Introducing ICEDAP: An ‘Iterative Coastal Embayment Delineation and Analysis Process’ with Applications for the Management of Coastal Change

Round 1

Reviewer 1 Report

The paper deals with the implementation of an ArcGIS toolbox to automatically identify coastal embayments and quantify surface water change based on Global Surface Water Dataset. The tool has been tested along the coasts of South Korea identifying distribution and size of embayments and surface water changes.

The paper addresses the need of automatically identify and outlines coastal embayments overpassing the shortcomings of defining the ocean-coast boundary through visual interpretation/manual identification or automatic processing based on coastal elevation or drainage basin datasets.

The topic is original in the field since it deals with the issue on delineating coastal and estuarine waters that is a relatively unexplored topic within the academic community.

With respect to other published material, the paper presents a method that can be applied for delimiting seaward extent of embayments in a consistent and replicable way over extensive coastal areas. Moreover, the proposed methodology is based on datasets that are available globally ensuring its wide applicability.

The approach used to develop the ICEDAP tool is relatively simple being mainly based on the geometry of the coastline, but despite its simplicity (that can be seen also as an added value) it has been proved to be effective for delineating South Korea embayments. It would be interesting to experiment the application of ICEDAP tool to other areas with different coastal features.

Despite data and output visualization (i.e., figures and tables) should be improved (see specific comments below), in the complex, it is a very well-written paper that grab the attention on a not very much explored issue within the scientific community. The paper is also supported by a comprehensive and appropriate number of references.

Some comments addressed to specific sections are reported below.

Introduction

The introduction is well structured since it presents the topic from a broader perspective referring also to some of the policies on coastal water in Europe and USA. The aims and the novelty of the study are also well explained in this section. However, the reasons for the choice of South Korea as the area to test the effectiveness of the implemented tool are not very clear and can be stressed more in this section.

As a general comment, not only relevant to the introduction section, please note that it is advisable to write the abbreviations/acronyms (that are not immediately understandable) in their extended form the first time they are mentioned in the text. This is the case of “1 nm”, that it should be written in the extended form and its abbreviation included in the brackets (e.g., “…1 nautical mile (nm, 1.85 km)…”). The same can be applied to “EEZ” at the last line of page 2. On the contrary, it is not necessary to write “200 nautical miles” in full in section 2.1.2 (page 4) since it is not the first time “nm” is cited in the text. Similarly, “370 kilometers” can be written as “370 km”, in this case there is no need to write the unit of measure in full because it is of immediate comprehension for the reader.

At the seventh line from the bottom of page 2, “this research” is misleading since it is not very clear if it is referring to previous research of to the research presented in this paper.

 

Materials and Methods

The Materials and Methods section is well structured and the algorithm on which the ICEDAP tool is based is explained with enough detail. However, for the sake of replicability, it can be suggested to provide the reader with more information on the type/format of input data required by the tool. In particular, in Table 1, it is strongly suggested to include two additional columns/fields in which specifying: (i) the type of data format (e.g., shapefile, ASCII grid, GeoTIFF or other) required as input for ICEDAP tool; (ii) the website where to download the mentioned input data. If the table with the two additional columns does not fit page margins it is suggested to remove column one “Example”.

Additionally, the pre-processing of the datasets in Google Earth Engine should be described more in detail in the text.

Page 7: The sentence “These buffer products are used to trim away any seaward surface water from the embayment, leaving the remaining landward waters up to approximately 10 km inland and/or inflows with channel widths greater than 90 m.” is not easily understandable. In particular, it could be explained how the authors obtained 10 km and 90 m values.

Figure 4: Those depicted in Figure 4a are not geological characteristics as stated in the caption. Fig. 4a is an elevation map, please correct the caption. Additionally, the toponyms mentioned in the text should be in Figure 4 (i.e., Songho-Ri and Busan).

 

Results

The results are effectively structured into 2 sections reflecting the two main outputs obtained by applying the ICEDAP tool. However, the visualization of the results should be improved with reference to Figures 5 and 7. In particular, toponyms should be added to Figure 5 and/or coastal sectors (i.e., east, south, west) should be outlined in the map. It is advisable to use satellite images as base map of Figure 7 in order to make clearer where the land is. Moreover, it is advisable specifying the time interval to which coastal surface water gain and loss are referring to in Figure 7 caption.

