Assessing Economic Vulnerability from Urban Flooding: A Case Study of Catu, a Commerce-Based City in Brazil

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper presents a robust and integrated methodology to assess urban flood risk and its economic impacts on a vulnerable population in Catu, Brazil. The study successfully combines hydrological/hydraulic modeling (HEC-HMS, HEC-RAS) with socioeconomic analysis, filling a critical gap in the literature for data-scarce environments. The findings are significant for local urban planning and risk management, clearly demonstrating how floods exacerbate social inequality. The manuscript is generally well-written, but certain sections require clarification, and the economic loss model, while innovative, needs a more thorough justification.

Keywords: Consider adding more specific keywords like "hydraulic modeling," "HEC-RAS," "socioeconomic vulnerability, "informal economy," and "climate change adaptation" to improve discoverability.

The final paragraph outlining the methodology is quite detailed and might be better suited for the Materials and Methods section. Consider shortening it in the introduction to maintain a high-level overview.

Equation Numbering: There are two "Equation 03"s (one for Time of Concentration and one for Economic Loss). This must be corrected for clarity.

Can authors provide a quantitative or documented rationale—such as a correlation between simulated flood depth/duration and observed recovery times from historical events, or a clear set of decision rules—for how the specific 'Days of Interruption' values (4, 7, 10, 20) were assigned to each return period, rather than relying on expert estimation?
Ensure all figures are included and referenced correctly in the final manuscript.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The article “Assessing Economic Vulnerability from Urban Flooding: A Case Study of Catu, a Commerce-Based City in Brazil” investigates how extreme rainfall events affect the economy of the municipality of Catu (Bahia), with emphasis on the informal sector (street vendors and local merchants). The main objective is to model urban flood scenarios with different return periods (10, 25, 50, and 100 years) and estimate economic losses. In summary, the article presents good integration between hydrological modeling and socioeconomic analysis, highlighting the vulnerability of populations dependent on informal commerce in the face of urban floods and climate change.

However, the manuscript in its current form requires several adjustments regarding clarity and presentation of the methodology and results.

 

Introduction:

To give more emphasis to the justification of the study, I recommend inserting in the introduction the historical record of extreme events in the municipality of Catu and the impacts caused by these events (social, environmental, economic...).

The last four paragraphs of the introduction (lines 77 to 94) describe the methodology used to achieve the objective. I recommend ending the introduction with a paragraph describing the objective of the study and removing the methodological part from the introduction.

To make the introduction more robust, aligned, and justifiable according to the purpose of the work, it would be interesting to discuss the advantages of using hydrological and hydraulic models applied to extreme event studies. Examples of works and models already used for this purpose would help justify the choice of the HEC model, and also highlight the advantages and benefits of such analyses for the population, the scientific community, and managers. In addition, it is necessary to emphasize the importance of the economic analysis (what are the benefits, advantages, impacts?).

 

Materials and Methods:

The materials and methods section needs to be restructured. There is repeated information in different subsections. The authors could condense the information and merge topics. Presenting a flowchart would help readers better understand the methodological phases and processes and would also help the authors restructure the topics and information.

Do street vendors occupy the area that would be flooded in the event of an inundation? If so, this must be made clear in the text, either in the methodology or the introduction.

Figure 1 presents the digital elevation model. It is necessary to present this in the caption as well, so that altitude interpretation is possible.

In Figure 2, it is necessary to clearly indicate where the urban area of Catu is located.

Section 3 – “Materials” mentions the databases used (https://search.asf.alaska.edu; https://brasil.mapbiomas.org/; https://www.hec.usace.army.mil/software/hec-hms/downloads.aspx; https://portal.inmet.gov.br/; https://cidades.ibge.gov.br/brasil/ba/catu/panorama; https://datampe.sebrae.com.br/explore?report=Geography&variant=All; https://infosanbas.org.br/). In most cases, the links are provided in the text and in some cases the access date. It is necessary to mention these databases as references and provide the links in the reference list. The only database cited is MAPBIOMAS, and its reference is presented incorrectly in the list. If you wish to keep the links in the text, I recommend inserting a table with database/variable used, citation, and link.

Specify the spatial resolution of the DTM (line 148).

I recommend removing the information on population (lines 175–177). The information on the number of inhabitants of Catu was already presented earlier in the text.

The title of Table 1 needs correction.

Table 1 needs to be formatted and presented with a standardized font. In addition, the unit of area (km²) must be adjusted.

Remove “However” from line 183.

Figure 5 needs to be adjusted. The legend shows an item in blue (water surplus) that does not appear in the image.

