Predicting Future Urban Flood Risk Using Land Change and Hydraulic Modeling in a River Watershed in the Central Province of Vietnam

Round 1

Reviewer 1 Report

Dear authors,

This is interesting research, and there is no duplicate. However, I would suggest you modify your research before considering the publication process. Please check all the minor mistakes bellow: 

The manuscript is interesting in a territory's sustainable development and worthy for publication in this journal. The article discusses a method of assessing flood risk for different exposures and vulnerabilities in 1995, 2019, and 2040 by combining land-use change and hydraulic models. It was carried out in central Vietnam in an area with high exposure risks to floods and a large group of vulnerable communities. The results might be significant and reduplicated in other regions. I do have several comments as follows:

1) For the study area characteristics, it is necessary to outline the relationship between the watershed and Quang Ngai province.

2) I would like to see the samples' locations since training data is considered an essential element in accurately classifying satellite images. This article, unfortunately, falls short on that front.

3) The authors use three parameters: scale, shape, and compactness in the satellite image classification process. However, it does not provide these respective parameter values

4) For 2040 land cover prediction, the authors used input variables such as altitude (5 m DEM), slope inclination (%), and distances from roads, developed area in 1995, and from water (river or sea). An explanation for the selection of these factors would be of value.

5) Line 142, what is the MIKE NAM model? It is essential to explain this in more detail.

6) My other concerns with this article are on the Analytical Hierarchical Process (AHP). For the main part, this method is based on experts' decisions, but not decision-makers. The decision-makers should be involved in the analysis process. An explanation is needed on why AHP was selected and why decision-makers were not involved.

7) Even though the theory of flood risk assessment is strong in this study, there are limits indicators for each risk element. For example, the authors use only two indicators (poverty rate and the number of hospitals) to construct a vulnerability map. I feel the authors need to put forth more explanation, maybe related to the available data.

8) The results and discussions highlight the study's findings. The authors should, however, also discuss the study's limitations and future prospects.

Specific comments:

Format: Line 1: Choose the type of paper.

Abstract: 

Please rewrite the second sentence, see bellow:
Phrasing suitable land planning strategies requires assessing future flood risk and predicting the impact of urban sprawl.

Rewrite the third sentence, as bellow:
This study aims to develop an approach combining land-use change and hydraulic models to explore future urban flood risk, aiming to reduce it under different vulnerability and exposure scenarios.

Line 22: Delete "with respect to" instead for "concerning" add here

Line 27: please add a comma before AND. check through the paper!

Line 30: this sentence should be considered writing in the active voice, as bellow:
We have compared the flood risk in 1995, 2019, and 2040.

Line 34: related to risk!

Line 35: delete Of

Line 35: decision-making

Line 48: Line 48: complex is often overused. please change to complicated. 

Line 53: AND again. Please find, check through the paper, add a comma before AND. I will not mention it again.

line 59: distance to the active channel. adding an article THE

Line 61: et al.
Please check through the paper.

Line 61: delete HAVE

Line 63: delete IMPORTANT, consider change to ESSENTIAL to improve your sharpness writing.

Line 64:
"From this study": wordy.
change this sentence to the active voice, see bellow:
The authors classified flood risk indices into three components; social-economic, physical, and environmental.

Line 70: Delete "confined.

Line 71: wrong order. Changing the word order:
aggravating risk causes.

Line 72: add a comma before According to.

Line 74: Time periods: redundant. please remove TIME

Line 75: delete IMPORTANT, using ESSENTIAL

Line 76: "This" what you mean? it is an unclear antecedent. please clarify this subject.

Line 77: please add the article THE before "future"

Line 78: Delete phrase words: AS AN APPROACH. it is unnecessary in this sentence.

Line 81: Consider to rewrite this sentence to the active voice, see below: In this study, we designed to examine this
hypothesis by evaluating the flood risk for different exposures and vulnerabilities, which is very important in spatial planning and sustainable development to mitigate risks.

81: Remove "Can be directly attributed to a decrease of poverty".

Line 84: specifically: often overused. May change to: examines explicitly!

Line 88: add a comma before WITH

Line 89: This sentence is wordy. please rewrite it to avoid in, its, is, and, the, to, with, this, that. See bellow:
This area's population is overgrowing, increasing from 1,218,600 persons in 2010 to 1,231,697 in 2019, with most of this occurring in the alluvial plains subject to floods.

