/strengthening the choice of HEC-RAS software. Apart from these reference, based on my knowledge, no important reference is missing.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
- Sediment transport is not the same as the process of bed scouring. In general, it can be said that fluvial processes are crucial for river morphology, while among these processes we can distinguish erosion (in its various forms), sediment transport and accumulation.
- The issue of debris transport and its modeling is very poorly described. Very few sources are cited, and yet, even limiting ourselves to just the debris transport formulas implemented in HEC-RAS, there are many sources in the literature
- Line 90: "However, it is very difficult to figure out a solution of sediment transport, because the relationship between sediment and hydraulic properties is very complicated" - a rather succinct statement. The thread needs to be developed, and elements of stream velocity distribution, turbulence, pulsation velocities should be woven into the description.
- I have done such laboratory experiments many times, wanting to capture the moment of the sorting and armoring process, but I have never been able to take a photo or video of the expressed mixing of the material. Did the authors make such an attempt? Driven by research curiosity, I submit such a topic for consideration and invite you to contact me
In my opinion, the article has interesting results, but it definitely needs a better introduction and a broader literature review in terms of the Sorting & Armoring process itself. Ask yourself: what does the intensity of these processes depend on?
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
General comments:
The manuscript, entitled "Analysis of Bed Sorting Methods for One Dimensional Sediment Transport Model", is an interesting study to investigate the application of the two bed sorting methods. It touches on an important topic. There are some problems, which need to be solved before it is considered for publication.
Specific Comments:
1. This manuscript selects the Geum River as the study area to investigate the application of the two bed sorting methods. However, the conclusion that active layer method has greater applicability appears to be unconvincing using only one river and lacking of mechanism analysis.
2. Line 219, three stations were used to valid model performance, while their locations were not marked in the Figure 3.
3. Line 241, Table 2 shows that authors choose the Engelund-Hansen and Laursen equations to calculate sediment transport. Do different sediment transport equations or their combination with bed sorting methods have significant effects on results?
4. Line 258, what does the variable d50 mean? Why choose d50 as an evaluation indicator to analyze the applicability of the bed sorting method?
5. In ‘4. Evaluation of Bed Sorting Methods’, this section has evaluated the applicability of the bed sorting methods, but I didn’t see much discussion of the results. It needs to be added appropriately to improve reliability of the results.
6. Figure 8 shows temporal sediment size variation. Why d50 decreases between about 200~340 hours in Figure 8(a) and between about 100~140 hours in Figure 8(b)? Does the phenomenon affect the relationship between bed elevation and bed material size changes (Figure 7) if we define d50,f as d50 after 200 hours or 100 hours?
7. Line 196, the locations of 106 cross sections should be supplemented for better understandings of the model setup.
8. Figure 8 shows the results of a cross section at 125.66 km from the downstream boundary. Which quadrant does this cross section locate in? How does the temporal sediment size of cross sections in other quadrants vary?
9. Line 282, authors should discuss the reasons that the Copeland method combined with Engelund-Hansen equation and the Thomas method respectively performs differently. In addition, the characteristics of cross sections located in 3rd quadrant should be summarized to reveal sufficient conditions to apply the active layer method or the three layers methods.
Author Response
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Author Response File: Author Response.pdf
Reviewer 4 Report
The authors have set up a chapter Model Setup which talks partly about the material of the work. It is necessary to reinforce a little about the material itself and some physical-geographical characteristics of the watershed itself, which are geology, pedology, and land use/land cover. I suggest that the material and method be combined and that the model setup be a chapter by itself.
Line 194, I think it's better to start the sentence with text and not with numbers
The title of picture number 5 should be on the same page as the picture itself
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The manuscript has been significantly improved following the recommendations of the Reviewers; all my concerns have been addressed and convincingly justified.
Author Response
Thank you very much for your comments. Your comments significantly contributed to the upgrade of the quality.
Reviewer 2 Report
Thank you for the authors' comprehensive responses. As it stands, I recommend the article for publication, while inviting your cooperation.
Author Response
The recommendations were really helpful to improve the quality of the paper. We are looking forward to cooperating each other.
Reviewer 3 Report
Thanks for the revision of the manuscript. I read the author's revisions and responses carefully. There are some problems, which need to be solved before it could be considered for publication.
1. Line 309~310, it is not realistic that bed material gets finer when scouring. Whether it can be inferred that it is also unrealistic that bed material gets coarser when depositing? Therefore, are the cross sections located in the 1st quadrant also the indictor the poor capability of simulating armoring process?
2. Line 318~322, the characteristics of cross sections located in 3nd quadrant have been summarized, while impacts of these characteristics on simulating armoring process were not revealed.
3. Line 221~226, some cross sections are hydraulic structures and confluence. Do hydraulic structures or confluence affect the temporal sediment size variations of cross sections?
4. Line 353~356, bed materials on the depositional cross sections are directly affected by the characteristics of incoming sediment from the upstream. Does it mean that both the active layer method and the three layers methods are difficult to accurately simulate temporal sediment size variation? It is recommended to give the temporal sediment size variation at representative cross section located in 1st or 4th quadrant if possible.
5. The formatting need further revision. It is recommended that the significant digits after the decimal point are consistent in Table 4.
Author Response
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Author Response File: Author Response.pdf
