The Temporal Evolution of Coastlines in the Bohai Sea and Its Impact on Hydrodynamics

Round 1

Reviewer 1 Report (Previous Reviewer 1)

I have read the resubmitted manuscript and i believe it is worth publishing in this form.

Author Response

I have read the resubmitted manuscript and I believe it is worth publishing in this form.

Reply:

Thank you for your recognition and positive comments on our work.

Reviewer 2 Report (New Reviewer)

This review of changing coastal patterns around the periphery of the Bohai Sea in NE China is both a thorough and competent treatment based on a 34-year record mainly concentrated in three subregions: 1) Liadong Bay in the north, Laizhou Bay in the south, and the western area (proper) of Bohai Bay.  All are within  the inner part of what is commonly called the Yellow Sea.  The total length of the shores in this part of the Yellow Sea amount to 3,800 km and based on Figure 6, it appears that maybe 40 to 45% of the shore area has been affected by reclamation projects - most recently in the Tianjin area.  The main result of this study can be summarized by the surprising result that nearly 30m/yr is being built out into the bay and that this trend is having an effect on the M2 tidal rate of between 6 and 14 cm/year.

My criticisms are largely technical.  First, the images especially in Figures 3 and 6 that show areal views of encroachment into the different sub-basins are far too small in size.  As space is not a factor in the MPDI journals, I recommend that the images be clustered in no more that groups of four. (as in Figure 10).  This would expand the image width considerably and make it much easier to see the details.  Where other drawings show time-series change (s in Figure 12 for residual currents), the entire cluster of nine plots may be enlarged to take advantage of the full space available.  Second, the spacing within columns in Table 2 (which defines different coastal types) is very uneven.  The left side column is ok, but the middle and right-side columns show text that abuts directly against the lined margins of the figure.  Third, the English needs fairly extensive improvement.

The main resource utilized in this study is based on 45 remote-sensing images in a time series, which seems perfectly adequate for the study.  I have to admit that the equations presented in the Appendix are beyond my competency to judge, but the main results of the paper appear to be sound.

Author Response

The changes we have made in response to the reviewers’ comments are marked blue in the body of the revised manuscript. The detailed point-by-point reply to reviewers’ comment is enclosed.

Author Response File: Author Response.doc

Reviewer 3 Report (New Reviewer)

The Temporal Evolution of Coastlines in the Bohai Sea And Its Impact On Hydrodynamics

Abstract

1.      Line 18, the author mentioned the surface area decreased in the past few decades. this sentence is unclear and make me confused. What does the exactly surface area mean in here? The water or the land?  

2.      The abstract illustrated the study area of this article but did not provide enough information about the methodology, the involved dataset, and how coastlines in your study area changes from 1985 to 2018?

 

Introduction

1.      Line25- 26, the first sentence is hard to understand. The author described that the coastline would change due to climate change and human activities and provided some examples to help us understand the influencers that led to coastline change. Based on the first sentence, the author believed the effects of climate change can be divided into following examples, including sea level rise, coastal subsidence and coastal erosion.

Obviously, this sentence is not clear which does not give readers 100% correct information.

2.      Line 27-28, why are the links tough to understand? Is that because of the limitation of human resources, data, technology is not mature enough, or something else? I do not think the author described this idea clearly.

3.      Line 29-42, it seems the author aimed to show us there is some relationships between coastline change and hydrodynamics. But this part is not well-organized.

4.      Line 58-60, the author listed three previous studies, but they only give us the details of reference [24]. It is better to show us more details to illustrate how important your study is and what is the limitation of previous studies.

5.      What is your aim of this study? what is your innovation?

 

Materials and Methods

1.      Line 81-82, the author introduced the sea area and the length of coastline, the maximum depth and the mean depth. Where do these numbers come from? Do you calculate by yourself? By what methods? Or these come from others works and you do not cite?

2.      Line 86-87, same again. Where do these information and numbers come from? Please cite or illustrate clearly if you calculate by yourself.

3.      Line 96-103, the author briefly described the dataset involved in this study. However, they do not mention any details of the data. For instance, do you use all Landsat data in 1985, 1994, 2003, 2011 and 2018 without any selection processes? Besides, there is no specific time information of Google and ETOPO1 data. Google Earth utilizes MAXAR Digital Globe imagery, Planet, among other commercial imagery sources. What data was used here? The details of involved data source were not enough.

4.      Line 127-129, the author mentioned several steps in remote sensing image processing, but some steps even did not appear in the framework chart (Figure 2). Is Figure 2 include the complete steps in your study?

