Numerical Investigation on Wave-Overtopping at a Double-Dike Defence Structure in Response to Climate Change-Induced Sea Level Rise
Round 1
Reviewer 1 Report
The paper uses CFD to study overtopping on a wall representing a dike. Then the effect of different relative height are studied parametrically, and the changes in the relative height studied are related to the possible sea level rises under different scenarios. It looks partially artificial to formulate the problem in this way but still acceptable.
The introduction starts with climate change comments and then there is a paragraph about the situation in Norway. This is absolutely out of the scope of the discussion as Norway is a country not much liable to sea level rise and thus there is no justification for discussing the situation in that country, while for example, The Netherlands represents a much more critical situation. That paragraph should be removed as outside the scope and discussion of the paper.
In the literature review only refs 10 and 11 deal with the application of CFD, which is the main subject of the paper. This is not enough to convince the readers that this paper is filling any gap in the literature. A significant more extensive discussion of CFD papers that deal with this type of problem is required. The discussion should indicate the topics that have not been dealt with properly and explain how this paper will contribute.
Otherwise, this paper looks like an exercise in which a code was tested and applied to a problem as an example, which is a too simple example to justify publication
Author Response
Comments and Suggestions for Authors
The paper uses CFD to study overtopping on a wall representing a dike. Then the effect of different relative height are studied parametrically, and the changes in the relative height studied are related to the possible sea level rises under different scenarios. It looks partially artificial to formulate the problem in this way but still acceptable.
The introduction starts with climate change comments and then there is a paragraph about the situation in Norway. This is absolutely out of the scope of the discussion as Norway is a country not much liable to sea level rise and thus there is no justification for discussing the situation in that country, while for example, The Netherlands represents a much more critical situation. That paragraph should be removed as outside the scope and discussion of the paper.
Response: The discussion on Norway has been removed.
In the literature review only refs 10 and 11 deal with the application of CFD, which is the main subject of the paper. This is not enough to convince the readers that this paper is filling any gap in the literature. A significant more extensive discussion of CFD papers that deal with this type of problem is required. The discussion should indicate the topics that have not been dealt with properly and explain how this paper will contribute.
Response: More detailed discussion on the state-of-the-art CFD studies have been added in the introduction.
Otherwise, this paper looks like an exercise in which a code was tested and applied to a problem as an example, which is a too simple example to justify publication
Response: the motivation and novelty of introducing and faster alternative to CFD are also discussed in detail to address the significance of the work, see red texts in the revised manuscript.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript is devoted to an important and topical issue of climate change. In this form, the manuscript cannot be published. It is necessary to carry out a deep revision of the text. I will make the following remarks. 1. It is unclear where and how formulas (16)-(19) were obtained. 2. How will the analytical part be obtained in formulas (16)-(19)? 3. What numerical methods are used in the numerical integration of the equations of motion? After answering these questions, you can return to reviewing the manuscript.
Author Response
Reviewer 2:
Comments and Suggestions for Authors
The manuscript is devoted to an important and topical issue of climate change. In this form, the manuscript cannot be published. It is necessary to carry out a deep revision of the text. I will make the following remarks.
- It is unclear where and how formulas (16)-(19) were obtained.
Response: formulas (16)-(19) describe how the flow properties are prescribed in the wave generation zone following the references of Bihs et. al. (2016) and Jacobsen et. al. (2012), who implemented the methods in REEF3D and OpenFOAM respectively. These references are mentioned above equation (15), the references are also mentioned right above equation (16) now.
2. How will the analytical part be obtained in formulas (16)-(19)?
Response: The analytical parts of equation (16) - (19) are obtained from wave theory, for example, when one generated a 2nd Stokes wave, the theoretical values of 2nd Stokes wave are the analytical parts.
3. What numerical methods are used in the numerical integration of the equations of motion? After answering these questions, you can return to reviewing the manuscript.
Response: The governing equations are written in a differential form with a finite difference method. The solution for velocities is solved using Chorin’s projection method and the pressure is solved from Poisson equation following the Hypre Library. This information is added in the revised manuscript in red.
Author Response File: Author Response.pdf
Reviewer 3 Report
The main objective of the present study is to investigate wave overtopping numerically using a shallow water equation (SWE) based non-hydrostatic model REEF3D::SFLOW. The topic is important and interesting to the reader. The numerical methods are well explained. In addition, the numerical benchmarks and validation are presented. However, the novelty needs to be presented. The discussion and analysis need to be more profound. Therefore, the paper needs a revision and provides the following comments for correction.
1. I would strongly advise the author to add the literature related to numerical simulation of wave overtopping and rewrite their introduction by identifying the previous research gap. Moreover, the paper's novelty could be well stated.
2. The numerical error should be presented in detail between simulation and experiment.
3. The main topic is a numerical investigation on wave overtopping. Therefore, results and discussion should be expanded by describing the research's major findings numerically and comparing them to previous studies. In addition, the current research area's gaps must be highlighted, and future study directions must be presented.
4. This paper stated that the methods provide an efficient alternative to the Naiver-Stokes equation based solved. Therefore, the discussion about the statement needs to be presented.
Author Response
Reviewer 3:
Comments and Suggestions for Authors
The main objective of the present study is to investigate wave overtopping numerically using a shallow water equation (SWE) based non-hydrostatic model REEF3D::SFLOW. The topic is important and interesting to the reader. The numerical methods are well explained. In addition, the numerical benchmarks and validation are presented. However, the novelty needs to be presented. The discussion and analysis need to be more profound. Therefore, the paper needs a revision and provides the following comments for correction.
1. I would strongly advise the author to add the literature related to numerical simulation of wave overtopping and rewrite their introduction by identifying the previous research gap. Moreover, the paper's novelty could be well stated.
Response: More detailed discussion on the state-of-the-art CFD studies and the motivation and novelty of introducing a faster alternative to CFD is also discussed to address the significance of the work in the introduction section, see red texts in the revised manuscript.
2. The numerical error should be presented in detail between simulation and experiment.
Response: quantified numerical errors are added in the result section, see texts in red.
3. The main topic is a numerical investigation on wave overtopping. Therefore, results and discussion should be expanded by describing the research's major findings numerically and comparing them to previous studies. In addition, the current research area's gaps must be highlighted, and future study directions must be presented.
This paper stated that the methods provide an efficient alternative to the Naiver-Stokes equation based solved. Therefore, the discussion about the statement needs to be presented.
Response: A new plot showing the time series of water surface over structure crests is added as the new Fig.9 to support the findings of overtopping. The overtopping volume error is added to Figure 10.
More detailed discussion on the state-of-the-art CFD studies and research gap and the significance of introducing a faster alternative to CFD are also discussed to address the significance of the work in the introduction and conclusion sections, see red texts in the revised manuscript.
The comparison of computation speed between SFLOW and CFD is shown in line 223-333.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The authors have responded to the main aspects that I have raised. I see that the paper has been improved and could be accepted.
However there are formating aspects that need to be handled before final acceptance.
A detailed spell check should be done as several bugs are still present in the text such as for example Naiver-Stokes
The reference Van der Meer (1998) needs to be given a sequential number
Author Response
The authors have underwent a new round of proofread and fixed several spelling and grammar mistakes through the manuscript. The reference of van de Meer is also updated.
Author Response File: Author Response.pdf
Reviewer 3 Report
I think the paper can be accepted now
Author Response
The author thank the reviewer for the approval and hope the manuscript has a positive impact on the coastal engineering community.
