Round 1

Reviewer 1 Report

This study gives an important useful and very detailed sattelite data analysis of land surface levels of an dense populated islandin Asia. However it is not an inundation risk analysis or possible mitigation measures assessment, neither is it directly relevant for SLR impact assessment. Natural but temporary hydrodynamic hazards, enhanced by seasonal and tidal seawater level variations and SLR define the real inundation risk.  In this study only a static evaluation of land surface levels is presented.

It shows that  land subsidence in the muddy and low coastal areas is the real problem. The main cause of this land subsidence is ground water extraction and drainage. SLR just adds a little additional risk. The main cause of flooding is lack of natural protection by mangrove forests, beaches and embankments.

The societal relevance is high, but the scientific contribution lays mainly in the way of statistical / mathematical sattelite data analysis, which is novel but relevant for sattelite data specialists only. The geophysical implications of land subsidence, storm hazards and SLR should be better explained, perhaps by a colleague with coastal engineering background.

These considerations should be better emphasized in summary and conclusions.

English language and style should be thoroughly checked.

See attached document for detailed comments.

 

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

General comments

The topic is interesting, and the approach is novel. On the other hand, the authors do not clearly present their methodological approach (missing resolution information of the EO products that they used). Also, the Introduction section needs to be enhanced.

The study area must be separated from the methods.

The discussion has mentioned as a section but it is completely missing in the text.

Results need to be better presented. Also, a few times settlement distribution is mentioned, and the author should provide a settlement distribution map from e.g. the Copernicus products

The maps of Figures 4 and 6 do not have the same size. Maps in Figure 4 seem to be deformed.  Also, legends must be more informative (etc add mm/year in the color scale)

Sea level rise scenarios of low and high risk are mentioned but I could now clearly identify them in the text.

I did not go into detail in the results since many things need to be clarified in the above sections to support their arguments.

Also, even that I am not a native English speaker I have noticed that the English language needs to be improved.

More in the PDF file.

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Thanks for the revision.

Author Response

Dear,

Thanks very much for taking your time to review this manuscript. I really appreciate all your comments and suggestions! 

Then during the revision process, I can recognize the editor's and reviewer's professional responsibility, which is deserving of my appreciation and learning from it. It will be very beneficial and instructive in my future studies.

In the revision, I revised some English problems and do some minor revisions.

Thank you again for your help in my study and look forward to your reply!

Reviewer 2 Report

General comments

The author made a great effort in improving the manuscript and some parts have become clearer. On the other hand, the authors still need to improve the presentation of their work, since still some parts seem to be misplaced.

A discussion section is needed.

Also, even that I am not a native English speaker I have noticed that the English language needs to be improved.

More in the PDF file.

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.docx

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

The present manuscript describes an interesting use of the InSAR data to predict coastal inundation in view of future sea level rise (SLR) and subsidence. The topic is of paramount importance for the worldwide community, the present contribution looks more like a report than like a scientific article. Further, I cannot see this as a crucial contribution for the scientific community, but as an application of a methodology which is already well known since years.

I thus believe that this contribution cannot be accepted in the present form but requires a strong improvement to be considered for publication.

One of the main problems is the English use, in terms of grammar, syntax and clarity of sentences. Since such issue exists throughout the paper, I cannot go into depth and suggest the use of an English editing service.

Then, the novelty of the present manuscript must be definitely highlighted.

All along the text, citations must be thoroughly checked and properly adjusted, as well as the references in the end of the paper, whose format must be double checked.

 

In the beginning of the introduction, some references are needed when talking about NOAA and IPCC.

In the end of the introduction, a better discussion of the coastal inundation should be provided. With this purpose, I suggest:

• moving most of section 2.4 to the introduction section,
• improving the description of the most used tools for coastal inundation predictions.