5.      Figure 3, Why some images represented in a false color composite and others not? It is better to mark these images as Figure 3 (a) (b) (c), etc. The description of this figure is not enough.

6.      Table 2, the author described the spatial location and identifiers of different coastline types. In Description of interpretation identifier column, the author gave us the details how they interpreted different coastlines from remote sensing image.

a)       Bedrock coastline, in what band composite would bedrock coastline show high reflectivity in white color?

b)      Sandy coastline, how do you trace line at the high tide level based on your data? The methodology did not describe the details.

c)       Estuary coastline and Lagoon coastline. How do you distinguish these two type near dams? It seems dams are important identifiers of these two coastline types.

d)      Lagoon coastline, in what band composite would lagoon coastline show high reflectivity in white color?

e)       Pond dam and protective dam. The spatial location of these two types are exactly the same, is it necessary to separate these two types?

f)       Marine construction coastline. I cannot find the image in Figure 3. Do port coastline and groynes coastline belong to marine construction coastline?

7.      Line 131-138, the author illustrated they build interpretation types for different coastline types and listed the descriptions and locations of different coastline types. Why did you reclass coastline types into 7 types in your study? Are these 7 types the common coastline type in your study area? What are the differences between them, especially in remote sensing image?

8.      Line 139-140. The author used human-computer interaction identification method to extract coastline from remote sensing data. Do you consider tidal correction? Is it necessary to have this step in your study area? And what about the precision test?

9.      Line 142, please tell us the version of ArcGIS and DSAS you used.

10.   Line 142-145, what kind of parameter did you calculate in DSAS to show the change rate of coastline? Do you use End Point Rate?

11.   Do you extract coastline in 1985, 1994, 2003, 2011 and 2018? I cannot find information in methodology.

12.   Line 144, Does “A total of 1414 change rates” mean you have 1414 transects to calculate the coastline change rate?

13.   Line 146-149, How many coastline types do you have in this article? You listed 7 types in Table 2, Line 131-138. But in Line 146-149, you said you only have 5 types?

14.   In 2.3.2 Land-sea grid construction, it is better to have images to show these three steps.

15.   In 2.4 Numerical adjoint model, what is the use of this model in your study?

16.   In 2.5 Estimation algorithm of spatially varying BFCs, what kind of information could we have based on this algorithm?

17.   Line 189, how do you know the deepest water depth of the computing area? How to calculate it?

 

Results

1.      Line 239, How do you distinguish reclamation and sedimentation in this study?

2.      Figure 7, it is better to put your coastline result in one whole image to illustrate coastline variations clearly.

3.      In abstract (Line 16-18) and Line 263, the author illustrated the coastline in the BHS became complex due to reclamation. Do you have any statistics, calculations or any other references to prove the boundaries became complex just because of the marine construction? How do you conclude the boundary became complex based on your study?

4.      Line 300, from Table 4, the Kinetic energy increased during your study period with fluctuations, not increased all the time.

5.      Figure 9, it is better to show location in these images as you analyze how the M2 tidal constituent propagates in Line 313-321.

6.      Figure 10 and Figure 11, please add location in these images.

 

Discussion

1.      Line 366, a 34-year record? Does this work focus the specific time between 1985 and 2018? It seems not a 34-year record. Is there any dataset involved in this work has a 34-year record?

2.      Line 366, the author used 45 remote sensing images and 5 individually maps in this study, but from the Methodology, we still have no idea of the details of these images and maps. Please complete the details of involved dataset in the Methodology.

3.      Line 367-369, How do you use the high-precision images in this study? The methodology is unclear.

4.      In 4.1 Evaluation of coastline change, this section gave us the information of coastline change in the study area. It is more like a Result, not a Discussion.

5.      In 4.2 Evaluation of hydrodynamics change, the contents are too short and should be well-organized.

 

Conclusions

1.      The conclusion is not well organized, you have to review your study in the first paragraph.

2.      Line 422-429, the conclusions is more like a conclusion of the Result, you should show the conclusion included the Discussion as well.

 Appendix

1.      It is better to put these things in the Methodology.

Author Response

The changes we have made in response to the reviewers’ comments are marked blue in the body of the revised manuscript. The detailed point-by-point reply to reviewers’ comment is enclosed.

Author Response File: Author Response.doc

Round 2

Reviewer 3 Report (New Reviewer)

Introduction

1.      Line27-28, the revised sentence seems more reasonable but still contains grammatical errors. Please revise the first sentence carefully.

