Improved Coastal Erosion Prevention Using a Hybrid Method with an Artificial Coral Reef: Large-Scale 3D Hydraulic Experiment

Round 1

Reviewer 1 Report

The paper „Improved coastal erosion prevention using a hybrid method with an artificial coral reef: Large-scale 3D hydraulic experiment” by Kim et al. presents interesting hydraulic model tests on a topical issue in coastal protection. The overall structure and content of the paper give a good insight into the study. The model setup and results are well illustrated with figures, diagrams and tables.

A few issues should be considered in the revision of the manuscript:

Section 1 – Introduction: Inclusion of paragraphs would make the introduction more reader-friendly.

ll. 34-35, 37-39 and 63-66 need references.

Wording “ductile”: I am not sure if this is the correct word to describe the structures. Are they really ductile, e.g. the perforated concrete blocks in l. 55?

Section 2 – Experimental conditions: What was the water depth during the experiments? Can you give details on the dolos used for the breakwater (dimension, scale)?

l. 99: offshore distance from where?

Figure 2: Can you add information on the dimension of the single elements, and the wave direction?

ll. 116-121: For what kind of structure was Cs chosen? What was the value?

l. 119: tan(beta) is the slope of what?

Table 2: can you explain the parameter h?

Section 3 – Results and discussion:

l. 159: I think, Figure 5 shows only the wave distributions after structure installation, not before. Please check.

l. 165: Figure 5 shows 0.8 for Case 2 and and 0.6 for Case 1. The text says the other way around. Please check.

ll. 176-188: Please explain what negative and positive values mean. Please check the text description to Figure 6. (ll.180-182 refer to Figure c and the middle part, ll. 185-187 refer to Figure a and the open inlet)

l. 197: do you mean “significant reduction in the flow rate at approximately x = 0 cm”?

ll. 204-205: Did the hybrid method prevent sediment transportation completely? This reads as if there was no sediment transportation at all.

Figure 8: orange font not readable

l. 246: can you show your results from the analysis with this equation?

ll. 247-249: where is this shown? Is this interpretation of the morphological analysis? I think one could improve the description of the results and more clearly separate the result description from the interpretation/discussion in section 3.3 (see also next point).

ll. 254-255: Figure 9b only shows that there was less erosion. That this is due to reduction of the return flow exiting offshore is interpretation/discussion, but cannot be directly seen from Figure 9b.

ll.289-290: Does the hybrid method prevent local scour completely?

Section 3.3: please discuss the different erosion patterns on both sides of the breakwater (can be seen in Figure 9a).

Figures 10: previously x=0cm was defined in the middle of the breakwater. Can you unify the definition of x? For the reader it would also be easier if the elevations in Figure 9 and 10 would have the same scale.

Table 3: please define negative and positive values.

ll. 309-330: please explain the parameters and add a reference and description of Figure 11. How can Yoff be calculated?

Section 4 – Conclusions: Do you expect model and scale effects in your investigations? Please discuss them in section 4 (or section 3).

Overall comment on figures: Maybe one could try to adapt the scale of the figures so that the font size is more uniform (compare e.g. Figure 11 and 8)

Author Response

Reply to Reviewer #1

We thank the reviewer 1 for careful review of our manuscript and thoughtful comments. We think these thorough comments and responses to the comments have made the paper stronger and more impressive. We have attempted to address your comments below as your comments are in italics and our responses are in boldface.

Author Response File: Author Response.docx

Reviewer 2 Report

The research has a great value and the experiment, and the results are relevant to improve the knowledge in the study field. I want to congratulate the authors to this study and in the next comments I want to help to improve the document for an easily read for the readers.

Lines 49 to 62. References 8 to 13 I believe that the reference should be appear close to author name. In each reference the number appear in different position. This problem appears in the final part of the text again.

The authors should be introduced various paragraphs in the introduction section, and in the rest of the text. Read the text in the current form is not easy and this is harmful for the research understanding.

Line 133: Remove “called a drone” and put only (UAV) the acronym of the name appears previously.

Figure 4. Change “Lidar” for “LiDAR”.

Figure 6. Put this figure close to the first appear in the text. Same for the Figure 9.

I believe that the authors should review the position of Figures and Equations because in some case their position is difficult for a correct paper reading.

It is necessary resume the Conclusions. This section should be a concise explanation of results. In this case the reader can not identify the keys in this section.

Author Response

Reply to Reviewer #2

We thank the reviewer 2 for careful review of our paper and helpful suggestions. Please see our responses to your comments underneath each point. We believe these thorough comments and responses to the comments have made the paper stronger and more useful.  We do truly appreciate the time and effort of the reviewer 2 again. Comments are in italics and our responses are in boldface.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Very pleased to see the improvement of the paper. Please just have a further look at the following two issues:

- The new Figure 5e shows Y=2.8 m. Table 1 gives Y=2.4 m. Which is correct?

- Please check the text description to Figure 6.: I think, ll.186-188 refer to Figure 6c and the middle part, ll. 192-194 refer to Figure 6a and the open inlet) (cf. Comment 12 of the first review round)

Author Response

Responses to Reviewers’ comments

Reply to Reviewer #1

Again, thanks for your careful comment. This review was also very helpful for us to our paper. Your scrupulous comment made us to study more about the field.

We think these thorough comments and responses to the comments have made the paper stronger and more impressive. We have attempted to address your comments below as your comments are in italics and our responses are in boldface.

[General comment]

Reviewer #1: Very pleased to see the improvement of the paper. Please just have a further look at the following two issues:

[Comment 1]

The new Figure 5e shows Y=2.8 m. Table 1 gives Y=2.4 m. Which is correct?

[Response 1]

Sorry for our mistake. We corrected the value Y in Table 1.

Table 1. Specification of the 3D hydraulic experiment

 [Comment 2]

Please check the text description to Figure 6.: I think, ll.186-188 refer to Figure 6c and the middle part, ll. 192-194 refer to Figure 6a and the open inlet) (cf. Comment 12 of the first review round)

[Response 2]

Thanks for your careful comment. We found that we referred wrong figure. We rechecked and revised as below:

[Page 7]

Figure 6(c) shows the flow rate distribution over the middle of the structure.

Figure 6(a) shows the flow rate distribution at the open inlet, which exhibited a strong return flow behind the structure and a decrease in the flow rate offshore.

Author Response File: Author Response.docx