Deriving Optimal Analysis Method for Road Surface Runoff with Change in Basin Geometry and Grate Inlet Installation

Round 1

Reviewer 1 Report

In this study, the simplified and modified basin geometries, road surface and gutter flow travel times, and inlet interception efficiency are taken as the key parameters under various road conditions, and the road surface-runoffs analysis is carried out, and then an optimal road surface-runoff analysis method is proposed, which can be used as a useful resource for the design of road drainage system. I see that the author has made great efforts in parameter selection and experimental design. The author also analyzes the influence of each parameter in the analysis experiment results which reflect the topographic conditions of urban roads. Nevertheless, there are still some contents that need to be improved or discussed in this paper. I suggest that this manuscript be published after a  moderate revision. I have the following comments: 

(1) The topographical road conditions of this study are set as follows: width (6 m), longitudinal slope of road (2–10%), road surface slope (2%), and transverse slope of gutter (2–7%) .Although the author cited previous studies [11] on line 162, is this setting representative and practical? I suggest further explanation. 

(2) From line 245 to line 247, the author sets the interval of the gutter to 20 meters and 40 meters. Why is it so set? I suggest further explanation. At the same time, is it necessary to consider the scenario of non fixed intervals? 

(3) In Section 3.1, lines 257 to 258, the calculated travel time is used as the rainfall duration to estimate the total pavement flow. How to consider the error? You did not provide a reference for this method. I think the author has the responsibility to make readers have confidence in the methodology of the paper. Please prove that this choice is correct and dispel readers' doubts about this choice. 

(4) In section 3.1.2, lines 300 to 302, the author points out that the method similar to that in case 4 is considered to be the most suitable for the actual runoff analysis reflecting the longitudinal and transverse slopes of the road. I suggest more discussion and elaboration, and even comparison with the actual road surface runoff scenario to verify this view.(5) Please rephrase some sentences to make it more clear to the wide audience. There are some other minor mistakes.  The reference styles are suggested to be double-checked.

Author Response

1. The topographical road conditions of this study are set as follows: width (6 m), longitudinal slope of road (2–10%), road surface slope (2%), and transverse slope of gutter (2–7%). Although the author cited previous studies [11] on line 162, is this setting representative and practical? I suggest further explanation.

 

Reply 1: Thank you for your comment. The road conditions were determined by referring to the design criteria of the United States, Japan, and Korea and previous studies. I believe it efficiently covers the conditions presented in the design criteria. Moreover, related references have been added and cited in the main text (lines 166-168).

 

2. From line 245 to line 247, the author sets the interval of the gutter to 20 meters and 40 meters. Why is it so set? I suggest further explanation. At the same time, is it necessary to consider the scenario of non fixed intervals?

 

Reply 2: Thank you for your comment. In many Asian countries, 20 m is considered a design criterion, or it is selected appropriately at intervals of 5 to 40 m, and the actual field survey in Korea confirmed the installation status at intervals of 40 m. In the United States, they suggest using calculation processes and then accordingly select the calculated design intervals. Therefore, it is important to select the appropriate intervals. This study was conducted by selecting installation intervals of 20 m and 40 m. Additional explanations and references have been added in Section 2.5.

 

3. In Section 3.1, lines 257 to 258, the calculated travel time is used as the rainfall duration to estimate the total pavement flow. How to consider the error? You did not provide a reference for this method. I think the author has the responsibility to make readers have confidence in the methodology of the paper. Please prove that this choice is correct and dispel readers' doubts about this choice.

 

Reply 3: Thank you for your comments. To clarify the selection of flow travel time as rainfall intensity duration, lines 279-280 have been revised. The calculation method and reason are explained in detail in Section 2.4 and the third paragraph of Introduction to ensure clarity.

 

4. In section 3.1.2, lines 300 to 302, the author points out that the method similar to that in case 4 is considered to be the most suitable for the actual runoff analysis reflecting the longitudinal and transverse slopes of the road. I suggest more discussion and elaboration, and even comparison with the actual road surface runoff scenario to verify this view.

