Comparison of Hydrodynamics Simulated by 1D, 2D and 3D Models Focusing on Bed Shear Stresses
Round 1
Reviewer 1 Report
Dear authors,
after reading your interesting paper, I recommend some minor modifications:
Methods
Fig. 1 - add a description why there are some CS marked by circles (should be explained earlier than on l. 347 - ideally in the figure caption)
2.1.1 - 2.1.3 - please add brief information about bed sediment characteristics or additional roughness elements (presented vegetation etc.) - this should reflect your approaches/explanations of model calibration (chapter 3.1, e.g. l. 245-247). See also my second note for the discussion part.
Table 1 - I am not sure if this table (in this form) is really needed. Maybe just express a range of potential values by a single sentence.
Eq.4 - explain B in this equation (I guess that it means channel width)
Table 3 - please explain somewhere in the methods why you used high flow (Q1) only for C.2 and not also for C.3 site (although Q1 R.I. discharge values were mentioned earlier for this site - l. 120). In other words, please add clear information why you performed scenarios presented in Table 3 - in the same way as you explained the selection of study sites (chapter 2.1).
Results
l. 298 - 300 - this is a basic characteristic of simple 1D models and this statement should go to the introduction.
Discussion
- Strickler value issues (l. 440-454) - relationships between the increasing discharge/increasing bed slope and changing Strickler or Manning coefficients are well known from a plenty of laboratory or field experiments- see eg. commentary paper of Fergusson (2010, Earth Surface Processes and Landforms) or papers of Lamb et al. (2008, Journal of Geophysical Research) and Parker et al. (2011, Geomorphology).
- I also think that you can discuss chosen Strickler values at your sites and related potential uncertainties (caused e.g. by heterogeneity of bed sediments and channel units, flow resistance of vegetation) to create a direct link between to the introduction (l. 40-57).
- I would like to see more clearly your opinion/statement in which cases are 1D/2D models suitable/sufficient for prediction of bed shear stresses. Did your study bring some new insight into this issue?
Best wishes, I would be happy to see the paper in press.
Author Response
Thank you for the positive assessment.
Please find the responses to your addressed comments in the uploaded document.
Author Response File: 
Author Response.docx
Reviewer 2 Report
You can use different softwares to simulate one phenomenon. It happens that we get different results from them. Suggestion for further research. Maybe You should repeat the calculations using other computer software.
Author Response
Thank you for the positive assessment.
Please find the response to your addressed comment in the uploaded document.
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Reviewer 3 Report
This manuscript compares the hydrodynamic variables estimated by 1D, 2D, 3D models. The work is nicely written and the results are solid. I think it deserves to be published after a minor revision. I have added a few suggestions and comments for the authors to consider.
(1) The authors did a good job of explaining how the bed shear stress is calculated by 1D, 2D, and 3D models. I think explicitly writing out the governing (continuity and momentum) equations for each of the used models (HEC-RAS, Hydro_AS-2d, and RSim-3D) will provide readers with more insights in their fundamental differences, which can also help understand the results.
(2) Line 22: putting "respectively" in the middle of a sentence looks odd to me. I have more often seen it at the end of a sentence.
(3) Table 1: add an explanation for d90.
(4) Line 187, 194, and 209: the indices need to be corrected.
(5) Line 211: would you please elaborate on how "normal velocities are derived from the given discharge"? And how these boundary conditions were applied in 1D, 2D, and 3D models?
(6) Line 318: it is a little hard to read this (the ratio 3D/1D at high flow conditions) from Figure 5a.
(7) Line 488: could the authors explain or discuss more why almost no differences were present in water surface elevations among models?
(8) Line 491-493: could the authors summarize how these factors cause these differences?
Author Response
Thank you for the positive assessment.
Please find the responses to your addressed comments in the uploaded document.
Author Response File: Author Response.docx