For instance, as discussed in section 2.4, numerical modeling is of paramount importance and is often combined with remote sensor data. Hence, some approaches recently applied for coastal flooding purposes could be briefly recalled (e.g., Apollonio et al., 2020; Gaeta et al., 2018; Jang et al., 2020; Postacchini et al., 2019; Postacchini & Ludeno, 2019; Torresan et al., 2019; Tsoukala et al., 2016).

 

The population data provided in the beginning of section 2.1 should be checked and revised.

In the first paragraph of P3, Figure 2 (and not 1) should be recalled.

Some acronyms are never introduced, please check throughout the text (e.g., see DEM and POD at P4).

Section 2.3 is hard to be read and should be thoroughly revised.

At P5, the sentence at lines 2-3 (“Considering … accurate results”) should be moved later after the SBAS-InSAR description.

In addition to the displacement of section 2.4 to the introduction (see previous comments), some words should be spent about the role of rivers and adaptation measures, although such variables are not here accounted for.

 

I would prefer the same color range for both panels of Figure 5. Further, to better characterize the whole island, why not combining both ascending and descending orbit data?

Check the x axis of figure 8, it should start on January 2018, right?

Why are the InSAR results not shown in Figures 9 and 10? Such results are recalled in the text (section 3.1, P10-11), but never illustrated.

Figure 12 is wrongly recalled at P10, please revise.

While sections 3.1 and 3.2 only illustrate some pictures and InSAR data, I believe that the most relevant result of the paper is described and shown at section 3.2, but this is only briefly presented. Please expand.

The reason why the authors’ results are better than other available data must be well motivated (end of section 3.2).

A better illustration of the results should be provided, in addition to Figure 11. For instance, a comparison between the two inundation scenarios at some regions of Penang could be illustrated.

 

References

Apollonio, C., Bruno, M. F., Iemmolo, G., Molfetta, M. G., & Pellicani, R. (2020). Flood Risk Evaluation in Ungauged Coastal Areas: The Case Study of Ippocampo (Southern Italy). Water, 12(5), 1466.

Gaeta, M. G., Bonaldo, D., Samaras, A. G., Carniel, S., & Archetti, R. (2018). Coupled wave-2D hydrodynamics modeling at the Reno river mouth (Italy) under climate change scenarios. Water, 10(10), 1380.

Jang, D., Joo, W., Jeong, C. H., Kim, W., Park, S. W., & Song, Y. (2020). The Downscaling Study for Typhoon-Induced Coastal Inundation. Water, 12(4), 1103.

Postacchini, M., Lalli, F., Memmola, F., Bruschi, A., Bellafiore, D., Lisi, I., ... & Brocchini, M. (2019). A model chain approach for coastal inundation: Application to the bay of Alghero. Estuarine, Coastal and Shelf Science, 219, 56-70.

Postacchini, M., & Ludeno, G. (2019). Combining numerical simulations and normalized scalar product strategy: a new tool for predicting beach inundation. Journal of Marine Science and Engineering, 7(9), 325.

Torresan, S., Gallina, V., Gualdi, S., Bellafiore, D., Umgiesser, G., Carniel, S., ... & Critto, A. (2019). Assessment of climate change impacts in the North Adriatic coastal area. Part I: A multi-model chain for the definition of climate change hazard scenarios. Water, 11(6), 1157.

Tsoukala, V. K., Chondros, M., Kapelonis, Z. G., Martzikos, N., Lykou, A., Belibassakis, K., & Makropoulos, C. (2016). An integrated wave modelling framework for extreme and rare events for climate change in coastal areas–the case of Rethymno, Crete. Oceanologia, 58(2), 71-89.

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

The article "Flood Inundation Analysis in Penang Island (Malaysia) Based on InSAR Maps of Land Subsidence and Local Sea Level Scenarios" presents the results of the application of SBAS technique to infer subsidence in the coastal scenario of Penang Island. The authors also try to find correlations between subsidence and land inundation.