Were the parameters presented in Table 2 obtained from the DTM? If so, this must be made clear in the text.

Table 2 presents three sub-basins. It would be useful to identify the three sub-basins in an image in the materials and methods section.

The main variable for constructing hyetographs and hydrographs is precipitation. The authors mention using INMET data, but do not present how many and which climate stations were used, nor the period of the historical series used for the analyses. This information is important to ensure reproducibility of the study.

The authors present Figure 4 (1991 to 2001 – 11 years) and Figure 5 (1991 to 2020 – 30 years). Shouldn’t these cover the same period?

How was the LMI obtained? Line 349.

 

Results and Discussion:

Remove “This table presente” from the title of Table 5.

Figure 13 shows the loss related to the number of interruption days. As it is a straight line increasing proportionally with the number of interruption days, this figure could be removed from the study, since this can be understood from the information already presented in the paragraph above the figure (line 492).

It would be useful to explain in more detail the validation of the hydrological model with the available data (even indirect), including a discussion of uncertainties.

The economic model is simplified (it only considers interruption days) and may underestimate associated costs (infrastructure, cleaning, physical damages). This needs to be better addressed in the discussion.

The discussion could be more critical by comparing the results with other studies on urban economic vulnerability in Brazil and in international contexts. Such comparison would help position the scientific contribution more clearly.

The authors state that Figures 15, 16, and 17 were adapted; however, they were taken from the study by Slater et al., 2021 (https://doi.org/10.1029/2020GL091824).

The discussion on climate change is not well grounded in the study. The authors rely heavily on external references to justify possible changes in rainfall patterns and return periods but do not present their own analyses of the local or regional historical series. This weakens the argument about the impact of climate change in Catu.

It is not clear how climate change was addressed in the study. The period of the historical series used to assess rainfall patterns is not presented or not clear. It is recommended to clearly state the temporal extent of the data analyzed (e.g., 1980–2020) and justify its adequacy. The authors cite studies that show increases or decreases in future flows, but it would be more consistent to include at least an exploratory analysis with local/regional data (annual precipitation trend, extreme intensity, variation of indices such as SPI or Rx5day). In addition, the flood history would be fundamental, i.e., include a brief systematization of past events in Catu or in the Catu River basin, with reference to recorded disasters (last 10, 25, 50, and 100 years, if available). This would provide greater empirical support for the simulations. It is also recommended that the authors make it clear whether the future scenarios presented are merely generic projections from global/regional studies or whether they reflect observed data in the area. This must be well defined so as not to generate misinterpretations.

 

References:

It is necessary to review the reference list. Some references are incorrectly presented, especially those that are online databases and require the inclusion of links.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript submitted for review, entitled Assessing Economic Vulnerability from Urban Flooding: A Case Study of Catu, a Commerce-Based City in Brazil, is of the type: article.

 

The article concerns the hydrodynamic modeling of urban catchments using the HEC-RAS and HEC-HMS programs, as well as the integration of the obtained results for critical urban flood events with socio-economic losses.

The current form of the article indicates that it lies somewhere between a project report and a research article. My comments are aimed at clarifying the existing inconsistencies and guiding the paper more towards the form of a research paper."

 

Abstract:
The abstract introduces the reader to the issue of urban flooding and identifies problems occurring in the city of Catu. It refers to challenges related to urban floods and changes in the characteristics of critical rainfall events; however, it omits the human factor in this context—namely, improper urbanization.
The authors correctly presented the applied research tools and methods, such as HEC-HMS, HEC-RAS, and regression analysis. However, they did not clearly define the research objective that would indicate the paper.

Comments:

• Line 12: The word “losses” should be reconsidered; the sentence requires rephrasing.
• The abstract lacks a clear statement of the research objective.
• If the aim of the study was to develop a hydrodynamic model of the Catu catchment and analyze rainfall events, it suggests the work is more of a technical report rather than a research paper. It is recommended that the authors explicitly formulate the research aim they intended to achieve.
• The abstract does not include specific results of the conducted research.

 

Keywords:
I would suggest adding hydraulic or hydrodynamic modeling (depending on which simulation parameters were considered).

At the same time, the keywords include an economic model, which was not mentioned in the abstract. If an economic model was indeed part of the study, this also affects the research objective and how it should be formulated.

 

 

Introduction:
The introduction addresses the issue of urban flooding caused by natural hazards and briefly refers to problems in the city of Catu. The literature review focuses on flood issues, including urban floods, global fatalities, and economic losses in Brazil.