 

Reply 4: Thank you for your comment. Case 4 considers the road surface travel time of the modified basin area not considered earlier. The sentence has been revised to indicate that a new approach has been considered. In the Introduction, sentences have been added to indicate that this approach is a new attempt (lines 46-49; lines 71-74). An analytical experiment was conducted in this study, and future research is required to verify the method proposed in this study with actual data; this has been mentioned in Conclusions (lines 399-402).

 

5. Please rephrase some sentences to make it more clear to the wide audience. There are some other minor mistakes. The reference styles are suggested to be double-checked.

 

Reply 5: Thank for your comment. The entire sentences of the manuscript and reference styles have been modified.

 

Reviewer 2 Report

Road Surface Runoff is a major part of urban runoff. It is important to find an optimal analysis method for road surface runoff calculation. The research topic is very important. Also I see some innovation there. I think is it can be accepted after revision. The suggestion for improvement include:

1.     In introduction part, it is suggest to add some sentences and references to highlight the significant meanings of Deriving Optimal Analysis Method for Road Surface Runoff. How and where the optimal method can be used?  Some utilization scenarios can be discussed.

2.     It is said that “The topographical road conditions were set as follows: width (6 m), longitudinal slope of road (2–10%), road surface slope (2%), and transverse slope of gutter (2–7%)”. Please explain the reasons of the setting.

3.     How to validate the method you proposed and how to prove its advantages over existing various approaches? Is it possible to obtain real data to validate the apporach?

4.     For technical paper, short and simple sentence is more understandable and concise. I suggest to revise many sentences to make it clearer. Such as, “the runoff is drained through grate inlets on gutters due to changes in the urban runoff environment caused by continuous urbanization and industrialization”.

5.     In conclusions, it is said that“The geomorphology of the road drainage basin changes when considering the different slope conditions of the road. The higher the slope of the road, the longer the flow path-length ℓ. The slope and surface travel time both increased.”it is true that higher the slope of the road the longer the flow path-length. However, higher the slope of the road the higher the flow velocity. In this context, it is not sure that surface travel time increased along with the higher slope. Please explain more.

6.     I know that there is a special issue called "Urban Runoff Control and Sponge City Construction”(https://www.mdpi.com/journal/water/special_issues/UrbanRunoff_Control2). I think this manuscript fit this special issue and suggest move to this special issue to increase more readership.

Author Response

1. In introduction part, it is suggest to add some sentences and references to highlight the significant meanings of Deriving Optimal Analysis Method for Road Surface Runoff. How and where the optimal method can be used? Some utilization scenarios can be discussed.

 

Reply 1: Thank you for your comment. In the Introduction, sentences have been added to indicate that this approach is a new attempt (lines 46-49; lines 71-74). The applicability of this study has also been added.

 

2. It is said that “The topographical road conditions were set as follows: width (6 m), longitudinal slope of road (2–10%), road surface slope (2%), and transverse slope of gutter (2–7%)”. Please explain the reasons of the setting.

 

Reply 2: Thank you for your comment. The road conditions were determined by referring to the design criteria of the United States, Japan, and Korea and previous studies. I believe it efficiently covers the conditions presented in the design criteria. Moreover, related references have been added and cited in the main text (lines 166-168).

 

3. How to validate the method you proposed and how to prove its advantages over existing various approaches? Is it possible to obtain real data to validate the approach?

 

Reply 3: Thank you for your comment. An analytical experiment was conducted in this study, and future research is required to verify the method proposed in this study with actual data; this has been mentioned in the Conclusions (lines 397-402).

 

4. For technical paper, short and simple sentence is more understandable and concise. I suggest to revise many sentences to make it clearer. Such as, “the runoff is drained through grate inlets on gutters due to changes in the urban runoff environment caused by continuous urbanization and industrialization”.

 

Reply 4: Thank you for your comment. The entire sentences of the manuscript have been modified for improved clarity.

