Urban Flood Vulnerability Assessment in Freetown, Sierra Leone: AHP Approach

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Editor-in-Chief
hydrology-3162225
Manuscript Title: FLOOD VULNERABILITY ASSESSMENT USING ANALYTIC HIERARCHY PROCESS (AHP) UNDER THE IMPACTS OF RAINFALL AND LAND USE CHANGE OVER TWO DECADES (2001-2020) IN FREETOWN, SIERRA LEONE

Through a comprehensive evaluation of the work, here is my feedbacks on the different parts of the paper. The main shortcoming of the presented work is that, the use of the common and outdated AHP method in recent works cannot be accepted as a novel research topic. Stringing the applications of the finding/presented work would improve the text significantly.
Here are my comments on the shortcomings of the manuscript, which cab be considered through a major revision.

Abstract and Title:
-The title is too long and need a shortening, e.g., avoid mentioning the AHP in the title.
- Present some key numerical results in the abstract.
- Use the keywords other than used in the title.
Introduction:
- Provide more research background regarding the different dimensions of flood vulnerability index, with extra explanations considering different factors, various impacts, and practical applications.
- Add much more international literature to be of interest for diverse spectrum of readers.
- Explain about different dynamic driving force agents that intensified flood vulnerability including climatic, human, and natural agents, in the introduction part.
- I strongly recommend adding a part titled “Literature Review”, which cover different previously conducted research through all over the world.
- Before mentioning the objective of the study, make a summary based on the previous works to highlight the meaningful perspectives of your research.
- Mentioning the novelty of the research is missing, that can be stated in a closing paragraph emphasizing on the uniqueness of the current research.
- The text does not provide any metrical regarding the following statement as an objective:
“Ultimately, this research endeavors to contribute towards the overarching goal of fostering resilience and sustainability in the face of escalating flood risks within urban environments, epitomizing a crucial step towards safeguarding the well-being of Freetown's populace and its urban infrastructure.”

Study area:
- It would be helpful to provide some descriptions regarding the precipitation amount, dominant climate characteristics, temperature fluctuations, and the main land use type/s in the upstream watershed of the study area.
Research Methodology:
- Adding details such as spatial resolution (scale of the maps) and the year for the land use maps to Table 1 would greatly help for the interested readers regarding the availability of the data to implement the current research in their own area.
- Lines 115 to 126: should be supported by appropriate references. This shortcoming is also existed in the whole research methodology section.
- Lines 103 to 166: need to be classified with appropriate headings. Also, it is recommended to explain each index presented in the research metho section separately.

Results and discussion:
- It is better to include numbers in Figure 3 (Legend I mean).
- According to a wide range of publications, it is obvious that the hourly or heavy daily storm events/rainfalls generate floods (According to me, the max-24-hr rainfall is accessible in every area), therefore it is not so logical to use annual average values as a factor in flooding studies and flood vulnerability assessment). Using max-24-hr rainfall would be calculated in different return intervals/period, that strongly will improve the results confidence in assessing FV. Provide extra explanations and mention these limitations in the text supported by appropriate findings in the researches with similar approach implemented in the current research.

Conclusions:
- Since the management factors has not been considered in the analysis, therefore, the following sentence does not make sense. As the text referred to the destructions of the natural land use categories and increased the intensity of flooding). Therefore, re-writing this part can help in resolving the ambiguity.
“The flood vulnerability maps from 2001 to 2020 depict a gradual shift from high to medium vulnerability, particularly in the Western Area Rural. This trend suggests improvements in land management and infrastructure, reflecting broader regional adaptations to changing climatic conditions (58).”
- Mentioning the limitation/source of errors and assumptions of the findings and implemented approach should be provided.
- In the present study, the vulnerability of elements at risk of flooding is not taken into account. Therefore, include extra explanations for the readers.
- How and how much you trust the results, as the recorded flood data and river flow statistics were not employed in determining the accuracy of the results, validation of prepared flood hazard maps.
- What is the return period/recurrence interval of the prepared flooding vulnerability?

Comments on the Quality of English Language

The English proficiency of the manuscript is satisfactory, but minor revisions are required.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This study assesses flood vulnerability in Freetown, Sierra Leone, from 2001 to 2020 using the Analytic Hierarchy Process (AHP) integrated with various indicators like rainfall and land use change. The authors identified rainfall (with the highest weight of 0.27) as the main flood-inducing factor and observed a shift in high-vulnerability zones from widespread areas in 2001 to concentrated zones in the east and southeast by 2020. This study may provide insights for policymakers in flood hazard mitigation and urban planning.

This study is of interest to the journal readership. However, some key points need to be addressed before publication. I hope that my comments help in preparing an improved paper. I believe this manuscript is valuable and might deserve publication after the comments are addressed.

