Dear Authors,

Your manuscript "Application of UAV-SfM photogrammetry and aerial LiDAR to a disastrous flood: multitemporal topographic measurement of a newly formed crevasse splay of the Kinu River, central Japan" (nhess-2017-42) has now been assessed by two reviewers. You have also provided feedback during the NHESS open discussion. Based on this discussion, I would like to inform you that the manuscript is potentially acceptable for publication in NHESS, subject to minor revisions suggested by the reviewers.

Once you have made the necessary corrections, please submit a revised manuscript with a point-by-point response. Also please highlight all changes made when revising the manuscript. Please ensure you include a detailed rebuttal of any criticisms or requested revisions that you disagreed with. Also, ensure that your revised manuscript conforms to the journal style.

Please note that this editorial decision does not guarantee that your manuscript will be accepted for final publication in NHESS. A decision will be made after the revised version is submitted and evaluated by the same or further reviewers.
We look forward to receiving your revised manuscript soon.

Best regards,
yuichi hayakawa

Dear Authors,

Your manuscript "Application of UAV-SfM photogrammetry and aerial LiDAR to a disastrous flood: multitemporal topographic measurement of a newly formed crevasse splay of the Kinu River, central Japan" (nhess-2017-42) has now been assessed by two reviewers. You have also provided feedback during the NHESS open discussion. Based on this discussion, I would like to inform you that the manuscript is potentially acceptable for publication in NHESS, subject to minor revisions suggested by the reviewers.

Once you have made the necessary corrections, please submit a revised manuscript with a point-by-point response. Also please highlight all changes made when revising the manuscript. Please ensure you include a detailed rebuttal of any criticisms or requested revisions that you disagreed with. Also, ensure that your revised manuscript conforms to the journal style.

Please note that this editorial decision does not guarantee that your manuscript will be accepted for final publication in NHESS. A decision will be made after the revised version is submitted and evaluated by the same or further reviewers.
We look forward to receiving your revised manuscript soon.

Best regards,
yuichi hayakawa

Dear Authors,

Thank you for submitting your revised manuscript "Application of UAV-SfM photogrammetry and aerial LiDAR to a disastrous flood: repeated topographic measurement of a newly formed crevasse splay of the Kinu River, central Japan" (nhess-2017-42). The manuscript was considerably revised with point-by-point responses to the reviewers. Yet, there are some minor issues, mostly regarding the language. I have noted several points as below, but it is recommended to check the English of the manuscript thoroughly by some external service or native speakers. The main problem is the frequent occurrence of redundancy with too long sentences.

Please note that this editorial decision does not guarantee that your manuscript will be accepted for final publication in NHESS. A decision will be made after the revised version is submitted and evaluated by the editor.
We look forward to receiving your revised manuscript soon.

Best regards,
yuichi hayakawa

****

Specific comments

Page 1 Lines 15-17 Please make it concise.

Page 1 Lines 22-25, 25-29 Redundant.

Page 2 Lines 11-12 Just “(Gomez and Purdie, 2016)” would be enough.

Page 2 Line 14 Insert “aerial” before “LiDAR”

Page 2 Line 16 Rephrase as "The UAV-based SfM photogrammetric method (UAV-SfM)"

Page 2 Line 18 “gravelly” >> “gravel-bed”

Page 2 Line 18 It seems that the sentences after the second “Although” is not specifically related to the “high-resolution topographic data” but to more general issue in the floodplain studies. Can it be a new paragraph?

Page 2 Lines 25- The sentences can be rephrased as:
"In this study, these difficulties were challenged using high-resolution topographic datasets for the case of a disastrous flood along the Kinu River, central Japan in 2015, which affected an inhabited and cultivated floodplain characterized by the formation of crevasse splay. Three digital surface models (DSMs) of the research area were generated by aerial LiDAR and UAV-SfM: before, 3 days after, and 3 months after the flood.
The features and post-formation modification of thetopography caused by a levee breach were then quantitatively documented from the perspective of both natural and artificial changes. In addition, volume calculation was conducted using these DSMs to investigate the balance between deposition and erosion processes during the flood, and the volumetric extent of the post-flood restoration works in the breached artificial levee and intensively eroded areas.”

