Seasonal Variation of Catenary-Bead Dunes in the Yangtze River Estuary: Causes and Implications

Round 1

Reviewer 1 Report

Please find the attached File

Comments for author File: Comments.pdf

Author Response

Reviewer 1

Dear authors, thank you for the opportunity to review this work. The manuscript presents a study on the morphological variation and developmental characteristics of catenary-bead dunes in the dry and flood seasons. It is very interesting and shows important results, certainly in accordance with the scope of JMSE. The manuscript includes an introduction with a detailed description of previous studies, a description of the comprehensive survey, research description, an extensive discussion of the results and conclusions with a summary.

[Author’ response]: We would like to sincerely thank you for your valuable time in re-reviewing our manuscript and your kind support. In the revised version, we have carefully revised the manuscript according to your suggestions. All changes/additions are highlighted in red fonts. We hope this explanation meets your expectations. Thanks again.

Minor comments below:

L40 The year of the cited publication (Ashley) is missing in the text. The same comment for L49, L54, L235, L238, L248, L260, L291

[Author’ response]: Thank you for catching this issue. We have checked the whole manuscript and added years of these cited references.

L43 As mentioned, different sediment contents can lead to different dune geometries under similar flow conditions. A recent study demonstrated that the use of natural-based additives can increase the degree of sand cohesion inducing dunes to increase their resistance to erosion, resulting in different dune geometries under similar flow condition. The reference may be useful to include:

https://www.mdpi.com/2077-1312/9/6/620

[Author’ response]: Thank you for your kind help. Added. Please see lines 284-286.

L46 Several studies on dune evolution and morphodynamics have been performed both in

laboratory and field settings. The following reference on a recent comprehensive review

concerning the beach–dune system morphodynamics should be nice:

https://www.mdpi.com/2077-1312/10/5/627

[Author’ response]: Thank you for your suggestion. We have cited this reference. Please see lines 239-240.

L88 The mentioned figure should be Fig. 1b, as in the rest of this section

[Author’ response]: Thank you for catching this. Modified. Please see line 86.

Fig.1 As defined of the introduction, the MBES is a tool for collecting high-resolution bathymetry. Since detailed information regarding bathymetry is not shown in Fig.2, the sentence “MBES: multi-beam echo sounder system” might be removed from the caption. The definition of the site map is enough.

[Author’ response]: Thank you for catching this. Revised and removed.

L138 Acoustic Doppler profilers are able to measure velocity within a minimum limit depth, beyond which it is impossible to have an accurate measurement because the instrument does not have enough space to emit the acoustic wave and record its return; that is why a blank area is given in the bottom boundary layer. A briefly explanation on the reason for choosing the velocity of 1-2 m/s in the boundary layer would be appreciated.

[Author’ response]: Sorry for the confusion. We have checked and modified this mistake. Actually, previous studies also cannot measure the bottom velocity and they usually use the velocity near-bed about 1-2 m on the riverbed (Zheng et al., 2016). So, we changed the sentence to: Thus, the bottom velocity in this study was replaced by the velocity near-bed approximately 1-2 m on the riverbed[20]. Please see lines 136-138.

Reference

Zheng, S.W; Cheng, H.Q.; Wu, S.H.; Liu, G.W.; Lu, X.J.; Xu, W.X. Discovery and implications of catenary-bead subaqueous dunes. Sci. China Earth Sci. 2016, 46(1), 18-26.

L144 As stated, the parameters H and L are measured considering minimum of three cross-section profiles along the dune; in the following, the maximum dune height (H) and dune length (L) were selected in this study. A briefly explanation on a rationale for this contrariwise choice would be appreciated.

[Author’ response]: Sorry for the confusion. Thank you for your careful review, here, we made a mistake. Now, we changed these sentences to: Because catenary-bead dunes have variable height and length, these parameters were measured at least of three cross-section profiles along the dune (Fig. 2). Since elliptical pits will add to the dune height, the cross-section profiles were set to pass through the center of these pits. In this study, the maximum dune height (H) and the corresponding dune length (L) were selected as the measured dune height and length, respectively. Please see lines 140-145.

Fig.2 The dune heights (H) in the three panels should be H’, H’’ and H’’, according to the other parameters. In addition, Fig.2 should be mentioned in the text. Since Fig.3 is presented before Fig.2, the two pictures could be switched.

[Author’ response]: Thank you for your kind help. We have revised the Fig. 2. We have deleted the “Fig. 3” in line 138 (older version) and this change has no influence on the description of the manuscript. Thanks again.

L166 The mentioned figure should be Fig.3a and Fig.3c

[Author’ response]: Thank you for catching this. Modified. Please see line 166.

L172 The mentioned figure should be Fig.3c

[Author’ response]: Revised.

Table 1 Since data of morphological characteristics change of bedforms are reported only in case of the lee-side angle of about 16.7 ° and not in case of other dune types (such as linear and curved dunes), you could specify the limitation of reported data in the caption.

[Author’ response]: Thank you for catching this. Modified.

L191 The mentioned figure should be Fig.3b

[Author’ response]: Thank you for your suggestion. We have changed this. Please see line 193.

Eq.4 There is a typo in the value of R2 of red line. Should be 0.182 according to Fig.4

[Author’ response]: Thank you for your kind help. We have modified the Eq.4. Please see line 202.

