Round 1

Reviewer 1 Report

The paper Assessing urban expansion based on optimal granularity in the Huaihe River Basin of China is interesting. The paper might have some value but currently, it is not properly written and lacks clarity.

The introduction section is sketchy and lacks critical details that would enable an understanding of the research problem. The authors have discussed different methods used to measure urban expansion without presenting the problem and context. In this context, the authors have not defined what is the measure(s) of urban expansion, or in other words, how do the authors define urban expansion and how do they measure it? Also, what is optimal granularity or how it is defined and why it is relevant to urban expansion?

 Further, no details on the study area is provided that would critically show the various contexts, the expansion processes and the extent of expansion occurring in the study area. The introduction section may be re-articulated making it with three clear sections or sub-sections- that include the introduction, Literature review and study context. Since the information provided in the introduction concerning the study context is more or less related the section 2 (The study context and data source), the introductions section and section 2 should be restructured and re-articulated.   

The literature review is embedded in the introduction section but the articulation lack coherency and basically is focused on the methods used to measure urban expansion. The authors while making it a separate section and should include aspects such as urban expansion, various processes and influential factors as well as various measures and methods used to measure it. Furthermore, the optimal granularity should also be discussed and the research gap should be presented.

Data and data sources should be under the section 3, research methods.

Section 3.1. Since the authors have not clearly defined optimal granularity previously, it is not clear how equations 1 and 2 measure optimal granularity. For example, what does E or L (area loss) represent concerning optimal granularity

Similarly, what do the measures mentioned in equations 3 and 4 linked to optimal granularity?

In other words, the authors as mentioned previously need to clearly discuss what urban expansion is, how it is measured (by what indicators), what is the optimal granularity and how the elements are measured by using different equations (e.g., 3 and 4) help to establish or measure the urban expansion. Further, the data collection methods, the data used, their suitability and data analysis methods should be clearly presented.

The authors have presented the results and discussions in detail. While the results could be appreciated, the problem is  that they have introduced many new indicators or elements such as total class area (CA), largest patch index (LPI),  perimeter-area fractal dimension (PAF- RAC),  mean patch size (MPS), patch density (PD), landscape shape index (LSI), inflexion points, Landscape index and so on  for the first time without any mention of them either in the problem formulation or in the methodology. As a result, the whole of the results and discussion sections are not clear.

Furthermore, the authors have introduced mathematical models for the Landscape index and made calculations (Tables 4 and 6), without any reference for such model estimation or development in the methodology section. Further, what are the implications of these calculations (linked to optimal granularity)? Also, what do the various functions used indicate in the curve fitting and why are they relevant? Why these models should be considered valid and useful? More importantly what data are used to make these model estimations? Similarly, it is not clear what the elements used in Table 5 indicate and how these values have been obtained. Overall, the results and discussion sections look incoherent and lack clarity.

Overall, although the paper might have some value, it suffers from problems related to structure, lack of clarity and methodological details. It needs significant improvement.

 

 

Author Response

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Reviewer 2 Report

Overview:

This paper examines a case study and theoretical analysis of a primary problem in landscape ecology research. The optimal granularity, which has often been ignored in the analysis of urban expansion and its landscape pattern is used as a basis to evaluate urban growth in the Huaihe River Basin of China.

The paper addresses an interesting and timely question. It presents a good and substantial amount of work and deserves publication. Although the quality of its content is esteemed, however, the following minor issues should be addressed before publishing it.

 Comments:

 1-The title could read better if it is as follows: “Urban expansion assessment based on optimal granularity in the Huaihe River Basin of China“

 2- “Section 2: Study area and data sources” should be moved to be under section “3 Research method”. Accordingly, the numbering of the sections and subsections will change.

 3-The following documents are worth citing in the introduction to widen your theoretical context and to show that you are well aware of the elsewhere urban development problems:

 

-Patias, N., et al. Sustainable urban development indicators in Great Britain from 2001 to 2016. Landscape and Urban Planning 214 (2021): 104148.

 

-Bouchair, A., et al. Compact cities as a response to the challenging local environmental constraints in hot arid lands of Algeria. Energy Procedia 42 (2013): 493-502.

Author Response

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Reviewer 3 Report

The is good effort but it requires following corrects before further going for the publications.

#The abstract requires editing with precise explanations.

#Introduction needs to be more focused.