Comments:

• Line 47 – “unplanned urban growth”: This term may be inaccurate. I suspect the authors intended to refer to improper urban planning; if not, this should be clarified.
• Lines 46–48: It would be advisable to include references to relevant literature here.
• Line 50: The introduction lacks a concise overview of adaptation measures for urban catchments in response to the presented problems. For example, it could mention:
• Digital upgrades of drainage and detention devices for forced retention,
• Nature-based solutions (NbS),
• Classic retention solutions, e.g., assessment of forced retention efficiency in stormwater drainage systems.
• Lines 47–50: The gap in the literature is correctly introduced, but it should be expanded. The authors focused mainly on urban hydrology. If they claim the research gap concerns socio-economic impacts of urban floods on low-income populations, the introduction should at least briefly acknowledge this problem. At this stage, the introduction does not clearly direct the reader to the stated research gap.
• My comments are not critical of the work itself, which I find appropriate, but rather address the presentation. In the introduction, the reader should receive a clear statement of the study aim. For example (if I understood correctly), the study integrates hydrodynamic simulations of urban catchments for extreme events with an assessment of socio-economic losses, which allows answering specific questions or demonstrating certain findings. A clear statement of the novelty intended by the authors is needed.
• Lines 56–58: This is a very valuable observation that goes beyond the case study. Such information should also appear in the abstract (e.g., if the authors developed a specific algorithm or procedure for assessment).
• Lines 61–61: Another stated objective or its semantic equivalent:

“the scientific understanding of the complex interaction between natural phenomena, urbanization, and social inequality”
This is well formulated; however, I suggest that the authors harmonize and specify the scientific objective, particularly between the abstract and introduction.

• Lines 62–64: Another statement of the research objective, which is concise:

“analyze the relationship between extreme rainfall events and the socioeconomic impacts in the region of the Municipal Supply Center in Catu”

• Lines 69–82: This is a methodology description and should not be included in the introduction; it belongs in the dedicated methodology section.
• Lines 83–87: The main results should be concisely presented, ideally also in the abstract.

Overall analysis of the abstract and introduction indicates that the study includes:

1. Development of a hydrodynamic model of the Catu catchment and rainfall analysis.
2. Identification of the research gap: socio-economic impacts of urban floods on low-income populations.
3. Integration of hydrodynamic simulations of urban catchments for extreme events with socio-economic loss assessment.
4. A replicable framework applicable in other regions facing similar challenges.
5. Analysis of the relationship between extreme rainfall events and socio-economic impacts in the Catu Municipal Supply Center.

Conclusion:
Based on the introduction, it remains unclear what the authors’ specific objective is, as the presentation does not clearly unify the research gap, methodology, and study aim.

 

 

 

Materials and Methods (Review Comments)

Materials and Methods:
In this section, the authors appropriately describe the study case of the municipality of Catu from the perspective of subsequent hydraulic analyses. At the same time, a detailed presentation of economic data is provided for social analyses. Overall, the methodology is described in great detail.

Main comments:

• The section should separate the results from the actual methodology. Sections 3 and 4 should ideally be treated as subsections of Materials and Methods.

Specific comments:

• Lines 147–351: Consider moving this content to Section 3.
• Lines 148–176: Hyperlinks should be replaced with formal literature citations.
• Line 155: The software used is popular; therefore, it is unnecessary to indicate the download source. For example, the authors do not specify where QGIS was obtained. It is sufficient to mention which software tools were selected. There is also a lack of clarification regarding the scope of HEC-RAS usage.
• Lines 230–232: Please verify all manuscript variables (e.g., Tr, t, K), which should be written in italic.
• Lines 233–236: A proper equation for multiple regression should be included according to the literature. Additionally, a sentence should state that the developed model was calibrated (as inferred from the manuscript), which is crucial for readers.
• Lines 238–240: These lines present results, so they should not be included in the methodology section.
• Overall, the section should separate obtained results from the actual methodological description.
• Figure 6: The term “annos” appears; this should likely be “annual”.

 

Results and Discussions

Results:
The results are presented in detail. My main concern regards the developed regression equations: the authors focused on using linear regression, but they do not demonstrate that their model adequately explains the dependent variables.

Specific comments:

• Figure 8: The caption should be concise; the description should be provided in the text.
• Lines 365–366: This statement does not seem supported by the data presented in Table 4. The presence of linear relationships can only be confirmed after a detailed analysis of the data, e.g., using RESET tests. The data in Table 4 do not convincingly indicate a linear relationship.
• Lines 375–377: This content should be moved to the methodology section.
• Lines 450–468: It is unclear whether the developed regression model is truly linear and adequately explains the dependent variable. It seems that this has not been demonstrated.
• Figure 12: In the text, the figure should be described clearly, specifying what the shaded pink area represents.