 

Discussion

The discussion section includes some considerations on the results obtained by applying ICEDAP tool to the South Korea coasts in comparison with those of the previous works. Some remarks on the loss of coastal ecosystem services are also included and other potential applications of the implemented tool are described too. The only reviewer note regarding this part concerns section 4.1 in which the authors stated that regional-scale estimates of South Korean anthropogenically driven surface water change in the 8 km buffer is 1,417 km² but evidence of this estimate can not be found in the results sections. How was this estimated?

To conclude the reviewer would like to thank the authors for their attention and willingness in addressing the comments.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

The paper proposes a geometry-based ArcGIS toolbox to automatically delineate coastal embayments and quantify coastal surface water change. Such kind of tools are quite useful; however, the paper lacks in my opinion to appropriately present and document the added value of the proposed approach. I have the following comments:

1. Introduction

The state-of-the art of the proposed tool is not well documented. In the literature review where the need for such tools is presented, quite old bibliography is used. In addition, the reference to similar tools and their limitations is quite limited without making clear the gap the proposed tool is going to fulfill.

 

2. Methodology

Why is it important to create 9 geometric buffers? This sequence of buffers has been proved effective to assess the problem? Please add relevant bibliography.

In 2.2.3 the assessment of the anthropogenic alterations needs further explanation. 'We then eliminated portions of the estuary.... purposes.' Is this an automated processes or it is carried out manually?

In 2.2.4 Algorithm accuracy and validation.

There is not a real validation performed. The validation referred in the paper concerns the validation of the GSWD from bibliography. However, the statement 'We therefore supplemented existing estimates by visually interpreting high resolution time series Google Earth Images' is quite general and needs further explanation regarding (a) which time series were used and (b) which is the result of the accuracy after this process.

The breakpoint analysis applied needs to be more clearly presented in order to better understand that the 8 km buffer is suitable to represent coastal embayments in the study area.

Finally, since it is stated that it is and automated tool, it should be clearly described how automated is the application of the proposed  methodology. Is it a 100% automated process? In which steps the user has to intervene?

 

3. Conclusions

This section is missing.

English is quite good.

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

This manuscript develops a tool for automatically delineating coastal embayments and quantifying coastal surface water change from satellite remote sensing datasets. Briefly, this tool provides the ability to analyze coastal change at multiple spatial scales, and as such the tool is meaningful. However, there are still some issues that need to be addressed before publication:

(1)  What is the definition of “Embayment” in this paper, is it based on geomorphology or something else? Does the tool recognize “Embayment” in the same way as the geomorphological definition?

(2)  The “landmass separation” section is overly complex, and land-water separation using GSWD should be a simple task, but this section is obscure.

(3) The section "3.2. GSWD surface water change" used to represent land gain or loss is inaccurate. In coastal areas, satellite-observed changes in surface water extent may be the result of tidal effects and not actually the result of land gain or coastal erosion.

(4) Limitations and Uncertainties: Mentioning potential limitations of the ICEDAP toolbox, the satellite imagery data, or any other aspects of the study would provide a more balanced perspective on the findings. In order for other researchers to use this tool correctly, authors should describe the limitations of the toolbox in detail in the Discussion section, so that those using the tool have a clear understanding of its limitations and applicability.

Other minor comments (The manuscript doesn't have line numbers, so I can only locate the page numbers)

(1)  Page 2: “…all waters within 1 nm (1.85 km) of each…” nm is also an abbreviation for nanometer, so please give the full name the first time it appears.

(2)  Page 2: “… seaward edge of a country’s EEZ in…”  please give the full name of the EEZ the first time it appears.

(3)  Please note that some images are not of sufficient resolution, e.g., figure 1. Some maps are better with a scale, e.g., figure 4.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

In my opinion, the paper has been improved according to my comments and specific parts have become clear. Therefore, I agree to be published with minor editing of English language.

Minor editing of English language ισ required.

Reviewer 3 Report

The authors have significantly improved the manuscript. I have no further comments and think the paper can be published.