Review Reports - Impacts of Urbanization on Drainage System Health and Sustainable Drainage Recommendations for Future Scenarios—A Small City Case in China

Round 1

Reviewer 1 Report

1- The author should have mentioned their innovation and its behind idea in the abstract and introduction section in more detail.

2- The tile of paper is too long and it does not display the content of the paper well, it is more appropriate to use a more concise and comprehensive title.

3- Line101, what do you mean by the urbanization rate? which index and formula do you use for urbanization rate?

4- Line 160, I can find the supplementary information file?

5- Table 2, the source of allocated weight is not clear. It need to be explain in more detail.

6- While the main aims of this study is to investigate the urbanization on drainage status in small area, I think the proportional item also should be including in table 2 to highlight the drainage character for example mean annual discharge or maximum (minimum) daily discharge at drainage system or even innovative item such as area of urban storm network.

7- Line 178, the abbreviation of WWTPs is not introduce before.

8- The source of weight in table 3 is not clear.

9- Line 190, I think it is better to picture out your research methodology with additional figure.

10- Line 196, the gray system should be defining or specified by references.

11- Line 208, did you use google earth history image or google earth engine?

12- Line 212, I cannot supplementary information file? did you submit the supplementary file?

13- Lines 210-214, it may be useful to picture put the land use or land use change across the study area.

14- Line 215, in which way did you model the land use pattern in the study area. How did you define CN parameter in each sub basin?

15- What is the necessity of Table 4 in the text of the article?

16- Line 288, Can climate change be considered and analyzed in these parameters?

Author Response

Thanks for your thinkful comments. Please see the attachment.

Response to Reviewer 1 Comments

1- The author should have mentioned their innovation and its behind idea in the abstract and introduction section in more detail.

Response 1:

Thanks for the great helpful comments! We have recognized that the innovation is not highlighted in the abstract and introduction. There are two innovative ideas in this paper. First, a evaluation framework for the urbanization and drainage system health is proposed based on model analysis and statistical methods. Second, gray models are used to predict the drainage system healthiness scores under different urbanization scenarios, thus giving suggestions for future urban drainage system construction. In the new revised version, we have updated the details of the innovation.

2- The tile of paper is too long and it does not display the content of the paper well, it is more appropriate to use a more concise and comprehensive title.

Response2:

This is a good suggestion. The main focus of this paper is to evaluate the changes of urbanization index and drainage system health index in Jinxi during 2009-2020, analyze the impacts, and predict drainage system health based on urbanization index of future scenarios. Considering of the main purpose, I has rewrited the title and modified it in the manuscript. The new title is Impacts of Urbanization on Drainage System Health and Sustainabile Recommendations for Future Scenarios, case study in a small city,China.

3- Line101, what do you mean by the urbanization rate? which index and formula do you use for urbanization rate?

Response3:

The urbanization rate here refers to the most widely accepted urbanization rate, which is the proportion of the urban population to the total population of the jurisdiction. To prevent confusion among readers, we have revised this text from urbanization rate to urban population proportion in the manuscript.

4- Line 160, I can find the supplementary information file?

Response4:

Supplementary Data had been attached in the last section of the original manuscript. I guess the editors perharps forgot to index it so that you could’t find it immediately. In the new revised edition, we have added an appendix instead of supplementary material, please check it.

5- Table 2, the source of allocated weight is not clear. It need to be explain in more detail.

Response5:

This is a very useful comment. We have changed the order of the sentences to make our readers more clear in the manuscript. The process of calculating the weights was added and explained first, and then the meaning of each dimensional weight represents were described. We used the data in Appendix Table A1 as input to obtain the subjective and objective weights using hierarchical analysis and entropy weighting method, respectively. The detailed method of allocating weights is explained in subsection 3.2.

Response6:

This comment is worth considering furtherly. We have indeed seen some articles that add indicators of drainage system characteristics to a comprehensive system of urbanization, just like what your comment shows. However, the main purpose of these articles is to explore the coupled and coordinated development relationship between urbanization and environment, energy and resources, etc. When we focus on the impact of urbanization on drainage system health, drainage system characteristics indicators are not suitable to be added to the urbanization evaluation index system, but to the drainage system health evaluation system as dependent variables. Actually, we did mention the scale of the drainage system, such as the density of the pipe network and the daily treatment capacity of the wastewater plant in Table 3 but not in Table 2.

7- Line 178, the abbreviation of WWTPs is not introduce before.

Response7:

Wastewater treatment plant （WWTP）is a relatively common abbreviated noun in the field of Environment. In order to make the abbreviations understandable to all readers, we have added the full name where it first appears. Thanks for this suggestion !

8- The source of weight in table 3 is not clear.

Response8:

This comment is similar to the fifth. We used the data in Appendix Table A2 as input to obtain the subjective and objective weights using hierarchical analysis and entropy weighting method, respectively. The weight calculation method is described specifically in subsection 3.2.

9- Line 190, I think it is better to picture out your research methodology with additional figure.

Response9:

The technology roadmap visually reflects the methodology of this article. We have added additional technology roadmaps in the revised manuscript. Thanks for your recommendation.

10- Line 196, the gray system should be defining or specified by references.

Response10:

This is an issue that we need to be concerned about. We have added a reference to the gray system model where it first appears.

11- Line 208, did you use google earth history image or google earth engine?

Response11:

In fact, we use Google's historical image product(2012-2020) whose the original data source is landsat7/8. In other words, Google helps us with the atmospheric correction, geographic alignment, and orthographic projection steps of the original remote sensing images. We have updated this statement in the manuscript.

12- Line 212, I cannot supplementary information file? did you submit the supplementary file?

