The Effect of Habitat Structure Boulder Spacing on Near-Bed Shear Stress and Turbulent Events in a Gravel Bed Channel
Round 1
Reviewer 1 Report
The manuscript presents a series of experiments conducted in a laboratory channel. While the topic is interesting, I found many, many, many (I repeated "many" three times to emphasize the number of issues in the manuscript).
Some of them are included below:
Misleading title
Misleading abstract: lab configuration is a 1D array, not a 2D array
Shear stress, by definition, is not a force
Extremely poor English in the Introduction section.
Many basic references are not included in the manuscript (see lines 160, 181 among many others)
Quality of some figures is low. Also, the contour plots should not be straight lines....
Some references are incomplete in the reference section
Author Response
The manuscript presents a series of experiments conducted in a laboratory channel. While the topic is interesting, I found many, many, many (I repeated "many" three times to emphasize the number of issues in the manuscript).
The authors would like to thank the Reviewer for his/her interest and carefully reviewing the manuscript and giving comments/recommendations. We have carefully gone over the manuscript and incorporated these suggestions into the revised manuscript. We have responded to the specific comments one by one as below:
Misleading title
Authors have revised the title in the revised manuscript as follows:
“The Effect of Habitat Structure Boulder Spacing on Near-bed Shear Stress and Turbulent Events in a Gravel Bed Channel”
Misleading abstract: lab configuration is a 1D array, not a 2D array
Authors have added boulder array type in the abstract “…a single array of boulder…”. Moreover, it has been emphasized that this setup consists of a 1D array in a couple of sections, lines 132-133, line 474 of the revised manuscript.
Shear stress, by definition, is not a force
Agree. The shear stress is not a force. The original statement (line 30 of the old manuscript) was misleading. Authors have revised the sentence as “The bed shear stress plays a determinant role in the incipient motion of the sediment.” in line 33 of the revised manuscript.
Extremely poor English in the Introduction section.
The authors have revised the introduction section focusing on the structure of the statement and the grammars. We have also carefully revised the full manuscript with particular attention to language usage from substantial English editing.
Many basic references are not included in the manuscript (see lines 160, 181 among many others)
Authors have added some relevant references in the ADV data treatment (lines 161-183 of the revised manuscript), the quadrant analysis (lines 206-225), and the bed shear stress calculation (lines 184-201) sections.
Quality of some figures is low. Also, the contour plots should not be straight lines....
Authors have re-drawn the Figure 4 to Figure 9 to enhance the quality. The reason behind straight lines in the contour plots is the limited number of the measured points within the detailed measurement zone. To make contour plots smoother, we had to interpolate many points between the measured points. Although this action makes plots smoother, it results in losing accuracy. Therefore, the authors have decided not to change contour plots to keep the results more accurate and reliable.
Some references are incomplete in the reference section
All the references in the bibliography have been checked again. Some incomplete references have been completed e.g., numbers 34, 51, and 62.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
See attached file.
Comments for author File: Comments.pdf
Author Response
The subject studied is very interesting. Although the paper does not provide an advance in current knowledge, however it is a good starting point for understanding how the boulder spacing and boulder submergence ratio affect the near-bed shear stress estimations in stream restoration practices. The results are interpreted appropriately and the most of conclusions are supported by the results. The main weakness of the paper is regarding the measurements of the instantaneous velocities with the ADV. The filtering method used does not seem the most appropriate in a turbulent and aerated flow. This may be one of the main reasons for the low values of R2 . In this regard the authors should review the following references:
- Blanckaert, K. and Lemmin, U. (2006), Means of noise reduction in acoustic turbulence measurements. Journal of Hydraulic Research Vol. 44, No. 1, pp. 3-17.
- Castillo, L.G., (2009). Measurement of velocities and characterization of some parameters inside of free and submerged hydraulic jumps. 33RD International Association of Hydraulic Engineering & Research Congress, IAHR Vancouver, British Columbia, Canada.
- Cea, L.; Puertas, J. and Pena, L. (2007). Velocity measurements on highly turbulent free surface flow using ADV. Exp Fluids. 42:333–348. DOI 10.1007/s00348-006-0237-3.
The authors would like to thank the Reviewer for his/her interest and carefully reviewing the manuscript and for insightful comments and recommendations. We have carefully gone over the manuscript and incorporated these suggestions into the revised manuscript.
The authors are thankful to the reviewer for pointing us the above references.