 

The manuscript currently lacks a dedicated discussion section. The following points should be addressed:

1. Discussion of the obtained results in the context of previous studies on similar topics.
2. Limitations of the current model and the study.
3. Future research perspectives and potential improvements.

 

 

 

Conclusions

Lines 651–665:
The summary mainly presents general conclusions focused on the case study, without providing broader, generalizable insights. After reading the abstract, this section gives the impression of a project report rather than a research article. In the text, the authors also mention the development of a procedure integrating hydrodynamic modeling with socio-economic impacts. I suggest focusing on this aspect so that the results obtained could be applied beyond the Catu area.

In the conclusions, the authors partially engage in discussion, which makes it more difficult for the reader to follow the manuscript. I recommend splitting the conclusions, separating:

1. Specific results obtained from the developed integration procedure, and
2. Concrete results from the conducted analyses.

I would like to congratulate the authors on addressing a comprehensive topic that requires considerable time and effort to develop an appropriate model. At the same time, I emphasize that my comments aim to enhance the scientific value of the work.

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

i have no more suggestions and recommend accept. Congratulations

Author Response

Thank You

Reviewer 2 Report

Comments and Suggestions for Authors

The authors addressed all concerns satisfactorily.

Author Response

Thank You

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have partially addressed the previous reviewer’s comments; however, the fundamental issues remain unresolved, and the provided responses are not adequate. The particularly important but unaddressed comments (from the previous review) include points: 12, 13, 14, 19, 24, and 25. Of particular concern is the inference of a linear relationship based solely on the values of R², r, and RMSE.

After revision, the manuscript remains largely focused on the hydrodynamic modeling of urban catchments (most of the conclusions relate to this topic). Furthermore, some conclusions refer to issues not supported by the conducted research, such as statements regarding credit-related aspects – these conclusions were drawn without performing any financial analysis.

The core part of the study consists of hydrodynamic modeling conducted for a specific location. However, the application of the adopted method has not been presented clearly enough. It would be more appropriate to define this element as a procedure that includes, among others, a description of the applied algorithm and the underlying assumptions.

My overall evaluation of the manuscript remains the same as before. I again suggest that the authors focus more on presenting the proposed methodology, supplementing it with a corresponding algorithm (e.g., in graphical form), and revising the conclusions to ensure they are concise, directly derived from the conducted research, and provide a genuine contribution to the advancement of the field.

Author Response

Comments: 

The authors partially addressed the comments of the previous reviewer; however, the fundamental issues remain unresolved, and the responses provided are inadequate. Particularly important, unaddressed comments (from the previous review) include points 12, 13, 14, 19, 24, and 25. Of particular concern is the inference of a linear relationship based solely on the values of R² r, and RMSE.

Response: 

We sincerely appreciate your thorough and critical analysis of the revised manuscript. Your comments have been fundamental in enhancing the scientific rigor and focus of our research. We acknowledge the validity of your concerns and confirm that the manuscript has undergone substantial revision and restructuring in direct response to your feedback, ensuring that the fundamental issues are now fully addressed. It is important to emphasize that the other reviewers (Reviewer 1 and Reviewer 2) have accepted all corrections and the manuscript in its current format.

Comments: The authors partially addressed the comments of the previous reviewer; however, the fundamental issues remain unresolved, and the responses provided are inadequate. Particularly important, unaddressed comments (from the previous review) include points 12, 13, 14, 19, 24, and 25.

We regret that the previous changes were not deemed satisfactory. In the current review cycle, we conducted a point-by-point review of all original comments, including points 12, 13, 14, 19, 24, and 25, ensuring each was completely addressed.

We must stress that, due to the substantial revision and complete restructuring of the manuscript, the original numbering of these points has been altered, making it impossible to strictly identify the location of the issues pointed out solely by their number. Nevertheless, the concept underlying each of these comments has been understood, incorporated, and corrected in the new manuscript version.

Comment: Of particular concern is the inference of a linear relationship based solely on the values of R², r, and RMSE.

We acknowledge that inferring a linear relationship for a complex physical process based solely on statistical coefficients is, indeed, scientifically inadequate. Our intention in employing these metrics was to demonstrate the high predictive correlation of the developed Vulnerability Function, and not to assert the intrinsic linearity of the hydrodynamic processes.

