Study of the Long-Term Morphological Evolution of the Modaomen Channel in the Pearl River Delta, China

Round 1

Reviewer 1 Report

This study presents the evolution of Modaomen Channel in the Pearl River Delta from 1962 to 2017. The results and conclusions are clear. In the discussion maybe I would recommend to include the possible impact of these changes to the ecology of the system. Beside of this I find the manuscript easy to read and of potential interest by other readers.

Author Response

Thank you for reviewing the manuscript, and I will revise the work carefully to meet the demand of the journal. 

Reviewer 2 Report

In the present article entitled “Morphological Evolution of the Modaomen Channel in the Pearl River Delta over the Last 55 Years (1962–2017)” authors have analyzed the morphological modification of PRD for last 55 years. The topic of the article is relevant for the journal but novelty of the work is not clear. Methodological section is very poor. Need substantial modification before acceptance.

1. Need to modify the abstract section because it does not reflect the whole work.
2. Word already is mentioned in the title no need to mention again in the keywords, like Morphological evolution, Modaomen Channel; Pearl River Delta
3. Novelty of the paper is not clear. What new you have done in your article from the below mention articles.

https://doi.org/10.1186/s40623-020-01310-2

https://doi.org/10.1016/j.quaint.2020.05.047

4. Lithological character of the PRD need to mention in the study area section.
5. Methodological section is very poor. Revise it.
6. Mention the shortcomings and future scope of the study in the conclusion section.

Author Response

Thank you for your suggestion, and I will revise the work carefully to meet the demand of the journal.

(1) The “Abstract” has been rewritten. Please review it again and I look forward to your more valuable suggestions.

(2) The “keywords” has been rewritten as follow: Deltaic channel; Channel evolution; Human activities; Pearl River Estuary.

(3) The introduction section has been rewritten, and the novelty of the work has been highlighted. This work can help us to understand the long-term morphological evolution of a fluvial channel and add to the knowledge on the geomorphologic system of the PRD.

(4) I don’t think the two papers the reviewer mentioned (https://doi.org/10.1186/s40623-020-01310-2; https://doi.org/10.1016/j.quaint.2020.05.047) is related to this paper

(5) As the reviewer’ suggestion, the lithological character of the PRD is mentioned in the study area.

(6) The Methods section has been revised and the explanation is more detailed and clear.

(7) The second paragraph of conclusion section has been rewritten and the shortcomings and future scope of the study is added.

Reviewer 3 Report

Thank you for the manuscript entitled " Morphological Evolution of the Modaomen Channel in the Pearl River Delta over the Last 55 Years (1962–2017)", submitted to the Water journal. I found the article quite appealing with relevance to practical applications. Furthermore, morphological evolution of the river channel (bathygraphy) was presented in long-term period, which is not very common in the literature. However, before publication in Water journal, some major revisions of the paper are recommended. My general remarks are listed below:

• The introduction section should highlight the novelty of the work and how the paper differentiates from the wide literature on the subject, e.g. what new or modified methods were applied? Please provide some information about measurement techniques, used in similar studies. Moreover, the objectives of the paper were not stated clearly.

• In the study area section please provide the information about mean annual streamflow rates of the Pearl River in the Makou hydrological station. What is the area of the catchment, closed by the investigated site?
• The methods were described briefly and several questions should be made to the authors to provide more details and explanations. The authors used several bathymetric datasets from 1962 to 2017 – are they comparable in terms of measurement techniques? What was the precision of the depth measurements? Furthermore, why the kriging interpolation technique was used? This should be explained in the context of previous studies. It would be also beneficial if the authors will expand the statistical analysis – in the current form it is quite simple and descriptive.
• Results are properly visualized, however, this paragraph should be rewritten in more sophisticated way to improve clarity. Moreover, please try to combine subparagraphs 4.1.1, 4.1.2, and 4.1.3. Maybe some hydro-climatological background of the analyzed period will be sufficient as a part of this paragraph?
• Figure 6 – Probably the figure b) presents change rate of water depth. Furthermore, depth never becomes negative in value!
• Figure 7 – I am not sure if line chart in the case of the widths, depths, width-depth ratios, and thalweg elevations is correct, as line chart is used for continuous data visualization. Such mentioned parameters, measured in the channel cross-sections, are not in continuous type of the data. This remark is also addressed to another charts.
• Figure 9 and 10 – please delete black border (outline).
• In discussion section please provide some additional references from another regions of the world.

Author Response

Thank you for your suggestion, and I will revise the work carefully to meet the demand of the journal.

(1) The introduction section has been rewritten, and the novelty of the work has been highlighted. This work can help us to understand the long-term morphological evolution of a fluvial channel and add to the knowledge on the geomorphologic system of the PRD.

(2) The Methods section has been revised and the explanation is more detailed and clear. These bathymetric data are provided by the Waterway Bureau of Guangdong Province, which is a professional institute for waterway maintenance and survey. All the data has the same mapping scale, plane coordinates and bathymetric. Although there will be some differences in measurement methods in different years, we think it is not a key problem to be considered in this paper. In addition, the Kriging interpolation method is a common method in geoscience statistics, which can generate DEM very well.

(3) Some hydro-climatological analysis background has been analyzed in discussion section, so we focus on the morphological changes of the Modaomen Channel in the result section

(4) In Figure 6 and Figure 7, all the line charts have been revised as column charts, and the water depth has been revised as positive value.

(5) In Figure 4, Figure 6- Figure 10, the black borders (outline) have been deleted.

(6) Some additional references from other regions of the world has been added in the discussion section.

Round 2

Reviewer 2 Report

The authors have modified the manuscript as per the reviewers comments.  Now it can be accepted for publication.

Reviewer 3 Report

The authors addressed all the comments raised by the Reviewer. The manuscript has been slightly improved and the authors have tried to do their best, so I would recommend the acceptance of the manuscript for publication in Water journal.