Studies of Blanckaert and Lemmin (2006), and Cea et al. (2007) were reviewed to review data filtering methods. Unfortunately, method of Blanckaert and Lemmin (2006) was not applicable because a three-beam ADV has been used in this study and the data from the fourth beam are not available (Vectrino, used in this study, only provides data from three beams while Vectrino Plus provides a redundant velocity from the fourth beam that can be used for an additional data noise check). Cea et al. (2007) compared four filtering methods and found that none of them can be considered superior to the others. One of these filters is the phase-space threshold filter which already had been used as a preliminary filter in this study. However, for more clarification, the application of this threshold has been emphasized in the manuscript (lines 164-165). Additionally, Cea et al. (2007) recommended visual inspection of the velocity spectra, an additional check that already had been applied in this study (lines 181-183).
For more clarification, additional information from similar studies have been added to the manuscript to justify the applied filtering scheme in this study (lines 165-173). Therefore, the authors believe filtered data in this study are reliable enough to study the near-bed turbulent flow.
Authors have responded to the specific comments one by one as below:
Figure 6: no boulders (S1-60) indicates that the flow is not symmetrical since there is a concentration of near-bed shear stresses towards the left side of the channel. The authors should clarify this circumstance.
The authors believe that the non-uniform distribution of near-bed shear stress is related to the presence of microforms on the gravel bed in those series of experiments. This non-uniform distribution and its possible reason have been clarified in the manuscript (lines 335-340).
Errors have been detected. Here are some of them as an example:
- Table 1 say: Flor rate (m3 /s)
It should say: Flow rate (L/s)
The authors have replaced ‘m3/s’ with ‘L/s’ in Table 1 in the revised manuscript.
- Line 156 says: Aliased points were despiked aliased according to …
Should be changed by: Aliased points were despiked according to …
The authors have incorporated the suggestion in line 164 of the revised manuscript.
- Line 355 says: Figure 8 and Figure 8 show…
Should be changed by: Figure 8 and Figure 9 show…
The authors have changed ‘Figure 8 and Figure 8’ with “Figure 8 and Figure 9’ in the revised manuscript.
Author Response File: Author Response.pdf
Reviewer 3 Report
This manuscript presents the results of a modeling study that investigates the impact of boulder spacing on bed shear stress in a gravel-bed channel. My main criticism is widespread grammar issues. Sections of the paper are disjointed with grammar errors, including tense issues, missing words, missing punctuation, and awkwardly constructed sentences. The Introduction, especially its first paragraph, suffers from grammar issues and makes it confusing to understand. I indicate a few of the corrections that are needed in the Introduction below. The paper is well organized, but will benefit from copy editing. The science and content of the manuscript is well presented and holds relevance for stream restoration practices.
Line 30: “. . . for the incipient motion of sediment.”
Line 31: “. . . in both hydraulic . . .”
Line 31: I do not understand “prevailing number of the study.” This sentence is awkwardly constructed. There needs to be a better transition to the review of previous work.
Line 43: “. . . shear stress than by the linearly . . .”
Line 45: “. . . acoustic Doppler current profiler (ADCP) . . .”
Line 47: What was found in this field investigation?
Line 48: “The few existing studies measuring the bed shear stress with a disruption . . .”
Line 55: “. . . the effect of a single boulder and a boulder array . . .”
Line 58: “. . . effects of a single boulder . . .”
Line 72: “The Natural . . . “
Line 73: “. . . boulders for channel restoration . . .”
Line 75: “Five stream restoration . . .”
Line 86: “. . . sediment movement, as well as fish behavior and swimming performance, that can . . .”
Line 90: “. . . into the bed region.”
Line 98: So no work is done at a natural stream? Lines 30-31 are especially unclear then, as it implies the study is conducted at both flumes and rivers. The first paragraph of the Introduction needs revision.
Similar errors continue throughout the manuscript.
Author Response
This manuscript presents the results of a modeling study that investigates the impact of boulder spacing on bed shear stress in a gravel-bed channel. My main criticism is widespread grammar issues. Sections of the paper are disjointed with grammar errors, including tense issues, missing words, missing punctuation, and awkwardly constructed sentences. The Introduction, especially its first paragraph, suffers from grammar issues and makes it confusing to understand. I indicate a few of the corrections that are needed in the Introduction below. The paper is well organized, but will benefit from copy editing. The science and content of the manuscript is well presented and holds relevance for stream restoration practices.
The authors are grateful for the Reviewer’s reviewing of this manuscript and giving insightful comments. We have carefully gone over the manuscript and incorporated these suggestions into the revised manuscript. Specifically, manuscript grammar was carefully re-checked and improved.
