Roads and landslides in Nepal: how development  affects environmental risk

McAdoo, Brian G.; Quak, Michelle; Gnyawali, Kaushal R.; Adhikari, Basanta R.; Devkota, Sanjaya; Rajbhandari, Purna Lal; Sudmeier-Rieux, Karen

doi:https://doi.org/10.5194/nhess-18-3203-2018

Articles | Volume 18, issue 12

https://doi.org/10.5194/nhess-18-3203-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue:

Landslide–transport network interactions

https://doi.org/10.5194/nhess-18-3203-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 18, issue 12

Research article

|

30 Nov 2018

Research article |

| 30 Nov 2018

Roads and landslides in Nepal: how development affects environmental risk

Brian G. McAdoo, Michelle Quak, Kaushal R. Gnyawali, Basanta R. Adhikari, Sanjaya Devkota, Purna Lal Rajbhandari, and Karen Sudmeier-Rieux

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Final revised paper (published on 30 Nov 2018)
Preprint (discussion started on 22 Jan 2018)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'review comments', Anonymous Referee #1, 30 Jan 2018
- AC1: 'Response to Reviewer 1', Brian G McAdoo, 16 May 2018
RC2: 'Review of Brief communication: Roads and landslides in Nepal: How development affects risk by McAdoo et al. NHESS-2017-461', Anonymous Referee #2, 02 Mar 2018
- AC2: 'Response to Reviewer 2', Brian G McAdoo, 16 May 2018
EC1: 'Editor Response to nhess-2017-461', Faith Taylor, 20 Mar 2018
- AC3: 'Response to Editor, F. Taylor', Brian G McAdoo, 16 May 2018

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Reconsider after major revisions (further review by editor and referees) (01 Jun 2018) by Faith Taylor

AR by Brian G McAdoo on behalf of the Authors (11 Jun 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (12 Jun 2018) by Faith Taylor

RR by Anonymous Referee #2 (18 Jul 2018)

ED: Reconsider after major revisions (further review by editor and referees) (24 Jul 2018) by Faith Taylor

AR by Brian G McAdoo on behalf of the Authors (19 Aug 2018) Manuscript

ED: Referee Nomination & Report Request started (23 Sep 2018) by Faith Taylor

RR by Anonymous Referee #2 (03 Oct 2018)

Suggestions for revision or reasons for rejection

As per my previous comment, I believe Figure 1b should be a standalone figure and needs a legend to indicate the root zone. I am not aware of any similar figures, hence suggesting this should be standalone. It would make the paper more citeable if others can use this figure to describe the processes of landsliding near to roads.

Since writing your paper, Froude and Petley have published a new paper on the topic of landslide fatalities. As you cite Petley et al. (2007) It might be worth referring to this updated paper as it supports your findings.

Line 70. This statement that there has not been a study of landslides and roads in Nepal since 1979 is too definitive. For example, Bhandary et al. (2013), Wagner et al. (1988) and others seem relevant. I suggest changing the text to something like ‘there have been a limited number of studies..’.

Line 83, the term ‘scores’ may not translate well. Change to ‘tens’.

Line 94 ‘we present compelling evidence’. I would remove the word compelling as it is not particularly neutral or scientific.

Sentence starting on line 109 needs rewording. Roback et al do not investigate differences in distribution of earthquake and rainfall triggered landslides or the influence of human factors. They state that natural drivers appear to influence the distribution of earthquake triggered landslides, but there is no comparison to rainfall triggered landslides, so this is all you should state there.

Paragraph starting line 135. Give some indication of the area (or better still, normalise by area) of each of these soil types.

There are two figures named figure 2.

Line 103. In this paragraph, please briefly state what you constitute to be landslide area and ensure this is consistent for both inventories (e.g., individual landslide polygons containing both source area and run out, or just source area?).

Line 170. What is the log-normal distribution of landslide areas? I see this in the author response but not in the paper before this point, so it feels a little ‘out of the blue’. Landslide areas more typically have been shown to follow a Double Pareto or Inverse Gamma distribution. State what distribution you used for your post-earthquake landslides.