Response12:

We really did. You can find the supplementary Data in the end part of the updated manuscript. In the new revised edition, we have added an appendix instead of supplementary material, please check it.

13- Lines 210-214, it may be useful to picture put the land use or land use change across the study area.

Response13:

Yes,it is. We put the picture of land use changes into the Supplementary Figure S1. Now you can find this figure in the Appendix Figure A1 .

14- Line 215, in which way did you model the land use pattern in the study area. How did you define CN parameter in each sub basin?

Response14:

Thanks. That's a thinkful question. All the types of land use can be set for each subcatchment in SWMM as long as the researcher knows the proportion of each type, just like the screenshot below this response. The different land use types differ in their ability to intercept pollution, resulting in varying runoff pollution in each catchment area. Meanwhile, different land uses have its own corresponding effects on the settings of key parameters. CN parameters are more frequently used in basin hydrological models but hardly mentioned in SWMM. There are similar hydrological parameters in swmm to represent infiltration and runoff, such as pervious area Manning factor, impervious area Manning factor, maximum/minimum infiltration rate, infiltration rate decay period, etc. Most of the hydrological parameters need to be selected at a suitable range according to the land use. The model can be put into use only after the parameters are calibrated and validated based on actual observations.

15- What is the necessity of Table 4 in the text of the article?

Response15:

SWMM is the key data calculation method to evaluate the of drainage system health(DHI). The impact of urbanization on the drainage system is directly reflected in the input parameters of the model. For example, the residential drainage baseline is closely relatied to the change of building area. The infiltration of rainwater is closely related to the percentage of pervious area. The parameters were not always the same between models as the city kept developing. And in the results and discussion section, both the trend of DHI and the mechanism of urbanization's impact on DHI need to be explained from the perspective of model input. In this paper, we build a series of updated SWMM models based on the actual situation in Jinxi, which represented 2010/2012/2014/2016/2018/2020, separately. In order to explain the result clearly, we should first tell the reader what the difference input conditions between these models is.

16- Line 288, Can climate change be considered and analyzed in these parameters?

Response16:

We have discussed whether climate change should have to be considered. The final answer is unnecessary because some research proves that the impact of climate change on urban runoff is significantly weaker than that from urban development. On the other hand, when we set up the future scenarios, we mainly consider four scenarios such as population growth, industrial upgrading, service industry progress, and urban regression in the next two decades. The impact of climate change on the city is almost negligible. But this is really an interesting research direction.

Here is the related paper I mention before. https://doi.org/10.1016/j.scitotenv.2018.12.184

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors analyzed the impact of urbanization on drainage system health under different scenarios. The reviewer suggests minor revisions before publication to "Sustainability".

1) In table 1, the reviewer did not understand "Production and operation divisions of WWTPs". Production might be a mistake of "Construction".

2) In table 2, "Ha" might be a mistake of "ha". Please check the unit of gas supply (Ton may be a mistake of m3). In addition, if gas supply and water supply are annual value, use "m3/y" instead of "m3".

3) In table 3, if the values for drainage system are annual values, use m3/y, d/y, h/y, m3/y instead of m3, d, h, m3.

4) The reviewer did not understand the caption of Table 4. What did the authors mean by "Differences"? Please add appropriate explanations.

5) In figure 4, the same correlation coefficients appear twice symmetrically in the figure. Generally speaking, triangle table is preferable to avoid duplicated description of the same numbers.

6) In the section of 4.4, the authors wrote "... measures must be taken ... " in each itemized section. In the abstract and in the conclusion, the authors wrote "... measures should be taken ... " These "must" and "should" are not appropriate as expressions for a research paper. The authors can rewrite these words and can replace with "... measures are favorable for sustainable development ..."for example.

Author Response

Thanks for your thinkful comments. Please see the attachment.

Response to Reviewer 2 Comments

1) In table 1, the reviewer did not understand "Production and operation divisions of WWTPs". Production might be a mistake of "Construction".

Response 1:

This is a small translation issue about the name. To understand clearly, we used Operation office of WWTPs instead of Production and operation divisions in the revision manuscript.

Response 2:

Thanks for your perceptive comments. After the double check, we changed all the potential unit problems as you said.

3) In table 3, if the values for drainage system are annual values, use m3/y, d/y, h/y, m3/y instead of m3, d, h, m3.

Response 3:

Thanks for your perceptive comments. After the double check, we changed all the potential unit problems as you said.

4) The reviewer did not understand the caption of Table 4. What did the authors mean by "Differences"? Please add appropriate explanations.

Response 4:

In fact, the difference refers to the different input settings between the of models (2010/2012/2014/2016 /2018/2020). Since most of the drainage system health indicators are generated from the simulation results of the models, we need to clearly elaborate the different inputs between the models so as to explain the causes of the changes in drainage system health. Now we have revised the title of the table for easy understanding.

5) In figure 4, the same correlation coefficients appear twice symmetrically in the figure. Generally speaking, triangle table is preferable to avoid duplicated description of the same numbers.

Response 5:

This is a good recommendation.We redrew the square heat map as a triangle type.

Response 6:

This brilliant advice has been adopted. Because all the suggestions we give in the conclusion are carried with uncertainty. We try to replace absolute words with milder ones with uncertainty, as you said. The specific corrections have been completed in the revised version.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

I think the manuscript is improving and the author can address the question well. But respond to 2 questions need more serious attention.

1-Response to question #5 is not convincing. Please provide more detailed on this issue. If you use experts to construct the AHP analysis, the statistical description should be mentioned.

2. Response to question #14 is not convincing. anyway, this is an important issue that should be addressed.

Author Response

Thanks for your updated comments！ Please see the attachment.

Author Response File: Author Response.pdf