Review Reports

Round 1

Reviewer 1 Report

The manuscript is improved and can be accepted for publication. However, the novelty of this paper is limited. Please update some minor issues before the final publication.

1. The catchment polygon in figure 1 should be hollow so that the background DEM could be seen. The texts in administrative boundaries can be made bigger to make them easily readable.
2. Acronyms used in figure 2 should b either described in figure or captions, such as DEM, HSG
3. Figure 3 has a missing scale bar.
4. After figure 3 the figure number should be figure 4. please resolve them.

If possible, try to validate the results. Can you get any insights from satellite-based inundation or runoff? The main drawback of the current paper is the lack of validity.

 

Author Response

Dear reviewer,

Kindly find the attached file.

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript entitled “Impact of Land Use Change due to Urbanisation on surface run- off using GIS based SCS-CN method: A case study of Xiamen city”, analyses the impact of land use change on surface runoff using the Soil Conservation Service Curve Number (SCS-CN) method within a Geographic Information System. The study deals with the period of urban development from 1980 to 2015 in Xiamen, China.

 

Broad comments 

-Authors should explain why they chose the time period 1980-2015. Why not reaching 2020? And also, include the reason for splitting into the periods: 1980-1990, 1990-2005, 2005-2015.

-Figure 4 must be revised, and the consequent Figures and Tables generated after it.

-Discussion must be enhanced.

 

Specific comments 

-Line 5: no affiliation is mentioned for the author Shengping Ding

 -Lines 19-21: revise the sentence, connectors are missing.

-Line 32: all the Keywords are already included in the Title. Please provide other words.

-Lines 91-97: authors must explain the reason for choosing the period 1980-2015. Why starting in 1980? And why not including up to 2020?

-Figure 1: modify the catchment color, since it covers the DEM.

- Lines 115-118: try to use only 1 of the 2 sentences, because they bring almost the same information.

-Figure 2: why using “Soil type Map Landsat 8” in the top right. Please explain if authors used Landsat 8 for soil?

-Line 131: please include a description of each of the 8 categories of land use. This will help the reading of the manuscript.

-Lines 153-163: revise the paragraph, some sentences must be checked for grammar.

-Lines 166-172: it would be appropriated that the authors include an explanation of why they chose only 1 meteorological station, considering that the study area covers 1699 km²

No spatial variation in rainfall is considered?

-Lines 178-185: check plural/singular along the paragraph.

-Line 203: if authors mention the value of 0.05 for the abstraction coefficient in urbanized catchments, why did they choose 0.2 for the whole study area?

-Line 153-163: please include a description of each soil type, in order to enhance understanding.

-Figure 3: include an explanation of why choosing HSG D for water bodies. Please mention References for this criterion.

-Lines 294-296: revise sentences. Some words are repeated.

-Line329: I believe it refers to Figure 3 instead of Figure 5.

-Figure 4: this Figure must be revised: a) there is a Yellow color, not present in the Legend; b) why choosing those rangers of runoff and not others?; c) according to this Figure, the year 1990 has more runoff than 2005, is that correct?

-Line 361: it is mentioned Figure 8, but it is not on the manuscript.

-Line 424: it is mentioned Figure 9.

-Line 433: try to improve the Discussion Section.

-Line 467-470: explain the role of slope. And please try to associate the results of this paper with the different slopes in the area, and how they might interact.

-Description showed in Table A1 of the Appendix should be included in the text.

Author Response

Dear Reviewer,

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear Authors! I with interest read your article entitled: “Impact of Land Use Change due to Urbanisation on surface runoff using GIS based SCS-CN method: A case study of Xiamen city”. The topic of your study fits to Land journal scope. I have some suggestions and comments.

1. In Title better indicate that the study area is a southeastern part of China in Fujian Province. Not so many people know where Xiamen located is. Also in the Abstract please add a description that Xiamen is located in Fujian Province, southeastern part of China.
2. L. 51. Please add the examples of “impervious surfaces”. Asphalt, concrete, buildings and etc.?
3. Figure 1. It will be more informative if separate the catchment map and elevation map. Thus, the readers could see the catchments and elevation of study area apart.
4. Figure 3. Does in your study area a “Soil type A with high infiltration rate” not exist? You know that soil texture of A type HSG are sand, loamy sand, or sandy loam. And soils with such texture have high water permeability. Probably, the particle size distribution of soil in some areas of the study site have dominant sand fractions. For example, coast areas.
5. L. 441. “The high values of runoff gradually expanded outside Xiamen Island and were mainly distributed in coastal and bay areas”. Such statement seems contradictory. As I mentioned before, soils with sandy texture usually have a high infiltration rate.
6. In Abstract please add the way/methods which you suggest for reducing the runoff in conditions of urbanization.

Author Response

Dear Reviewer,

Kindly find the attached file.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

I believe the authors have improved the manuscript, paying attention to the comments of all the reviewers.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

The authors quantified impacts of several land use types, which are considered GI, on surface runoff in Xiamen city over the time. The applied the SCS method with design rain depths to estimate surface runoff across the city area. Impact of GI is evaluated by comparing simulated runoff to the runoff that would be generated if all GI surfaces were totally impermeable.

