Urban Expansion Simulation Based on Various Driving Factors Using a Logistic Regression Model: Delhi as a Case Study

Round 1

Reviewer 1 Report

Paper Title: Urban Expansion Simulation Based on Various Driving Factors Using a Logistic Regression Model: Delhi as a Case Study

Comments

The current paper under review is an excellent piece of work given the rapid expansion of the Megacity of Delhi and resultant consequences on associated environmental components including water bodies, vegetation cover etc.

The paper has been able to present future direction of expansion and has scientifically/quantitatively projected the future development with a number of interlinked factors. Such paradigm of development in the populous developing cities of Asia is quite usual. But future expansion of cities with sustainability is extremely required. However, considering the immense efforts to address various driving forces, application of scientifically examined spatial technologies (RS/GIS and relevant statistical tools like logistic regression modelling etc.) and a very logically presented outcomes of the study, the paper can be accepted for publication. The outcomes of the paper are expected to contribute to guiding future expansion of Delhi in a right manner. The policy/decision makers should be immensely benefited from the results.

Finally, a review of English language to avoid redundancy in a couple places can be considered before final printing. The first figure showing the location of the study area in which study-area location is a bit confusing. Excellent piece of work! Please consider showing the location of the study area (in first figure) in a clear manner. 

Author Response

Reviewer 1

• a review of English language to avoid redundancy in a couple places can be considered before final printing.

The authors' response: The English language of the manuscript has been reviewed carefully.

• The first figure showing the location of the study area in which study-area location is a bit confusing. Excellent piece of work! Please consider showing the location of the study area (in first figure) in a clear manner. 

The authors' response: According to the reviewer's constructive comment, we have updated the location map of the study area (Fig 1). We have adjusted the contrast and brightness of the map in the GIS environment. In addition, we have added the names of the adjacent states and one extra map to make the location of Delhi NCT more precise. Please see fig.1 on page 3.

Reviewer 2 Report

The paper is an interesting proposal to identify the determinants of development of the urbanized zone of Delhi. It also proposes a tool to simulate further development. However, its structure contains some shortcomings. Moreover, some of the approaches used are not necessary for the objectives of the text. The following are mentioned as five important problems that need correction or supplementation:

1. The problem of references to literature on other cities. The selection of the described literature is rather random. It relates to different cities and requires a broader commentary pointing out the difficulties in comparing European, American, African, Indian and Chinese cities. All these areas of research are fundamentally different especially in terms of administrative and planning conditions. Perhaps a better solution would be a separate compilation of existing studies by certain geographical groups (types of countries, table?).
2. The problem of the study area. The authors relied on administrative division. The study is limited to the National Capital Territory (NTC) area. This approach causes loss of some information. The layout of the NTC boundaries is irregular. In some directions, the urbanized zone crosses them entering the neighboring states of Haryana and Uttar Pradesh. The problem is particularly related to the urban complexes of Ghaziabad, Faridabad and Gurgaon that connect to Delhi. The authors do not refer at all to the existence of these large centers, adjacent to the formal boundaries of Delhi. The article lacks explanation and justification for adopting such a criterion for delimitation of the study zone. 
3. the problem of nine factors. The research has derived nine factors that might affect urban expansion. The selection of these factors is based on the literature. However, there is a lack of both a better justification for this choice and a more detailed description of the selected variables. The problem especially concerns variables such as proximity to tourist sites (what are tourist sites, on what basis were they chosen?), proximity to restricted area (what is restricted area in Delhi?), proximity to medical facility (what medical facility was considered, hospitals or others?). The factor of proximity to medical facilities is particularly important because the regression study showed its importance for the directions of urban expansion. We should know if the study took into account only facilities already existing before the development of the built-up area. Perhaps some were created secondarily to serve new neighborhoods?
4. The problem of lack of references to spatial planning. Among the variables studied, none describing spatial planning was included. Certainly some areas around Delhi are developing in accordance with some planning documents and others are developing completely spontaneously. Perhaps a zero-one variable could be created to describe an area as being under or not under a spatial planning document? This factor may be crucial, and the proposed study omits it. If such information could not be obtained, the problem should somehow be described in the text. The current version of the article may suggest a complete lack of government control over the urban expansion process. Probably this control is not enough, but this aspect should not be omitted in the study. 
5.  The problem of division into sectors. It is not clear what role the division into 8 geographic directions of city development plays in the article. Of course, we learn about the geographical differentiation of development. However, it does not affect the objectives of the paper (determining factors and simulation). Perhaps this fragment can be removed, replacing it with a better characterization of 9 selected explanatory variables. Alternatively, direction could be an additional explanatory variable in the model?