Justification and Adequacy of Metrics:

The Coefficient of Determination (R²), the Correlation Coefficient (r), and the Root Mean Square Error (RMSE) are widely accepted and sufficient statistical metrics within the scientific community for the purpose they serve in this project: the validation of the predictive capacity of an empirical loss model.

The R² and r are used to validate the coupling between the modeled water depth and the real economic losses (obtained from field research), confirming that the Socioeconomic Vulnerability Function possesses a high capacity for prediction and statistical validation to estimate the impact of floods in the study area.

The RMSE quantifies the precision of our loss model in the relevant monetary units.

Thus, the presented values (e.g. R² = 0.98$) prove the performance and robustness of our Vulnerability model (Depth-Damage Function) in predicting losses, and not the physical nature of the relationship.

Comments: After revision, the manuscript remains largely focused on the hydrodynamic modeling of urban catchments (most conclusions relate to this topic). Furthermore, some conclusions refer to issues not substantiated by the research conducted, such as claims about credit-related aspects – these conclusions were drawn without performing any financial analysis.

Response:

We recognize the reviewer's observation regarding the apparent focus on modeling. However, the manuscript was structured to demonstrate that hydrodynamic modeling is the essential means to achieve the primary end of the research: the quantification of economic vulnerability.

Focus on the Means (Modeling) and the End (Vulnerability):

• Nature of the Model (The Means): The model is, in fact, inherently urban hydrodynamic in nature, which is crucial for determining the Flood Hazard. Without 1D/2D modeling (using HEC-HMS and HEC-RAS 2D), it is impossible to accurately predict the behavior of water depths (lâminas d'água) and their spatial impact for different return periods (TRs) and future climate change scenarios. Therefore, rigor in the modeling is fundamental.
• The Article's Core Focus (The End): The article is intrinsically focused on the Quantification of Socioeconomic Vulnerability within the Informal Economy. The economic aspect (losses in R$) is the direct consequence of the hydrodynamics (water depth). The depth and extent of the flooded area determine the impact, and this information can only be obtained through the aforementioned modeling.
• Target Population: Our specific and unprecedented concern was quantifying the losses of a particular segment of the population: street vendors (informal sector), who are extremely vulnerable to current climatic conditions and climate change projections. The manuscript has been restructured so that the Title, Abstract, and Introduction clearly reflect that the main objective is the risk assessment focusing on this specific vulnerability.

Nature of the Credit Claim/Recommendation:

We agree that a financial analysis was not performed to substantiate the feasibility of credit. The aspect of credit is proposed as a mitigating measure and financial impact reduction strategy for public managers, aimed at the rapid recovery of the low-income population whose livelihood is tied to the open-air market. It is, therefore, not a conclusion proven by the research, but a recommendation based on the high loss values quantified by our study. This recommendation has been clearly moved and framed within the dedicated "Recommendations and Policy Suggestions" section to avoid confusion with the core research findings.

Comments: The central part of the study consists of the hydrodynamic modeling performed for a specific location. However, the application of the adopted method was not presented with sufficient clarity. It would be more appropriate to define this element as a procedure that includes, among other things, a description of the applied algorithm and the underlying premises.

We appreciate the suggestion regarding the need for clearer presentation of the methodology. To address this aspect and reduce any ambiguity, we have incorporated a new figure that synthesizes the methodology in an easy-to-understand format.

This figure clearly illustrates the process sequence, from data inputs (e.g., rainfall, topography), through the modeling tools (HEC-HMS for hydrology, HEC-RAS 2D for hydrodynamics), the construction of the Depth-Damage Curve (DDC), and culminating in the final Risk analysis.

We believe that these modifications, particularly the inclusion of this visual procedure, make the application of the adopted method and the logic of the algorithm perfectly clear for the reader, detailing the underlying premises and the flow from Hazard calculation to Vulnerability assessment.

Comments: My overall assessment of the manuscript remains the same. I suggest again that the authors focus more on presenting the proposed methodology, complementing it with a corresponding algorithm (e.g., in graphic format), and revise the conclusions to ensure they are concise, derived directly from the research performed, and genuinely contribute to the advancement of the field.

We once again appreciate the feedback. As suggested, a new Figure presenting the Integrated Methodological Flowchart has been added.

This diagram clearly illustrates the applied methodological procedure, from the data input (hydrological and vulnerability) to the final calculation of Flood Risk and the quantification of economic losses.

We are confident that these revisions have significantly improved the methodological clarity and the robustness of the conclusions, aligning the manuscript with the required scientific standards.