General Comments

There are two major concerns about this manuscript: (1) novelty, and (2) incomplete description of the methodology. Therefore, I strongly recommend the authors to:

1. Rephrase the Introduction and Discussion sections to clearly emphasise novelty and contribution of this study.
2. Enhance the Methodology section to

Specific comments are elaborated below; hopefully, they will help the authors to resolve the two key issues and improve the manuscript. The attached PDF also indicates key issues of the manuscript, but also contains some suggestions on wording. I sincerely hope that the authors will find the attached PDF helpful.

Specific Comments

1. ABSTRACT does not provide sufficient information on what is done in the paper and what the novelty of the paper is. Also, reduction in runoff is mentioned, while the results (e.g., Figures 6 and 7) show that an increase in design runoff due to urbanisation occurs over time. Please clarify this.
2. This section lacks flow: the authors firstly describe urbanisation impacts on hydrologic cycle and briefly bring up green infrastructure (GI), then talk about the models, and then proceed with describing how GI affects water cycle in urban environments. This section would considerably benefit from rearranging some paragraphs to improve overall flow. Most importantly, this section lacks a paragraph that clearly states novelty and contributions of this paper (e.g., what makes this study different from the ones that have been previously conducted for this area). I strongly recommend the authors to present the novelty in an individual paragraphs, rather than spreading it thin over several paragraphs.
3. METHODOLOGY
   1. DESIGN RAINFALL. The authors should explain what is the duration of the design rainfall (daily?), and elaborate on how is this particular duration selected. Is the rainfall intensity constant or time-varying, and if it vary in time, how is the design hyetograph formed (e.g., by employing the alternating block method)? The considered area is quite large, yet data from only one meteorological gauge are used. Therefore the authors should touch upon the issue of spatial heterogeneity in rainfall. What distribution is used for design rain depths computation? Are the same rain depths used for simulations in all four considered years, or were estimated for each year (1980, 1990, 2005 and 2015)?
   2. THE SCS METHOD. It is unclear if the SCS method is applied in a spatially-lumped or fully-distributed manner, as Figure 6 suggests. What is the spatial unit? This has to be clarified. The authors should explain which value of initial abstraction they adopted. At which time step is the SCS method used (e.g., with total daily rainfall or rainfall mass curves were employed)? There are also some comments on explanation of the method in the attached PDF that have to be addressed.
   3. RUNOFF REDUCTION CALCULATION. In my opinion, the runoff reduction should be defined at the very beginning of this paragraph. It is a bit confusing, because it might sound like the urbanisation led to a decrease in runoff over time. I suggest the authors (here and in few comments in the attached PDF) to clearly define this term.
      All variables have to be explicitly declared, and notations have to be consistent across the equations (see comments in the attached PDF). Impacts of change in land use and GI on runoff not sufficiently elaborated: how do you compare impacts across different years (e.g., in 2005 in comparison to 2015)? This should be elaborated.
4. Figures 4 and 5 show the same result, and perhaps one of them could be omitted.
5. DISCUSSION
   1. This section should contain a comparison of the methods used in this study, and the results obtained, to the previous studies. In this way, a contribution of this study can be proven.
   2. The authors should also discuss on (1) is the GI area key factor for storing surface runoff, or their spatial distribution can contribute to more effective water storing, and (2) which GI should be preferred as more effective or feasible (e.g., one could expect that one acre of forest or grassland would be more effective that the same area of cultivated land)? What would be the recommendations for e.g., spatial planning in this particular area (e.g., in which areas is the greatest increase in surface runoff observed; where GI would mostly contribute to surface runoff storing, etc.)? Also, the authors should discuss how uncertainties in CN estimation could affect their results.
6. MANUSCRIPT OVERALL CLARITY. There are numerous issues with the use of English in this manuscript. Therefore, the authors are encouraged to ask a professional interpreter or a native speaker to help them with the language. The notation has to be consistent through the manuscript, and should be consistently applied in the equations (please see comments in the attached PDF). I would also suggest the authors to change the way that return periods are denoted in the manuscript.

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

In the attached file 

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

The authors present an interesting and comprehensive investigation of the impact of land use and green infrastructure change on surface runoff. However, the current study is only a case study of Xiamen city, China which may or may not represent the regional or global picture. The present research deserves an outreach as rapid urbanization adversely affects the entire hydrologic regime of urban settings. These adverse impacts recurrently affect a dense population exposed to these extremes.

The authors used Landsat images of different periods and discussed the changing green infrastructure and land use and their association with surface runoff. However, I could find there are many occasions, revisions and improvements are needed. I compiled a list including recommendations and questions to the authors.

 

Abstract:

Line 16: Illustrate some key adverse effects of rapid urbanization.

