Riverbed Morphologies Induced by Local Scour Processes at Single Spur Dike and Spur Dikes in Cascade
Round 1
Reviewer 1 Report
The present study would like to provide new insights into the spatial and temporal morphological patterns around spur dikes, emphasizing the temporal evolution of the maximum scour depth around (typically at the tip) a single spur dike or dikes in cascade. However, it is within the scope of Water Journal and it needs major revisions before it can be accepted as follows:
1. The English of this manuscript should be reviewed by a native English speaker.
2. Abstract not well organized. It is too long so it should be shortened by focusing by bring out what was missing in the earlier literature. What are the new contribution, motivation, hypothesis, and significant results? It is recommended to use quantitative reasoning.
3. Introduction: It is almost impossible to understand the motivation for conducting this research after reading the Introduction. Clear statements on the motivation behind conducting the research should be mentioned. It needs modifications by new recent literature to show the difference between the current work and the previous one.
Moreover, all equations in the Introduction section should be moved into the reduction data section or another section such as empirical correlations.
4. The main concern I have about the paper is with respect to the contributions of your work. The used methodology has a few outstanding innovation points. So, what innovative work have you done compared with previous studies?
5. How does your work contribute to this field? It is not clearly stated in the abstract and conclusions sections.
6. Section 2 is incomplete where the experimental procedure, instrumentation accuracy and uncertainty analysis are missing. Moreover, a sub-section about the uncertainty analysis should be provided with an uncertainty table for each instrument/tool.
7. The instruments and devices with their uncertainty should be clearly presented.
8. Uncertainty analysis is missing so it should be provided.
9. Data Reduction/processing section should be added after the Uncertainty analysis section.
10. More parametric analysis is required where results are not sufficient and there are some inconsistencies in the results of tables and figures. The present results are limited, so they cannot be published in this journal.
11. The discussion should be connected with real applications and issues related to technology/system nature. The results should be enhanced with more description in the physical approach.
12. The work does not provide a well-written conclusion section in terms of main findings and contributions. The relevance of the work with respect to the applied science aspect should be discussed in the conclusion section. All cited references should be removed from the conclusions section.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The manuscript is the outcome of the experimental study on riverbed morphology due to spur dikes. The results are useful for hydraulic engineers. Following are my suggestions/queries:
1) The introduction shall be more specific.
2) Authors failed to present specific scope of the study.
3) In experimentation, how depth of flow is controlled?
4) As the sediment properties (size and gradation) and dike width are constants, they can be deleted form Table 1.
5) In line 210-211, authors mention about sporadic measurement of velocity. Is it possible to add in the manuscript that will add dimension to the manuscript.
6) What could be the reason for no scour around spur dike 2? Is it due to shadowing effect of spur 1 or scour at 2 is covered by the deposition of sediment flowing from spur 1?
7) What could be the maximum distance between spur dikes 1 and 2 so that the shadowing effect can be eliminated?
8) What is the physical meaning of parameter on y axis in Figure 5and 6, Z0.5/F1.5d? Z being non-dimensional quantity would by more appropriate to show the result.
9) I suggest the plots in Figure 6 be presented with color to enhance the visibility of results. What is the use of confidence limits as 25% confidence limit has no meaning in Figure 6(b)?
10) In Figure 6 (a and b), please change the time scale to 104 to 105 to understand the trend in detail.
11) The conclusions have become more general. Please add results in the conclusions.
12) How is the scour measured? At what point the scour depth is maximum?
13) How did the bed profile is measured, is it by imaging or point gauge measurement?
14) In Figure 4, morphology around dikes 2, 3 and 4 are same for runs IM3, IM5 and IM7. Why it is different at dike 3? Are there any observations?
15) What could be the optimum spacing of spur dike 2 from 1 so that this combination can be used as bank protection instead of cascading dikes? This would reduce the number of dikes and increase efficiency. Please comment.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Reviewer 3 Report
I am interested in this work and hope it can get to be considered again for publication, but only after very carefully addressing the points I am making below.