 

5. In conclusions, it is said that“The geomorphology of the road drainage basin changes when considering the different slope conditions of the road. The higher the slope of the road, the longer the flow path-length ℓ. The slope and surface travel time both increased.”it is true that higher the slope of the road the longer the flow path-length. However, higher the slope of the road the higher the flow velocity. In this context, it is not sure that surface travel time increased along with the higher slope. Please explain more.

 

Reply 5: Thank you for your comment. The road surface travel time is calculated using the Kerby equation (Eq. 9 in this study). At this instant, it was confirmed that the effect of the flow path-length (ℓ) was more significant than the road slope (s). Consequently, the travel time increased. This has been mentioned in the Conclusions (lines 380-389).

 

6. I know that there is a special issue called "Urban Runoff Control and Sponge City Construction”(https://www.mdpi.com/journal/water/special_issues/UrbanRunoff_Control2). I think this manuscript fit this special issue and suggest move to this special issue to increase more readership.

 

Reply 6: Thank you for your comment. This has been discussed with the journal editor.

Reviewer 3 Report

 

The paper presents an interesting study on the introduction of an optimal method for the analysis of road surface runoff, useful for road design.

The main objectives of the paper are clear and supported by data, references, and explanations of the methodological steps, but the novelty/contribution of this study to the previous extensive research in the field needs to be more clearly emphasized in the abstract and introduction. This should be done especially in the introduction, where it should be highlighted what the contributions and methodological improvements are compared to Jo et al [9] and Kim et al [11], which are the methodological foundations for this work.

Also, I would suggest that the structure of the paper should be reorganized to better understand the methodological steps and that Section 3.2 be presented in Section 2 Methodology and instead of the current Section 3.2, there should be a brief discussion of the superiority of the presented methodology over previous research based on the experimental results presented in this study.

Overall, this is an interesting research paper worth publishing and since the structure of the paper should be reorganized, I would suggest this paper for major revision.

 

Specific comments: 

Introduction - it would be beneficial for the readers to add a sentence/table with a list of variables related to road surface runoff and their influence on the process (from the conclusions of the references presented in introduction).

In the description of Table 1 - please include a reference and note that it is from a previous study [11]. And describe it as "experimental road conditions" so that it is consistent with the description of Table 2.

In Section 3. please emphasise at the end that of section list of methodological steps that are newly developed compared to previous studies [9] and [11].

In section 4 Results, percentage of discharge reduction in regard to slope changes / runoff  time changes would be more useful to readers

In Figure 7, the intercepted discharge from the description is not shown in the figure. Flow depth and discharge, while related, are two different hydraulic parameters, and the authors should be more specific in describing the results. The same comments about flow depth and discharge apply to the description of the methodological steps and the presentation of results in Sections 2 and 3.

Please comment on travel time results not only as change in absolute values in minutes, but also as relative change (e.g., in L377-380 in the conclusion).

 

Author Response

The paper presents an interesting study on the introduction of an optimal method for the analysis of road surface runoff, useful for road design.

The main objectives of the paper are clear and supported by data, references, and explanations of the methodological steps, but the novelty/contribution of this study to the previous extensive research in the field needs to be more clearly emphasized in the abstract and introduction. This should be done especially in the introduction, where it should be highlighted what the contributions and methodological improvements are compared to Jo et al [9] and Kim et al [11], which are the methodological foundations for this work.

Also, I would suggest that the structure of the paper should be reorganized to better understand the methodological steps and that Section 3.2 be presented in Section 2 Methodology and instead of the current Section 3.2, there should be a brief discussion of the superiority of the presented methodology over previous research based on the experimental results presented in this study.

Overall, this is an interesting research paper worth publishing and since the structure of the paper should be reorganized, I would suggest this paper for major revision.

 

Thank you for your comments. An analytical experiment was conducted in this study, and future research to verify the method proposed in this study with actual data is required; this has been mentioned in the Conclusions. In addition, sentences have been added in the Introduction to indicate that this approach is physically reasonable and a new attempt.