Page 3 see the attached file.


Page 4 Lines 17-20 Better to split this long sentence.

Page 4 Line 22-23 “159.2 billion yens in Ibaraki Prefecture” could be unnecessary. “yens” >> “JPY"

Page 4 Lines 24-25 Rephrase and shorten the sentence below, or just remove it because the reference is already cited on Line 17.
"For further information of 2015 flood of the Kinu River, see Nagumo et al. (2016) which have provided a detailed report of damages and social effects in the flooded areas.”

Page 5 Line 3 "fairly accurate” >> "fairly clean to represent the bare land”

Page 5 Line 15 What kind of interpolation method did the authors use?

Page 5 Line 16 Is this RTK-GNSS?

Page 5 Line 17 “internal” >> “inertial”

Page 5 Line 20 What is “APM”?

Page 5 Line 25 "focal length, ” >> “focal length: "

Page 6 Line 3 "west direction, and 1.58 cm” >> "west direction, 1.58 cm”
“0.455” >> “0.46”

Page 6 Line 8 “technics” >> “techniques”

Page 6 Line 15 “gradient” >> “slope gradient"

Page 6 Line 19 “set to the same” >> “set to be the same”

Page 7 Line 14 remove “were” before “no longer”

Page 7 Line 29 “shows” >> “show"

Page 8 Lines 27-31 The sentence below is too long and hard to read.
"Althoughthere were some points which experienced local aggradation or degradation due to similar restoration works as such, thecrevasse splay was left mostly undisturbed, or had little modification so its features were deformed mainly by natural phenomena occurring during the 3 months after the flood, except for the reconstruction of the artificial levee and the landfilling and leveling along the prefectural road near the breached levee.”

Page 12 Line 4 “resolution” >> “horizontal resolution"

Page 13 Lines 1-4 The sentence below is too long and hard to follow. I would recommend to split them. Also, the third point is unclear.
"However, the volume estimation in this study have some issues including (i) effects other than the topography such as buildingsand agricultural crops, (ii) lack of topographic data showing the entire part of the crevasse splay: partly the erosion depthscould not be estimated due to the restoration works, and (iii) ifonly a single process worked at a point, namely, erosion in theaggradational pixels and deposition in the degradational pixels were neglected.”

Page 13 Lines 4-6 For the improvement of volume estimation, the better filtering of the data makes sense, but it is unclear why more frequent measurements contribute. Please explain.

Figure 7 The “dashed line” is unclear to see. Use a different color.

Dear Authors,

Thank you for submitting your revised manuscript "Application of UAV-SfM photogrammetry and aerial LiDAR to a disastrous flood: repeated topographic measurement of a newly formed crevasse splay of the Kinu River, central Japan" (nhess-2017-42). The English of the manuscript was adequately revised. Before being published, some further technical corrections are now required.

1) This is not mandatory, but if applicable, I would recommend describing thanks to the reviewers, as well as to the native English speakers who supported revising the manuscript in Acknowledgements.
See also:
https://www.editage.com/insights/why-should-i-acknowledge-writing-assistance-if-i-have-paid-for-it-a-case-study

2) Page 5 Lines 18-25: "The elevation of the inundated areas was interpolated to a grid in the same way as the non-inundated areas." can be modified to:
"The elevation of the inundated areas was interpolated to a grid in the same way as the non-inundated areas (TIN method).”

3) Page 6 Line 31: "The term has been modified as 'pixel gradient' as it seems to be common. The same term is used in the other parts of the manuscript.”
I am unfamiliar with the term “pixel gradient” as a term representing the slope of topography using DEM (either DSM or DTM). I think “pixel gradient” may fit other types of raster data (RGB etc.), while “slope gradient” directly represents the topographic slope. Also, please clarify what method was used to calculate the gradient (conventional eight cells method?).

4) Page 13 Line 10: "that assumption is not valid.” can be modified to:
"that assumption is not validated."

Please note that this editorial decision does not guarantee that your manuscript will be accepted for final publication in NHESS. A decision will be made after the revised version is submitted and evaluated by the editor.
We look forward to receiving your revised manuscript soon.

Best regards,
yuichi hayakawa