Authors have responded to the specific comments one by one as below:
Line 30: “. . . for the incipient motion of sediment.”
The authors have revised the sentence as “Bed shear stress plays a determinant role in the incipient motion of sediment.” in line 33 of the revised manuscript.
Line 31: “. . . in both hydraulic . . .”
The authors have incorporated the suggestion in line 34 of the revised manuscript.
Line 31: I do not understand “prevailing number of the study.” This sentence is awkwardly constructed. There needs to be a better transition to the review of previous work.
Authors have revised the sentence with “The majority of the existing studies were conducted in the flumes due to the controlled flow and bed conditions.” in line 34 of the revised manuscript.
Line 43: “. . . shear stress than by the linearly . . .”
The authors have incorporated the suggestion in line 47 of the revised manuscript.
Line 45: “. . . acoustic Doppler current profiler (ADCP) . . .”
The authors have incorporated the suggestion in line 48 of the revised manuscript.
Line 47: What was found in this field investigation?
The authors have deleted the sentence in line 47 of the old manuscript due to irrelevance.
Line 48: “The few existing studies measuring the bed shear stress with a disruption . . .”
The authors have incorporated the suggestion in line 68 of the revised manuscript.
Line 55: “. . . the effect of a single boulder and a boulder array . . .”
The authors have incorporated the suggestion in line 74 of the revised manuscript.
Line 58: “. . . effects of a single boulder . . .”
The authors have deleted the sentence in line 58 of the old manuscript to re-structure the paragraph.
Line 72: “The Natural . . . “
The authors have incorporated the suggestion in line 56 of the revised manuscript.
Line 73: “. . . boulders for channel restoration . . .”
The authors have incorporated the suggestion in line 57 of the revised manuscript.
Line 75: “Five stream restoration . . .”
The authors have incorporated the suggestion in line 59 of the revised manuscript.
Line 86: “. . . sediment movement, as well as fish behavior and swimming performance, that can . . .”
The authors have incorporated the suggestion in line 90 of the revised manuscript.
Line 90: “. . . into the bed region.”
The authors have incorporated the suggestion in line 94 of the revised manuscript.
Line 98: So no work is done at a natural stream? Lines 30-31 are especially unclear then, as it implies the study is conducted at both flumes and rivers. The first paragraph of the Introduction needs revision.
Following the reviewer’s suggestion, authors have revised the first paragraph, in fact, the entire ‘Introduction’ section, focusing on existing methods in literature to estimate near-bed shear stress.
The authors have revised the lines 34-36 of the revised manuscript as “The majority of the existing studies were conducted in the flumes due to the controlled flow and bed conditions. However, the field investigation on the measuring of the bed shear stress is relatively limited.”
Similar errors continue throughout the manuscript.
The authors have carefully revised the text for wording/grammar issues and English language improvement.
Author Response File: Author Response.pdf
Reviewer 4 Report
The present study investigates the effect of boulder spacing and boulder
15 submergence ratio on near-bed shear stress in a gravel bed open channel flume. The article is presented very well and has relevance novelty in the subject matter, and thus can be considered for acceptance.
Author Response
The present study investigates the effect of boulder spacing and boulder submergence ratio on near-bed shear stress in a gravel bed open channel flume. The article is presented very well and has relevance novelty in the subject matter, and thus can be considered for acceptance.
The authors would like to thank the Reviewer for his/her review of this manuscript and for his/her recommendation to accept this paper.
Round 2
Reviewer 1 Report
I appreciate the effort done by the authors. The modified version is in better shape than the original submission.
A couple of things:
Captions in figures 8 and 9 are similar. While the text and the plots indicate different locations...
Too many "the" in the text. Some of them are needed, but not all of them.
Author Response
I appreciate the effort done by the authors. The modified version is in better shape than the original submission.
The authors would like to thank the Reviewer for his/her second time carefully reviewing the manuscript and giving useful comments.
A couple of things:
Captions in figures 8 and 9 are similar. While the text and the plots indicate different locations...
The caption of Figure 9 was corrected.
Too many "the" in the text. Some of them are needed, but not all of them.
We carefully reviewed the paper to correct the grammar issues with a specific focus on the removal of unnecessary “the” in the text.
Reviewer 2 Report
The authors have corrected the main suggestions proposed by the reviewers.
Author Response
The authors would like to thank the Reviewer for his/her second time reviewing the manuscript, much appreciated his/her time.