Line 97: Change watershed to watersheds

Line 104: AND can not go with IS, please rewrite this clause.

Line 107: Change "In addition to causing 41 deaths, the November 2013 flood resulted in the evacuation of nearly 1700 households alongside other substantial damage and is considered one of the most significant damage-causing events in Quang Ngai province's history." To "In addition to causing 41 deaths, the November 2013 flood resulted in nearly 1700 households' evacuation alongside other substantial damage and is considered one of the most significant damage-causing events in Quang Ngai province's history."

Line 214: Change to obtained to were obtained

Line 271: change R2 to R²

Line 275: Change R to R²

Line 280: Change flow depth to flood depth

Line 309: Change transition in land cover to land cover transition

Line 409: Change socioeconomic to socio-economic

Line 410: delete BY, change to Divide into.

Line 414: Change an assessment of to: assessing

Line 415: Delele THE before FLOOD RISK

Line 422: Floods, not flood. Delete IN TERMS OF, change to REGARDING

Paper's format: 

Please check the journal's format: Check my comments for Chapter 3. Methods.

Please adjust the format for this sub-heading, no TAB for all titles.

Thanks.

 

Comments for author File: Comments.pdf

Author Response

Thank you for your comments, time, and efforts. A comprehensive response is attached. The Authors

Author Response File: Author Response.doc

Reviewer 2 Report

 

The manuscript is interesting. Nevertheless, it needs some further improvement before being accepted for publication. In general, there are still some occasional grammar errors throughout the manuscript, especially the article "the", "a" and "an" is missing in many places; please make a spellchecking in addition to these minor issues. The reviewer has listed some specific comments that might help the authors further enhance the manuscript's quality.

 

1. Specific Comments

 

Please include a list of acronyms and abbreviations.

 

• Introduction

• The objectives are not explicitly stated.
• The authors need to enrich the background further. you may review other additional relevant references.
• What is the novelty of this work?

 

• Methods

• I would suggest showing the methodological approach through a flowchart
• Methodology limitations should be mentioned.
• All variables should be explained.
• Please justify why your model-approach is feasible?
• What was the data resolution used in the computations?

 

 

• Results

• This section is well written.
• Please improve the all figures resolution and text size, also remove the frame of the figures.

 

 

• Discussion

The discussion should summarize the main finding(s) of the manuscript in the context of the broader scientific literature and address any limitations of the study or results that conflict with other published work.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Author Response

Thank you for your comments, time, and efforts. A comprehensive response is attached. The Authors

Author Response File: Author Response.doc

Reviewer 3 Report

Brief summary:

The topic and research presented in the manuscript entitled “Predicting future urban flood risk using Land Change and Hydraulic modeling in Tra Khuc river watershed, Vietnam” is highly actual and interesting for readers of the Remote Sensing journal. The authors demonstrate solid knowledge of the presented approaches as well as data processing. The questions being addressed are practically important not only for effective flood risk management, but also for spatial planning. Despite this, I have several comments that authors shall consider for improving the content and quality of the presented manuscript. Overall, these comments characterize a major revision.

 

Comments:

1. Introduction section – The literature should be reviewed more thoroughly. The emphasis should be placed on current trends, methods and relevant works in:

- The field of land use/land cover classification, change and scenario modeling. See for example:

- https://doi.org/10.1080/0143116031000139863

- https://doi.org/10.3390/rs12071135

- https://doi.org/10.1016/j.apgeog.2010.11.007

- The field of hydrologic-hydraulic modeling. See for example:

- https://doi.org/10.1016/j.envsoft.2017.01.006

- https://doi.org/10.1007/s11027-015-9654-z

- https://doi.org/10.1016/j.pce.2010.12.011

- The field of flood risk assessment and spatial planning. See for example:

- https://doi.org/10.1007/s11069-008-9244-4

- https://doi.org/10.5194/nhess-9-1881-2009

- https://doi.org/10.2166/wp.2018.077

2. Line 113 – Use “Data and Methods”.

3. Line 113 – Section 3 – A flowchart with methodological workflow would be useful for the reader for better orientation in the methodology applied.

