Measuring the Urban Sprawl of a Mega-Urban Agglomeration Area Based on Multi-Dimensions with a Mechanical Equilibrium Model: A Case Study of the Yangtze River Delta, China
Round 1
Reviewer 1 Report
The article examines "efficient" and "inefficient" urban sprawl by applying the model to 17 urban agglomerations in the Yangtze River Delta (YRD). The authors consider three main arguments: land exploitation, socio-economic development, and ecological and environmental protection.
The hypothesis, research design and results are coherent and verifiable. As the authors point out, it is a matter of 'measurement' and not a more complex reflection on why or how such phenomena occur.
Even if the article is logical, the authors are invited to further understand land use, socio-economic development and ecological and environmental protection - as the definitions are narrow (only efficient to achieve a function) and the interrelationship has not been considered. Spatial governance strategies against urban sprawl are also something that needs further understanding - from the spatial and urban planning as well as the policy backgrounds.
Having said that, the article is consistent in itself and delivers what is promised in a justified way, with a sound methodology, using quantitative methods.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The topic, which is widely present in the international scientific literature, is explored in depth with adequate references and methodological systematicity, which allow for the return of a very clear framework of the state of the art and the context of reference. As a whole, the paper already appears sufficiently complete and structured, however, I do not find myself completely in agreement with the suggested dichotomy between urban sprawl and urban expansion based on the proposed indicators that, although effective, neglect the environmental issue and the assessment of impacts resulting from expansionary dynamics, which I believe are fundamental in judging effective or not urban development. This aspect, by the way, is stressed several times within the paper (see lines 45 to 48). In this regard, I believe that a strengthening of the arguments behind the choice of indicators, and excluding others, could better justify the premise of the paper.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
There is no doubt that distinguishing inefficient sprawl from effective expansion is very interesting and meaningful. And distinguish inefficient sprawl is difficult. This research is very valuable. The overall idea and logic of the paper is clear. However, I think the calculation of population, GDP and urban spatial expansion growth rate is wrong. Therefore, I am unable to comment on the scientific validity and reasonableness of the results of the manuscript. Comments for revision are as follows:
1. Line 28-30, the definition of urban agglomeration is inaccurate. Authors may characterize inefficient, disorderly, and low-density development mode as a characteristic of urban spatial expansion in urban agglomerations, but it cannot be a part of the definition of urban agglomeration.
2. In table 2, some literature citations are missing.
3. The methods and formulas for calculating the growth rates of population, GDP, and urban construction land are wrong. The authors calculated the value of the average annual growth, not the growth rate.
4. In Table 4, the authors summarize several inefficient urban sprawl patterns, but do not analyze them in depth in subsequent manuscripts, instead substituting inefficient urban spatial sprawl for specific urban sprawl patterns. I think it is more value in exploring specific urban sprawl patterns, especially to help come up with more targeted policy insights.
5. The conclusion section needs to be refined. The conclusions are not a collection of the results, but rather a further sublimation of the results to obtain universal conclusions.
Minor editing of English language required.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Dear Authors
Thank you for the hard work and the accomplishments
Best Regards
Reviewer 3 Report
The authors revised the paper in detail.
Minor editing of English language required.
