Channel Bed Adjustment of the Lowermost Yangtze River Estuary from 1983 to 2018: Causes and Implications

Round 1

Reviewer 1 Report

Dear Authors,

your paper is very detailed and of high quality, value and relevance, however it does have some potentially serious weaknesses and issues that require further clarification:

-          the study is based only on one field survey campaign from 2018. It would be very valuable if there was at least one more control survey measurement.

-          some measurement parameters have not been specified entirely clearly, so the precision and relevance of the measured data is somewhat uncertain. (Ln. 180)

-          the quality, precision and relevance of the historical bathymetry data cannot be determined with certainty based on the given description. More detailed presentation of the used source historic bathymetry data would be necessary.

-          The method of calculating the digital model of the riverbed should be described in more detail (eg. why was the 50 m resolution chosen? Ln. 155)

-          Given all the uncertainties of the source data and used methods, the relevance and accuracy of conclusions is also debatable, especially since they contradict quite sharply other studies conducted in the Yangtze River Delta, that you cited (ln. 563, [12,28,73]). This discrepancy should be explained and discussed in more detail.

-          You also stated that the riverbed is being regularly dredged, which can potentially alter completely the effects of upstream anthropogenic and natural influences. This fact should also be addressed in the discussion in more detail.

Ln. 87. check grammar - i.e.

Ln .155 explain why the relatively coarse 50 m resolution was chosen. It would be desirable to show the original survey data along with tecnhical specification that was used to construct the digital model.

Ln. 178 seismic?

Ln. 180 decimeter level accuracy tied to a local navigation beacon with submeter accuracy – please specify the resulting final combined measurement precision.

Ln. 267, 268 & 269 a table showing the data would be useful.

Ln. 441 check grammar (may become shallower)

Ln. 526 – duns

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

The authors present a detailed analysis of the underwater morphology using the measured bathymetric maps of the downstream of Yangtze River Estuary, however, I cannot see much valuable conclusions, and suggest a major revision.  

(1) The introduction section is way too long with a lot of existing cognition, which should be simplified.

(2) “SCSP” should be defined in the text before its first usage, not only in the abstract.

(3) The paper cites a large quantity of references, which is not necessarily.

(4) Line 374-375, why the river discharge remains unchanged after the construction of the TGR? Please provide more information.

(5) The authors should provide the measurement season of the data used, that is because the underwater morphology may not be the same under flood and dry seasons, and that may bring in the problem of representativeness of the morphology evolutions.

(6) Although the paper gives a lot of discussions from different aspects, I suggest they should be simplified to highlight the key points, especially for the conclusions.

(7) Does the paper need so many authors and organizations? Maybe some of the co-authors could be noted in the acknowledgement section.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The authors revised the MS addressing all the comments raised and the quality of the MS is improved.