The manuscript needs to carefully be checked for grammar, use of consistent and precise technical language (for example “turbulences” has no plural, “spurs” should be “spur dikes” ect), throughout. There are some parts that make no sense and need be re-written (eg “Regarding to the approach flow”, “so found out the underestimation.” ect).
The literature review presented is quite traditionally focused but at the same time quite limited (less than 20 references!) and lacking recent references (!) with only one being from the last decade(!). There is a wealth of references the authors can use from the general topic of spur dike scour including for example this recent one:
|
Experimental assessment and prediction of temporal scour depth around a spur dike M Pandey, M Valyrakis, M Qi, A Sharma, AS Lodhi International Journal of Sediment Research 36 (1), 17-28 |
Also there are cases which are not substantiated, indicative of the poor practice in the literature presented (eg see line 146).
The way the literature review is written and structured talks of a low level sequential presentation of past research which may be somewhat tiring for the reader, when it is not clear how this links to the current work. There is a lot of information presented that is entirely out of context (for example see line 85: why does it matter where the lab tests were performed?), and as a result with little focus on the actual novelty of each work cited. One suggestion is to limit any equations presented in the introduction section to only what is essential to establish convincingly the current gap in the literature and any of these that need to be used later on in the analysis and discussion section, can be presented later (perhaps also in a tabular form which will make easier their comparison and reference from the reader).
It is extremely important that the literature satisfies the purpose it is being introduced for. This is to demonstrate that the latest relevant literature of the topic is shown in context with the question this manuscript examines, and then establish clearly the gap in the literature, which this research takes as a mission to cover. This is currently entirely missed and needs to improve significantly.
Then the established gap needs to clearly show how it feeds into shaping the purpose of this manuscript and also that this is novel enough (thus the need of recent topical literature).
The description of experiments, despite seemingly appearing tidy, is lacking in many and important aspects need further clarity as shown in the following.
Can the authors offer more elaboration and proof (eg via more plots taken at a later time) that the equilibrium scour has been reached? If not is it possible that their presented results are relatively conservative and if yes by how much?
Specifically, it is important to discuss technical aspects such as: depth of sediment bed, bed surface elevations upstream and downstream the test section before and after the experiment, if sediment was recirculating or not.
Add more emphasis on the way (methods and tools used, and their accuracy and expected error) the bed surface was surveyed and how these data were used to produce the contour plots demonstrated (eg what type of interpolation and whether it ensures it shows the max scour point). Pay particular attention to showcase the measurement points where max scour is expected and ideally show these on the contour plots.
The authors use “Mild” and “Strong” to classify some of their experiments according to the approach flow conditions. In hydraulics the term “Mild” and “Steep” are used for similar classifications - I am not sure if the authors attempt to refer to the hydraulic regime: if they do then they should demonstrate these are indeed such conditions (also considering mean flow conditions and the change in roughness that the introduction of dikes presents macroscopically) otherwise they should avoid using terms that might be confusing to the reader.
Also if all flows are “impervious” then why include it as a classifier? There is no other mention of the word impervious in the document or explanation as to what it refers to (probably impervious dikes?).
Another issue is with the dikes geometry: no width is considered(?) or mentioned. If it has been considered, how does it scale geometrically with the rest of the flow and bed surface grain size? Does the resulting scaling corresponds to realistic bed surface conditions (or perhaps an armoured bed surface) and is it reasonable to have such a width of a dike? How would the results might be different if a different width was considered?
In Fig. 1 the distance of the 7th dike should be shorter than 3b from the dash-dotted lines.
In Fig.2 the authors should mention if these tracers are buoyant or not. If yes then clarify that these are surface flow structures and attempt establishing a connection to the bed surface effects studied here (scour).
What is the physical explanation for the scour patterns observed? Why is there no more discussion of the second dike not having as much scour as the third (which is a different trend to what is being discussed)?
This discussion would be useful in allowing the reader to understand how the results might generalise eg for different distances of the dikes and perhaps the need of considering a flow dimension to attempt a dynamic non-dimensionalisation of the results.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
All the suggestions are incorporated in the revised manuscript. I accept the manuscript in the present form.
Reviewer 3 Report
I would like to thank and congratulate the authors for addressing this reviewer’s remarks satisfactorily.