1.      The paper needs to provide more methodological details to allow the readership to repeat their work in this or other study cases. These include, but are not limited to, how exactly were the FV indicators weighted (L83-84) – section 2.4.1 is vague and does not allow repeatability of what was done in this paper. Similarly, the meaning of the consistency ratio is confusing, and the choice of 0.10 as the threshold for assessment seems arbitrary (is it related to statistical significance?). Thus, details of the methodology should be carefully clarified.

2.      The authors conclude that rainfall was the criterion with the highest priority in the flood vulnerability assessment. Yet, they seem to have used annual rainfall (L141-143, L245, and Fig. 3) instead of extreme rainfall, which would drive floods in general. I recommend that the authors use conventional annual maxima (or another extreme-event dataset) as input data.

3.      A factor omitted is climate change impacts - a warming atmosphere can increase its capacity to hold moisture and thus may lead to increasing extreme rainfall (Kharin et al., 2013; Trenberth, 2011). Climate change impacts on hydrological extremes can be addressed through nonstationary approaches. For example, there are easy-to-use systematic, software-supported, and practice-oriented frameworks for frequency analysis that can account for nonstationarity and integrate recent advancements in nonstationary analysis (e.g., Vidrio-Sahagún et al., 2024).

4.      The literature review could be more robust. The state-of-the-art and relevant literature on flood vulnerability assessment and the AHP should be included in the introduction to provide a big picture of the matter and highlight this paper's contribution.

5.      The writing could be substantially improved. For example, several typos must be corrected (e.g., L184, L39, etc). Be more specific on what “erratic rainfall patterns” (L44) exactly mean. Besides, Tables 1 and 2 and Figures 1 and 2 should be mentioned and described with enough detail in the manuscript.

 

References

Kharin, V. V., Zwiers, F. W., Zhang, X., and Wehner, M. (2013). Changes in temperature and precipitation extremes in the CMIP5 ensemble. Climatic Change, 119(2), 345–357. https://doi.org/10.1007/s10584-013-0705-8

Trenberth, K. E. (2011). Changes in precipitation with climate change. Climate Research, 47(1–2), 123–138. https://doi.org/10.3354/cr00953

 

Vidrio-Sahagún, C. T., Ruschkowski, J., He, J., and Pietroniro, A. (2024). A practice-oriented framework for stationary and nonstationary flood frequency analysis. Environmental Modelling & Software, 173, 105940. https://doi.org/10.1016/j.envsoft.2024.105940  

Comments on the Quality of English Language

Please refer to the 5th comment of my review.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This research work is on a topic of relevance and general interest to the readers of the journal. In the light of the above, there are no specific grounds for opposing the publication of this research work but some revisions are for sure needed to improve its readability. The title is quite clear, but I would suggest shorten it in order to be more effective.

I would suggest extending the introduction to better contextualize the work within the existing literature and to more effectively highlight its novel contributions. In this regard, it could be beneficial to frame the issue of flooding within a broader context. For example, why not cite other instances globally where similar challenges related to urban planning and climate issues arise? (give a look at https://doi.org/10.1016/j.scs.2023.104856 and https://doi.org/10.1016/j.heliyon.2023.e12955).

I suggest the authors to provide a few additional details regarding the climate in the study area. However, aside from that, the materials and methods section appears to be excellent in terms of organization and content. In the results section, I would encourage the authors to more clearly articulate the correlation between the analyzed indicators and the flooding phenomenon.

Overall, this is a significant research work whose "novelty" should be better articulated and expressed.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Hello,

Dear Editor-in-Chief

The authors have responded to the comments and majority of suggestion/comments have been addressed in the text. Therefore, the paper has been greatly improved and is acceptable for publication.

Final Reviepwer

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The authors did not adequately address my comments in their response. I believe this manuscript should not be published until it undergoes another round of proper peer review:

1. They did not include my full comments in their response; instead, they selectively omitted parts at their discretion. Why should we bother to provide feedback if it is ignored?

2. They failed to indicate where changes were made to address my comments clearly. I strongly recommend that they specify the line numbers where revisions were implemented (that's why they exist in the peer-review process). We, the reviewers, cannot spend time figuring out where the changes are.

3. They claimed to have made changes that are, in fact, missing from the manuscript. For instance, the discussion on climate change and nonstationarity mentioned in their response was not added to the manuscript. This highlights the importance of addressing comment #2.

A proper point-by-point response to the first round of peer review comments is required.

Comments on the Quality of English Language

The quality of the English language is appropriate.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 3

Reviewer 2 Report

Comments and Suggestions for Authors

This paper can now be processed for publication