# Methodology section needs to be reworked.

#Discussion is required to be validated.

#Add recent references.

 

 

Author Response

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Reviewer 4 Report

Overall and Major Comments

First of all, the research content of the article is still very rich, but because of the excessive research content, each research point is not in-depth. I think the analysis of the optimal granularity is actually a content worth studying. If authors study it in depth, it may support the whole paper. However, there are only a few paragraphs about the determination of the optimal granularity, and the determination of the inflection point is too subjective to convince me that it is the optimal granularity. In addition, what puzzles me most is whether this research is universal, or just an example. Is there a situation for me to find another landscape indices  and find a different inflection point as the optimal granularity?

 

Specific Comments

(1)   Line 6, Line 12: I think the authors need apply for institutional mailboxs, which are more formal for an article.

(2)   Line 14: “its landscape pattern”, what does “its” mean?

(3)   Line 15: “Haihe River Basin” → “the Huai River basin”, please consider.

(4)   Line 43: “Lu and Weng” → “Lu and Weng [7]” may be better.

(5)   Lines 34-56: Too many literatures are about the extraction of impervious surface, and only a few literatures are about urban land density. Please supplement more relevant literature.

(6)   Line 57: There is no transition from the above content (first paragraph).

(7)   Lines 69-71: “…, few have addressed the issue of the optimal granularity for use in urban expansion studies.” Is it true that no one has considered this issue? Academic research should not be too absolute. If no one is involved in this issue, is it not worth studying?

(8)   Line 73: “significant area loss”, the resolution of remote sensing images isn't that the highest resolution you can get. If you just look at this sentence and don't read the references, it will be puzzling.

(9)   Lines 72-73: The explanation of the meaning of the research is difficult to understand. Please note that the reader may not be a researcher in your field, but you should let him understand your expression.

(10)Lines 77-86: The content belongs to the research area.

(11)Lines 94-95: “spatial heterogeneities”. Why does spatial heterogeneity suddenly appear? You didn't mention this concept when you introduced the background.

(12)Line 99: “E 111°55′~121°25′ and N 30°55′~36°20′” → “111°55′E ~121°25′E  and 30°55′N ~36°20′N”.

(13)Line 100: “faces the Yellow Sea in the east”, “face” is appropriate ?

(14)Line 100: “covering” is appropriate ?

(15)Line 102: “km2” .

(16)Line 111: “favorable” is appropriate ?

(17)Lines 112-116: The purpose of the research is confusing to me. It has nothing to do with the optimal granularity.

(18)Line 117: The legend in Figure 1 is incomplete. What does red represent?

(19)Line 117: “Megacities”, where?

(20)Line 119: There are three big cities, but only one medium-sized city and one small city. The proportion is puzzling.

(21)Lines 119: Are they representative? Then the question arises. Is the optimal granularity related to the size of the city? If so, then the representativeness of the city is a question. If not, it is just a study of methods. Does it need so many cities?

(22)Lines 169, 174: Urban land density (Dens) , f(r) represents the urban land density. Do they mean the same thing?

(23)Lines 186-197: Is this part of the research method?

(24)Line 198: The determination of the inflection point is too subjective.

(25)Line 209: The picture is very beautiful, but I don't think it's appropriate to express it in this way.

Author Response

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Round 2

Reviewer 1 Report

The paper is significantly improved from the previous version. However, a few aspects need to clearly articulated.

(1) It is not clear how the curves fitted and as presented in Figure 6 and the results presented in Table 5 were obtained. No explicit or direct  references to this curve fitting and calculations (model estimation) shown in Table 5 in the methodology section are observed. 

(2) What is the implication of the results/models shown in Table 5? Are they models or results or model estimation parameters? If they are models then how can they be some numbers instead of equations? I understand the authors have used equation 4 to arrive at these, however, they need to clarify this aspect.

(3) Equation 3 and 5 are the same. It seems the authors have used equation 5 to calculate the values Alpha, c and D values. However, it is not clear how they have made the calculations as there are three unknowns to be calculated by using this equation (Not sure if I understood it properly). 

Needs a little bit of language editing to make it more readable.  

 

Author Response

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Reviewer 4 Report

I have no other suggestions.

Author Response

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Round 3

Reviewer 1 Report

The authors have addressed the concerens reasonably. The paper may be accepted.

Comments for author File: Comments.docx