Author Response

Reviewer 2

1. The problem of references to literature on other cities. The selection of the described literature is rather random. It relates to different cities and requires a broader commentary pointing out the difficulties in comparing European, American, African, Indian and Chinese cities. All these areas of research are fundamentally different especially in terms of administrative and planning conditions. Perhaps a better solution would be a separate compilation of existing studies by certain geographical groups (types of countries, table?).

The authors' response: The introduction section has been developed. The literature on other cities has been organized and classified by certain geographical groups in a table. Please see table 1 on page 2 and lines 50-65.

2. The problem of the study area. The authors relied on administrative division. The study is limited to the National Capital Territory (NTC) area. This approach causes loss of some information. The layout of the NTC boundaries is irregular. In some directions, the urbanized zone crosses them entering the neighboring states of Haryana and Uttar Pradesh. The problem is particularly related to the urban complexes of Ghaziabad, Faridabad and Gurgaon that connect to Delhi. The authors do not refer at all to the existence of these large centers, adjacent to the formal boundaries of Delhi. The article lacks explanation and justification for adopting such a criterion for delimitation of the study zone.

The authors' response:  The authors would like to appreciate the reviewer for the insightful comment regarding the query related to the adjoining neighbours of Delhi i.e., Ghaziabad, Faridabad, and Gurgaon.

The study has worked on the boundary of the National Capital Territory (NCT) of Deli because of 2 reasons:

1. Due to the dynamic change of the boundary of Delhi and the complexity of defining an accurate boundary for Delhi.
2. Due to the vast area of the National Capital Region (NCR) which includes the cities of Gurgaon, Faridabad, Noida, and Ghaziabad. It was very difficult to conduct full dedicated research in the whole NCR. Therefore, the study has focused on NCT (National Capital Territory) to investigate the urban expansion in this territory only.

However, according to the reviewer's comment, we have referred to this valuable point in 3 positions in the manuscript:

• Firstly, in section 3.2 (The trend of urban expansion in Delhi from 1989 to 2020) on page 10, lines 238~240.
• Secondly in section 3.5 (Limitations and Future Research) on pages 14 and 15, lines 343~348.
• Thirdly in the Conclusion section on page 1, lines 388-391

 

3. the problem of nine factors. The research has derived nine factors that might affect urban expansion. The selection of these factors is based on the literature. However, there is a lack of both a better justification for this choice and a more detailed description of the selected variables. The problem especially concerns variables such as proximity to tourist sites (what are tourist sites, on what basis were they chosen?), proximity to restricted area (what is restricted area in Delhi?), proximity to medical facility (what medical facility was considered, hospitals or others?). The factor of proximity to medical facilities is particularly important because the regression study showed its importance for the directions of urban expansion. We should know if the study took into account only facilities already existing before the development of the built-up area. Perhaps some were created secondarily to serve new neighborhoods?

The authors' response:  First of all, the authors want to clarify that twelve indicators have been derived from previous literature but due to lack of data, two factors were excluded which are economic activities and urban master plans. later, another factor (the slope factor) has been excluded from the model for optimum model fitting. The following paragraph has been added to the methodology section on page 4, lines 152~157 to explain this point.

Regarding tourism sites, restricted areas, and proximity to medical sites, the clarification as follows:

> The tourist sites were defined based on the most popular tourist destinations in NCT Delhi according to the official Tourism website for the government of NCT of Delhi. These sites including Lotus Temple, India Gate, Parliament House, Purana Quila, Qutab Minar, Rashtrapati Bhavan, Humayuns Tomb, Safdarjung Tomb, Neheru Park, Raj Ghat. The clarification of this variable has been done on page 5, line 159.