Line 194 the number of landslides is small by comparison... to the earthquake triggered inventory.

Line 194 rather than saying landslides cover a total area, state that the total area of landslides is x. Otherwise this gets confusing about the overall area in which the landslides occurred.

Line 196. Rather than the average, state the median or mode. Landslide areas span many orders of magnitude and are non-normally or symmetrically distributed so the average is not particularly useful.

Line 196. The average area of the rainfall triggered landslides will most likely be higher because this is not a triggered event inventory and includes some older landslides rather than there being any physical reason behind this. Smaller landslides tend to be eroded away more quickly, leaving only the largest area landslides, which affects the distribution. If you plot the probability density distribution of the rainfall triggered landslide areas, you will see that it is most likely shifted towards the right-hand size of the axis (towards larger landslide areas). See Malamud et al. (2004) for further explanation. The simplest solution would be to remove reference to landslide areas here as your results about roads are more interesting.

Figure 4A belongs with Figure 2 (probability density plots) and would be best presented in the same format, which aids in visualising the broad range of landslide areas which span several orders of magnitude. Figure 4B then becomes separate. These figures are not particularly related, so do not belong together.

Figure 4B incremental percentage lines need point makers at each distance to indicate that this is not a continuous distribution. As I understand it, this line is showing the cumulative percentage of landslides within buffer zones, not the raw distances from each landslide to the nearest road.

Lie 259. Remove reference to average landslide sizes. This is most likely a result of sampling rather than process.

Reference list: Please check all references are complete and in the appropriate format.

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ED: Publish subject to minor revisions (review by editor) (03 Oct 2018) by Faith Taylor

AR by Brian G McAdoo on behalf of the Authors (15 Oct 2018)

ED: Publish subject to minor revisions (review by editor) (26 Oct 2018) by Faith Taylor

Dear Brian and co-authors,

Thank you for your revised version of the manuscript NHESS-2017-461. I am satisfied that you have implemented the majority of the reviewer comments and am pleased to accept the paper to publication subject to a small number of revisions. Revisions (a)-(e) below are small, technical revisions. However, I would like to see your revision with regard to comment (f) below before accepting for final publication.

(a) Please check the figure numbering throughout - both for the figures and reference to the figures in-text. At present you have 2 x Figure 2 and refer to a Figure 3b which is not present.

(b) Line 123, sentence starting 'the landslide inventory we used'. Please state which inventory you are referring to (I think it is the pre-earthquake inventory, or perhaps it is both inventories, in which case say this).

(c) Line 126 sentence starting 'the post-earthquake landslide inventory', please add the appropriate reference at the end of this sentence - otherwise in the following figure 2a (actually figure 3a), it is not clear which of these inventories is the one you actually use.

(d) Line 127, sentence 'consists of scars observed'. I think this should be 'scars and deposits' for consistency with the previous statement.

(e) What is currently labelled as Figure 2b. This is not currently referred to in-text (unless this is an issue with figure numbering). Either refer to in text, or possibly remove. I am reading in printed greyscale and it is not possible to distinguish between pre-and post- inventories, so if you are editing the image, I would appreciate you adding texture/stronger colour contrast to Figure 2b.

(f) Sentence starting on line 181. As per previous reviewer comments, the description of the log-normal distribution remains unclear. Please add a sentence explaining how you chose the log-normal distribution. To replicate your results, readers need to know the parameter values used in the log-normal distribution.

I look forward to receiving the revised manuscript.

Kind regards,

Faith

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AR by Brian G McAdoo on behalf of the Authors (02 Nov 2018) Manuscript

ED: Publish as is (09 Nov 2018) by Faith Taylor

AR by Brian G McAdoo on behalf of the Authors (12 Nov 2018) Manuscript

Short summary

Road development in Nepal promises to improve access to markets, education and healthcare, but not without hazardous consequences. Using GIS maps of monsoon-triggered landslides, we show that rural roads are responsible for doubling the number of landslides in one mountainous district. Engineers are seeking sustainable and affordable eco-solutions to help stabilize these roads in order to prevent further loss of life and property as Nepal approaches this next phase in its development.