4. Lines 138-139 – How were the cross-sections prepared? Were they measured in the field using some GNSS device? or Were they inserted manually into the model within certain distance based on digital elevation model? Can you show cross-sections in new figure along with the 2D computational mesh and other input data for preparing the hydraulic model?

5. Line 150 – Topographic map 1:10 000, as a source for DEM, is certainly a limitation for 2D hydraulic modeling. What could be the effects of using LiDAR data instead? I believe that this issue should be at least discussed in Discussion section.

6. Lines 165-167 and the like – Unify the terminology for using the terms “land use” and “land cover”, as there are differences in these terms. I suggest to use only the term “land cover” or “land use/land cover”.

7. Lines 289-293 – The classes of flood hazard (very low, …, very high) are mentioned, but the map in Figure 4(c) is not classified into these classes. It will be useful to add Figure 4(d) with classified flood hazard map into mentioned classes. In addition, the classification method used (e.g. natural breaks) should be also mentioned in the text.

8. Line 323 – Multi-Layer Perceptron (MLP) is mentioned here, but it is not described in the Data and Methods section.

9. Line 329 – Reference to “Figure 7a, 7b” does not match the caption for Figure 7.

10. Line 476 – “Maya Golden Landscape (MGL)”???

11. Line 397 - Discussion should be also focused on limitations and uncertainties, which may arise from the data and methods used. In this sense, you should also focus on the following issues confronting them with relevant literature sources:

- Discuss the applied object-oriented classification (OBIA) technique with other techniques for image classification. What are advantages of OBIA against other approaches?

- Discuss the limitations in input data (especially DEM, cross-sections) used for hydraulic modeling. See, e.g. https://doi.org/10.1111/j.1753-318X.2009.01029.x

- Discuss the AHP method used for assigning weights for hazard, exposure and vulnerability maps. What are advantages or disadvantages this method? What other methods could be used instead?

- Discuss and justify the use of natural breaks method for classifying the final flood risk maps. Can you at least support the choice for natural breaks method with some literature sources (line 265)? How will the final flood risk maps change when using other classification methods (quantiles, geometric interval, etc.)? The coverage of flood risk classes presented in Table 14 will probably change when applying other methods.

12. Figures 4-12 – Enlarge these figures, especially, the legends, north arrows and map scales used in these maps, as they are difficult to read.

13. Figure 4 – Use also units for depth and velocity in the legend of these maps.

14. Figures 5a, 5b, 6 and 7 could be presented as one figure divided into a, b, c and d.

15. Figure 10 – Figure caption (a, b, c are mentioned twice) does not match its division. I suggest to show poverty maps in left column and maps with the number of hospitals in right column.

16. Figure 12 – In each of the three presented maps indicate the year or a, b, c, d for which each map corresponds.

17. Table 10 – Is the term “Developed” equal to terms “Built-up area” or “Urban area”? If yes, then rename it in the whole manuscript either with “Built-up area” or “Urban area”.

18. There are too many tables in the manuscript. I think that Tables 2, 3 and 4 could be presented as one table. The same applies for Tables 5, 6 and 7. Then, Tables 1 and 8 can be deleted, as they are well-known from literature – instead of these two tables provide appropriate literature source(s), where they can be found.

19. English language should be corrected in several places, e.g. “Flood risk is significantly challenging sustainable spatial planning” (line 22), “satisfies a given criteria” (line 222), “there are three main components in this study: there are three main components in this study:” (lines 228-229), “sun” (Table 4), “Equation importance” (Table 1), “In general, the coastal plains in Vietnam in general and in the study area” (line 404), etc.

Author Response

Thank you for your comments, time, and efforts. A comprehensive response is attached. The Authors

Author Response File: Author Response.doc

Round 2

Reviewer 2 Report

Accept.

Reviewer 3 Report

The authors performed a substantial revision of the manuscript according to the given suggestions and comments. I spotted few very minor things that should be corrected, but this could be done during the production process. Therefore, my final recommendation is to accept the manuscript in present form.

Suggested corrections:

The term “developed” needs to be changed in some places into “built-up area” (lines 329, 341, 346, 354, 356, figure 7c) as well as “land use” into “land cover” (table 1, lines 25) to be consistently used in the whole manuscript. In addition, there are some typos, e.g. “the2019classification”, “,, weas”, etc.