Table 2 Two records are reported for the flood season and the dry season. A description of the distinction between #1 and #2 might be helpful.

[Author’ response]: Thank you for your suggestion. Actually, grain size contents of samples #1 and #2 (Oct. 2014) are similar, and meanwhile, samples of #3 and #4 (Feb. 2015). So, we added a description about these data below Table 2. Please see Table 2.

Again, thank you very much for your valuable time in reviewing our manuscript. We hope the changes/additions meet your expectations.

Author Response File: Author Response.docx

Reviewer 2 Report

This is a well written and well reserched contribution which clearly describes the characteristics of Catenary-Bead dunes in the YR. It is good that the conditions which favour the formation of these features are noted.  I think that more detail could be provided about the locations where the sediment sampes were collected (e.g. from a dune or a pit or a combination of both) given this appears to be a significant factor. 

It is noteworthy that the relationships illustrated in Fig 4 are medium to weak (e.g. the red line associated with dry season Dunes) which suggests that other factors may be in play.

The following minor changes are proposed:-

Line 20 - Change to - ....dunes are higher than....

Line 22 - Change to  ...... types yield a.....

Line 23 - Change to  ....tide,  led to......

Line 39 - Change to  ....dynamics  control dune.....

Line 44 - Change to  ....of cohesive material....

Line 107 - Change to  ....system was utilized.....

Lines 122-123 - Change to   ....the left/port side of the vessel....

Line 134 - Change to  ...the right/starboard side.....

Line 144-145 - Change to  ...dune. Since elliptical....

Line 185 - Need to define sites where bed samples were collected. (e.g. 1#, 2#, 3#?)

Line 303 - Caption title requires greater detail. Need to say which type of dune is represented by each sub-figure (e.g. a, b, c, d, e, f).

Author Response

Reviewer 2

This is a well written and well reserched contribution which clearly describes the characteristics of Catenary-Bead dunes in the YR. It is good that the conditions which favour the formation of these features are noted.  I think that more detail could be provided about the locations where the sediment sampes were collected (e.g. from a dune or a pit or a combination of both) given this appears to be a significant factor. 

It is noteworthy that the relationships illustrated in Fig 4 are medium to weak (e.g. the red line associated with dry season Dunes) which suggests that other factors may be in play.

[Author’ response]: First, we would like to sincerely thank you for your valuable time in re-reviewing our manuscript. We agree with all your points. In the new version, we have carefully revised the manuscript and the supporting information document according to your constructive comments. Revised contents in the manuscript are highlighted in red fonts in the revised version.

We hope this explanation meets your expectations. Thanks again.

The following minor changes are proposed:

Line 20 - Change to - ....dunes are higher than....

[Author’ response]: Thank you for your suggestion. We have modified this in revised file. Please see line 18.

Line 22 - Change to  ...... types yield a.....

[Author’ response]: Thank you for your help. Revised. Please see line 20.

Line 23 - Change to  ....tide,  led to......

[Author’ response]: Thank you for catching it. We have changed the sentence to: Strong runoff superimposing the ebb tide, led to the development of catenary-bead dunes. Please see line 21.

Line 39 - Change to  ....dynamics control dune.....

[Author’ response]: Thank you for catching it. Modified. Please see line 37.

Line 44 - Change to  ....of cohesive material....

[Author’ response]: Thank you for catching it. Changed.Please see line 42.

Line 107 - Change to  ....system was utilized.....

[Author’ response]: Thank you for your help. We have revised this. Please see line 104.

Lines 122-123 - Change to   ....the left/port side of the vessel....

[Author’ response]: Thank you for your advice. We have modified it.Please see line 120.

Line 134 - Change to  ...the right/starboard side.....

[Author’ response]: Thank you for your suggestion. Modified. Please see line 131.

Line 144-145 - Change to  ...dune. Since elliptical....

[Author’ response]: Thank you for your help. Revised. Please see line 141.

Line 185 - Need to define sites where bed samples were collected. (e.g. 1#, 2#, 3#?)

[Author’ response]: Thank you for catching this. We modified the sample locations in Fig.3a and 3b and added explain in the title: Red circles in Fig.3a and 3b are locations of flow data collection. Black triangles in Fig.3a and 3b are locations of sediment samples. Please see lines 185-186. Meanwhile, we have added the sediment sample method in Method section. Now, The addition is: The surveying vessel was stopped when sampling riverbed sediments. The upper 3-10 cm of the riverbed sediments were collected by a grab sampler[20]. Please see lines 158-160.

Line 303 - Caption title requires greater detail. Need to say which type of dune is represented by each sub-figure (e.g. a, b, c, d, e, f).

[Author’ response]: Thank you for your advice. We have added the detail information about the dune types in the title. Now, the title changed to:

Figure 7. Dune parameters and lee-side slope angle of dunes in the YR Estuary. (a)  catenary-bead dunes with lee-side angle of ~16.7°; (b) and (d) are curved dunes with lee-side angle of ~4.66.5°; (c) and (e) are liner duens with lee-side angle of 5.38°; (f) the catenary dunes with angle of 3.7°. Please see lines 310-313.

Thank you for your valuable time in reviewing our manuscript again. We have do our best to revise our manuscript and hope the changes/additions meet your expectations.