Additionally, Section 3.2 has been incorporated into Section 2.5, and more detailed conclusions are added in Section 3.2 to indicate the validity of this method.

 

1. Introduction - it would be beneficial for the readers to add a sentence/table with a list of variables related to road surface runoff and their influence on the process (from the conclusions of the references presented in introduction).

 

Reply 1: Thank you for your comment. In the Introduction, sentences have been added to indicate that this approach is a new attempt. The applicability of this study has also been added.

 

2. In the description of Table 1 - please include a reference and note that it is from a previous study [11]. And describe it as "experimental road conditions" so that it is consistent with the description of Table 2.

 

Reply 2: Thank you for your comment. The description of Table 1 has been modified so that it is consistent with that of Table 2. The road conditions were determined by referring to the design criteria of the United States, Japan, and Korea and previous studies. I believe it efficiently covers the conditions presented in the design criteria. Related references have been added and cited in the main text.

 

3. In Section 3. please emphasise at the end that of section list of methodological steps that are newly developed compared to previous studies [9] and [11].

 

Reply 3: Thank you for your comment. Previous studies [9] and [11] have improved a single road segment runoff analysis through analytical studies and hydraulic experiments. In this study, a novel approach was proposed by considering these variables in a complex manner under the continuous road segments. Additional information has been added in Introduction to explain this.

 

4. In section 4 Results, percentage of discharge reduction in regard to slope changes / runoff time changes would be more useful to readers

 

Reply 4: Thank you for your comment. The explanation about the percentage of discharge reductions has been added in Conclusion.

 

5. In Figure 7, the intercepted discharge from the description is not shown in the figure. Flow depth and discharge, while related, are two different hydraulic parameters, and the authors should be more specific in describing the results. The same comments about flow depth and discharge apply to the description of the methodological steps and the presentation of results in Sections 2 and 3.

 

Reply 5: Thank you for your comment. For the safe design of roads, first, the travel time of the road surface is calculated, which is then used as the critical rainfall intensity duration to calculate the road surface discharge. However, the flow depth varies according to the road slope conditions even with the same discharge. Therefore, travel time, flow discharge, and flow depth were sequentially proposed in this study. To explain this more clearly, detailed explanations related to the flow depth have been added in Figure 7.

 

6. Please comment on travel time results not only as change in absolute values in minutes, but also as relative change (e.g., in L377-380 in the conclusion).

 

Reply 6: Thank you for your comment. The relative change in travel time has been added in Conclusion.

Round 2

Reviewer 1 Report

I would like to thank the authors for answering all my questions and addressing all my concerns in the revised version of the paper. I am satisfied with the revised version of the paper. In my opinion, the revised manuscript has been greatly improved and is worthy of publication.

Author Response

Thank you for your comments.

Reviewer 2 Report

The authors have addressed some reviewer’s comments and make improvement. However, I still have a few suggestions to authors. I think the manuscript still need some revision before publication.

1.     Road runoff is an important issue along with urbanization. How to deal with this issue, different strategy and solution were proposed in difference counties, such as LID, WSUD, and Sponge city. In order to increase the international readership, it is suggested to mention these strategies in introduction part.

2.     In the manuscript, the topographical road conditions were set as follows: width (6 m), longitudinal slope of road (2–10%), road surface slope (2%), and transverse slope of gutter (2–7%)”. Author replied that the road conditions were determined by referring to the design criteria of the United States, Japan, and Korea and previous studies. It is fine. But are the research results still true in other topographical road conditions? Please explain.

3.     To verify the method proposed in this study with actual data is very important. I still suggest author improve this part. Only theoretical analysis is not persuadable.

In addition, as to the related special issue, author replied that this has been discussed with the journal editor. What is the result of discussion?

Author Response

Thank you for your comments.

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

The authors have responded adequately to all my comments and have improved the manuscript. I suggest paper to be accepted in present form.

Author Response

Thank you for your comments.