 

> The restricted area in Delhi is the Indira Gandhi International Airport zone (the clarification of this variable has been done on page 5, line 159.) which was defined as a restricted area by the government of NCT of Delhi. “ No building shall be built or erected, nor may any tree be planted or grown on any ground within a twenty-kilometers radius of the civil and defense aerodromes' Reference Points, as defined in Schedule III to Schedule VII”. In addition, the No Objection Certificate must also be issued for level roadways and level railway lines within one kilometer of the airport perimeter wall. Therefore, the airport is considered as a restricted zone for urban development. It is worth noting, the airport zone has been considered as a restricted area for urban expansion in plenty of previous articles such as:

-Tripathy, P., & Kumar, A. (2019). Monitoring and modelling spatio-temporal urban growth of Delhi using Cellular Automata and geoinformatics. Cities, 90, 52-63.

-Jafari, M., Majedi, H., Monavari, S. M., Alesheikh, A. A., &KheirkhahZarkesh, M. (2016). Dynamic simulation of urban expansion based on cellular automata and logistic regression model: Case study of the Hyrcanian Region of Iran. Sustainability, 8(8), 810.

-MOHAMED, B., Fatiha, B., Hassan, R., SAID, B., TAOUFIK, B., NAJAT, B., & Mohamed, B. (2020). Modeling of Urban Growth Using Cellular Automata and GIS Case of Benslimane in Morocco.

> The variable of proximity to medical facilities. This variable includes both general government hospitals and private hospitals. These facilities were already existing in the base year of 1989. The clarification of this variable has been done on page 5, line 160.

 

4. The problem of lack of references to spatial planning. Among the variables studied, none describing spatial planning was included. Certainly, some areas around Delhi are developing in accordance with some planning documents and others are developing completely spontaneously. Perhaps a zero-one variable could be created to describe an area as being under or not under a spatial planning document? This factor may be crucial, and the proposed study omits it. If such information could not be obtained, the problem should somehow be described in the text. The current version of the article may suggest a complete lack of government control over the urban expansion process. Probably this control is not enough, but this aspect should not be omitted in the study.

The authors' response:  The study did not investigate this factor due to difficulty of obtaining the required data and we have referred to that in the Methodology section on page 4 “two factors (economic activities and urban master plans) were excluded from the study due to lack of data in the study area” and in the Discussion section on Page 15 (3.5 Limitations and Future Research), lines 340~342. 

The problem of division into sectors. It is not clear what role the division into 8 geographic directions of city development plays in the article. Of course, we learn about the geographical differentiation of development. However, it does not affect the objectives of the paper (determining factors and simulation). Perhaps this fragment can be removed, replacing it with a better characterization of 9 selected explanatory variables. Alternatively, direction could be an additional explanatory variable in the model?

The objective of this research is not only limited to urban expansion simulation, rather gives a better visualization in terms of directional analysis of urban expansion. The eight geographic divisions were utilized to visualize the trend of urban expansion in Delhi from 1989 to 2020. In addition to showing the change of built-up area at different distances. As each division reveals the pattern of urban expansion which is significant for local authorities and decision-makers. On the other hand, the study did not employ characterization of 9 selected explanatory variables or the direction of expansion as variables in the model, because the authors believe that utilizing them in visualizing urban expansion is more useful for the study.   

 

 

Reviewer 3 Report

Manuscript Number: Sustainability-1353243

Title: Urban Expansion Simulation Based on Various Driving Factors Using a Logistic Regression Model: Delhi as a Case Study.

Comments:

The manuscript has chosen a significant subject representing Delhi’s massive urban expansion resulted in habitat fragmentation, deforestation, and difficulties in running urban utility services effectively in the new extensions. The result of this research may be helpful for local authorities to recognize the patterns of future expansion.

Some of my observations, which can be corrected/incorporated in MS, are as under:

The abstract is not perfectly representing what exactly the manuscript is all about. The authors should modify and clearly state in the abstract in the contribution.

The authors should highlight the innovation of their work as so many researchers already worked on the same applications in different directions.

It is not clear what data have been used for the validation. The authors should clearly explain in the manuscript.

I could not understand why the authors did not use any Fuzzy ANN, Fuzzy C mean clustering or Fuzzy with Deep Learning and so many other recent approaches that are most adaptive in use.

There have been some essential papers written in the past few years on this issue. Authors can be incorporated as citations also.

The current research should focus on a novel approach for further studies in these areas, not existing ones.

Author Response

Reviewer 3

• The abstract is not perfectly representing what exactly the manuscript is all about. The authors should modify and clearly state in the abstract in the contribution.

The abstract has been updated and revised according to this valuable comment. Please see page 1, lines 15~30.

• The authors should highlight the innovation of their work as so many researchers already worked on the same applications in different directions.