Line 17 – 18: expanding built-up areas and green shrinking green spaces are a part of land-use changes. I suggest rewriting the sentence 16-18. It Maybe something as below:

Rapid urban expansion and shrinkage of green spaces are noticeable land-use changes in urban settings, which have adverse effects on the entire hydrologic regime, such as flood peak intensification and reduction in infiltration, ………

Line 19: What does green infrastructure mean? Please elaborate concisely before a first occurrence.

Line 20: Mention the method of land classification employed for Landsat imageries

Line 22: 5a, 10a, 20a, and 50a. Is it a universal way to provide 'a' for return period year representation? Even if so, I prefer to provide meaning at its first occurrence.

How did you validate the runoff? It is better to mention in the abstract concisely.

 

Introduction:

Line 58: It is still not clear what does green infrastructure mean? I suggest authors add concisely. Maybe bring Line 84-85 here.

Line 96-97: It seems it is redundantly being stated again and again.

Line 111 – 112: Line 97-99 states such effects are widely studied, and here it is mentioned again only limited studies focused on this issue. Please try to highlight the need for study and research gaps more effectively. Consider strengthening the innovative part of the present study in the light of previous researches.

Line 122: Full form of GIS is not needed. The only acronym should be enough since it has already been mentioned at first occurrence (refer to Line 80). Please check for other acronyms too.

Line 123: land-use change and GI change == > land use and GI change

 

Overall introduction section lacks the particular storyline that tells the need of the study for this area. If the research objective is focused on the selected city, please highlight why the site was chosen concisely in the introduction. If the aim is to find the association of land use and GI changes with surface runoff, please highlight the method to quantify and associate these factors.

 

Material and Methods:

Line 158: It's better to mention the Landsat version for respective years.

Line 160: What method was used for land use classification, and how was the accuracy?

Line 167: What is the spatial resolution of soil data?

Line 173: Is it daily rainfall time series? And, does table 1 represent the rainfall depth at one day in different return periods. Please mention the unit in the text and table. Please confirm the use of 5a, 10a, 20a, and 50a instead of 5, 10, 20, and 50 years. Please mention which method was used to estimate different return periods? And say why that method was used. There are many methods to estimate return period rainfall.

 

Overall, I find the validation of simulated surface runoff is missing. How can we be sure of the estimated surface runoff? And it seems the simulation is conducted on a daily scale. Is it okay for the urban setting to analyze on daily average surface runoff?

Importantly, initial abstraction is dependent on multiple factors. Different land-use types have different travel times. The simulation uses only one-day rainfall (for different return periods), how these initial settings are used. If daily time series were used, these initial conditions would replicate the real scenario after a warming period during simulation.

 

Results:

Line 339: How did you assess the increase of rainfall intensity? I believe this study compares the same rainfall intensity for different land-use types in four periods.

Line 342: It is obvious that with increasing rainfall return periods, runoff depth will increase. This fact is not necessary to mention. Or try to highlight the quantification of changes of runoff depth with respect to baseline for different return period rainfall. It may be insightful to find how sensitive are proportional change during an increase in rainfall return periods.

 

Overall I could not find noticeable runoff depth changes based on the difference in land-use types. Can you plot change with respect to 1980 in figure 6 and % change with respect to 1980 in figure 7? Try to report such % changes in different return periods and highlight the discussion based on what you find for low and high return period rainfall.

 

Discussions:

In general, the curve number should be calibrated based on observed surface runoff. Before running the model based on different return periods, please try to run on yearly maximum rainfall for other years and try to validate the model. If possible, try running with some antecedent rainfall information at least for 10-15 days for one event. By doing so, the curve numbers would effectively replicate the real scenario. Later, with that calibrated curve numbers, different return period rainfall should be inputted.

 

Conclusions:

Line 470-471: With increasing return periods, runoff depth will increase. This is a fact. There is no need to research this one. I believe this study's objective is to quantify the impact of land-use change on surface runoff.

 

Overall, I recommend that the authors rewrite the manuscript after a clear association between surface runoff and land-use changes. Otherwise, focus on land-use changes, validate land use classifications, and try to find the reasons behind land-use changes.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Land use is OK, and that's the most valuable part. I still think that the data is very coarse-grained, the method is very simplified, no modeling software was used, just a simple CN calculation, so for example the slope does not enter to the modeling result, nor the arrangement of the surrounding ecosystems (inflow from the environment) 

Reviewer 3 Report

Continuing to an earlier comment, I recommend that the authors rewrite the manuscript after a clear association between surface runoff and land-use changes.

Otherwise, focus on only land-use changes, validate land use classifications, and try to find the reasons behind land-use changes.

I could not see visible changes in a surface runoff with respect to land use alteration. I could see a similar range of % change of surface runoff in Table A4, which is the main highlight of the study. It should be in the main text.

I assume there should be a visible alteration of surface runoff (in % change) with respect to alteration in land-use changes.  

And, regarding the validation of the model, authors can use the known extreme rainfall of the latest period and compare it with satellite-based inundation patterns. The lowest value of surface runoff shown in Figure 6 is 172 mm (i.e., 17.2 cm). Is it practically correct? Therefore, the validity of the model is questionable.