2.      Line 72-74, this sentence is totally the same as the sentence (Line 15-17) in Abstract.

 

Materials and Methods

1.      Table 1, Path/Row of the data in 2003 & 2011 might be wrong, it should be 121/032, right?

2.      Line 157, the author used DSAS to calculate the EPR to show how coastline changed during the study period. How do you conduct coastline uncertainty? As I know, if you use DSAS to calculate EPR, you have to put in Default Data Uncertainty Parameter in Set Default Parameters. Did you used the Default Data Uncertainty provided by USGS or the number you calculated?

3.      How do you evaluate the accuracy of coastline you extracted from Landsat?

 Discussion

1.      The author deleted 4.1. Evaluation of coastline change in the latest version. It is better to analyze why coastline changed in this area. Based on the former version, I said the content was more like a Result because the author focused more on statistics. You should focus on the driving factors in the Discussion part.

 In general, the language should be edited carefully. There are still grammatical errors in the manuscript.

Author Response

The changes we have made in response to the reviewers’ comments are marked red in the body of the revised manuscript. The detailed point-by-point reply to reviewers’ comment is enclosed.

Thank you for your time and consideration of this manuscript.

Author Response File: Author Response.doc

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

I have carefully read the paper and I believe that it is an interesting study worth publishing.  This study concerns the coastline evolution processes and the diachronic changes occurred as a result of climate changes and human activities. In this study, the authors used satellite images, GIS and remote sensing technologies as well as a tidal model. In the introduction section the authors could also mention other methods for identifying the vulnerability of coastal systems.  The proposed references are the following:

· Pantusa, D.,D’Alessandro, F., Riefolo, L., Principato, F., & Tomasicchio, G. R. (2018). Application of a coastal vulnerability index. A case study along the Apulian Coastline, Italy. Water, 10(9), 1218.

·       Vittal Hegde, A., & Radhakrishnan Reju, V. (2007). Development of coastal vulnerability index for Mangalore coast, India. Journal of Coastal Research, 23(5), 1106-1111.

In the discussion section the authors could also mention coastal zone management methods in order to suggest solutions for the identified coastal changes in the study area. The proposed references are the following:

 

·       Saitis, G., Karkani, A., Koutsopoulou, E., Tsanakas, K., Kawasaki, S., & Evelpidou, N. (2022). Beachrock Formation Mechanism Using Multiproxy Experimental Data from Natural and Artificial Beachrocks: Insights for a Potential Soft Engineering Method. Journal of Marine Science and Engineering, 10(1), 87.

Overall, my suggestion is that the paper should be published after major revision mostly in grammatic and syntax.

 

 

 

Comments for author File: Comments.pdf

Reviewer 2 Report

Review of “Responses of hydrodynamics to changes of coastline in the Bohai Sea, China”

  

Lines 13,14: discussed > discusses, established > establishes - should be in present. The whole sentence should be re-written: e.g. This paper discusses the coastline evolution process and establishes identification of the coastal extent of an existing land reclamation.

Further in the abstract authors write again with grammar errors: time does not match with previous sentence. Either you should use only present time or present perfect for the whole section. It makes no sense to read and correct grammar in each sentence.

In general, figures 1-3, 5-10 are absent. It's impossible to follow the line if there is nothing behind the text. The English language expression needs to be improved. There were some sections where it was difficult to understand exactly what had been done because of the English expression.  

Reviewer 3 Report

I can't rate the article there are no figures and the article is not followed. Moreover, he does not explain the novelty and how his model is valid only calibrated with the M2 component and at a single point. 

Responses of hydrodynamics to changes of coastline in the Bohai Sea, China

Abstract:
I would try to avoid the first person and speak more impersonally. I would put in one line something about the methodology and about the novelty of the article vis-à-vis
the scientific community.
Line 100-106: But what's new, if there are already studies doing the same as the contribution there is?
Line 120-127: That is true, but it has been done previously as you have cited in the references above. So, what's new? Just one more study area?
Line 137: Always 4 m?(add a space between. 4 and m)Are there difference between spring an neap tide?
Line 138, 283: Format of M2
Line 139-140: Add the two point to the figure 1 and cite Where are the figures 1, 2, 3, 5, 7, 8, 9 and 10?
Line 220-233: format of the variables and units!
Line 283-284: Do you only validate with the M2 tidal constitute?in one point?Only RMSE? It is better to add R2
Line 320: The grid is the same?because if you change the grid you have to test again the variables

Even including the figures, I consider that there is nothing new in the article, in the introduction at the end it carries out the same previous studies but applying them to a different study area. In addition, you mention the use of a hydrodynamic model, which is only calibrated with a data with values of levels, therefore it is not enough to consider this model and therefore the results valid.