The paper is badly written, in a not-acceptable english style for the scientific standards. Moreover, most of the figures are approximately presented (maps without scale or north arrows, time series with wrong axis, photos without location on the maps), as well as some numbers are incorrect (see section 2.1, for instance).
The results of the SBAS analysis does not add any significant content to the scientific literature. Besides, I suggest to the authors to obtain vertical and horizontal component to have a more reliable analysis of the subsidence phenomenon.
The correlation between subsidence and inundation map, even if promising, is badly presented and I do not see any quantitative analysis which are worth of discussion.

A discussion section, where the significance of the results is shown and a comparison in the scientific panorama is provided, is totally missing.

Therefore, I suggest to reject the paper as it is, encouraging the authors to sensibly improve it.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

This is a very intereting study. I enjoyed reading the manuscript. Nevertheless, it needs some further improvements. 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 • Introduction • The objectives should be more explicitly stated. • The authors need to enrich the background further. The following literature (which are just suggestions) might be useful in this regard >, > ,you may review other additional relevant references as well. • What is the novelty of this work? • Methods • The methodology limitation should be mentioned. • All variables should be explained. • Results • This section is well written. • Please improve the figures resolution and text size. • 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

Please see the attachment

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The new version of the manuscript has improved, but some points still require attention.

At first, the English use still requires a thorough revision. Many parts of the manuscript, especially the new ones, are often unclear.

In the introduction, I suggest the author to talk not only of simple numerical modelling (P3). Rather, the paragraph could be improved briefly talking of the use of remote sensors (like cameras or marine radars) and their combination with numerical modelling, this leading to heavy computations, though important for a detailed evolution of wave and inundation processes (e.g., Rutten et al., 2016; Postacchini & Ludeno, 2019).

As suggested in the first-round review, the authors should highlight the novelty of their work in the introduction.

Some issues with figures:

• Fig.1 looks doubled.
• Figures 3, 6, 8 are incorrectly embedded within the text, with caption some lines far away.
• Only one out of two panels of Fig.8 is visible.
• Fig.10 should be made of two panels, and not four (these are replicated two by two).

In section 2.3, the sentence “Considering that, the SBAS-InSAR technique … than other MT-InSAR” should be moved after the description of the SBAS-InSAR technique, i.e. in the end of this section.

Title of section 3 should be renamed as “Results and Discussion”.

I do not properly understand the sentence “The severe settlement area…uplift” in the end of P8.

As suggested in my previous review, citations all along the text and the reference list must be double checked.

 

References

Postacchini, M., & Ludeno, G. (2019). Combining numerical simulations and normalized scalar product strategy: a new tool for predicting beach inundation. Journal of Marine Science and Engineering, 7(9), 325.

Rutten, J., de Jong, S. M., & Ruessink, G. (2016). Accuracy of nearshore bathymetry inverted from X-band radar and optical video data. IEEE Transactions on Geoscience and Remote Sensing, 55(2), 1106-1116.

Reviewer 2 Report

Dear authors,
I would like to thank you for the massive re-organization of the paper.
However, the paper has almost completely changed, both in the introduction and in the results. 
Still many problems can be observed, both in the language, in many sections with wrong construction of the sentences and with many typos, and in the characterization of the results. In general, the paper still does not show any particular innovation, although the theme is very interesting.
According to my judgement and my experience in the field, considering the processing of both ascending and descending geometries, the reprojection along the vertical and horizontal components must be shown, especially when dealing with subsiding areas. If not, the processing is not correct. The R² shows that asc and desc results are not very well correlated, thus highlighting some problems in the processing.
The correlation between soil type and subsidence rates is not significant without any geotechnical and geological data, as well as the comparison between the SLR modeling and the subsidence is still qualitatively analyzed.

Therefore, I confirm my previous judgement, still encouraging the authors to re-process DInSAR data and resubmit the paper with clearer ideas and more quantitatively analyses.

Reviewer 3 Report

Accept.