The innovation of the work has been highlighted in the introduction and Conclusion sections. Please see page 3, lines 89~96, and page 15 lines 365~367.

• It is not clear what data have been used for the validation. The authors should clearly explain in the manuscript.

The authors have added more details about the data used for the validation in the manuscript, please see page 14, lines 327~332.

• I could not understand why the authors did not use any Fuzzy ANN, Fuzzy C means clustering or Fuzzy with Deep Learning and so many other recent approaches that are most adaptive in use.

The recent approaches mentioned have been discussed in the Introduction, and Limitations and Future Research sections, please see page 2, lines 75~84, and page 14, lines 357-363.  

• There have been some essential papers written in the past few years on this issue. Authors can be incorporated as citations also.

The references have been updated. A set of essential papers have been added, please see the reference section on pages 16~19.

 

• The current research should focus on a novel approach for further studies in these areas, not existing ones.

The study has suggested a novel approach for further studies by combining other models like artificial intelligence-based models and the CA model for further studies, as discussed in Section 3.5 Limitations and Future Research, please see pages 14 and 15 lines 349-363.

Finally, the revised manuscript has been undergone extensive English revisions by MDPI English Editing Services.

Round 2

Reviewer 2 Report

Most of the comments from the review were fulfilled by the authors of the article. The literature description has been completed and structured. The justification of the adopted research area is also more complete, as well as a better description of the determinants of urban expansion. 
As a reviewer, I still believe that the section on geographical sectors does not contribute to the objectives of the article. It could be removed from the text. A decision on this must be taken by the editors together with the authors.
The problem that I consider unresolved remains the lack of reference to spatial planning. The authors explain that this was the underlying assumption of the study. They postulate separate future studies in this area. However, the absence of planning in the described factors shaping the spatial development of Delhi seems to be a mistake. Even if we drop the inclusion of this factor in the model, it should still be presented descriptively as one of the soft determinants.

 

Author Response

Dear respected reviewer,

Kindly find our responses to your valuable comments:

• As a reviewer, I still believe that the section on geographical sectors does not contribute to the objectives of the article. It could be removed from the text. A decision on this must be taken by the editors together with the authors.

The authors' response: First, we would like to thank the reviewer for his/her valuable comment. The authors believe that the analysis of urban expansion on geographical sectors is useful for our study for these reasons:

1. The eight geographic sectors were utilized to visualize the trend of urban expansion in each sector in Delhi from 1989 to 2020 which is significant for local authorities.
2. These sectors show the change in the built-up area at different distances. Thus, identifying the nature of the relationship between urban expansion and the distance from the center of Delhi.
3. This analysis helped in recognizing spatiotemporal patterns in each zone which are useful decision-makers.

It is worth noting, the analysis of urban expansion on geographical sectors has been applied in plenty of previous articles related to urban expansion such as:

- Wu, S.; Sumari, N.S.; Dong, T.; Xu, G.; Liu, Y. Characterizing urban expansion combining concentric-ring and grid-based analysis for latin american cities. Land 2021, 10. 10.3390/land10050444.

- Nkeki, F.N. Spatio-temporal analysis of land use transition and urban growth characterization in Benin metropolitan region, Nigeria. Remote Sens. Appl. Soc. Environ. 2016, 4, 119–137.

- Ramachandra, T. V.; Bharath, A.H.; Sowmyashree, M. V. Monitoring urbanization and its implications in a mega city from space: Spatiotemporal patterns and its indicators. J. Environ. Manage. 2015, 148, 67–81. 10.1016/J.JENVMAN.2014.02.015.

• The problem that I consider unresolved remains the lack of reference to spatial planning. The authors explain that this was the underlying assumption of the study. They postulate separate future studies in this area. However, the absence of planning in the described factors shaping the spatial development of Delhi seems to be a mistake. Even if we drop the inclusion of this factor in the model, it should still be presented descriptively as one of the soft determinants.

The authors' response:  The authors would like to appreciate the reviewer for his/her important comment. We have added a new section (3.5 Lack of spatial planning in Delhi) for discussing this crucial factor. Please see pages 10 and 11 lines 250~260.

Finally, the revised manuscript has been undergone extensive English revisions by MDPI English Editing Services.

Reviewer 3 Report

MS now improved.

Author Response

Thank you for your valuable comments which helped in developing the manuscript.