COMMENTS TO THE AUTHORS

Title: Terrain visibility impact on the preparation of landslide inventories:

some practical cases

General comments:

This manuscript analysis effects of a visibility of the territory on the quality of landslide inventories. The topic is within the scope of the journal NHESS, important and of scientific interest. The authors provide a review of the literature, including a large number of references. The purpose of the paper is to compare four landslide inventories prepared using different approaches in two study areas of Spain and India. My comment: maybe it would be more correct to compare different methods of landslide inventory for the same area. In other words, you probably need the same number and types of inventories for each of the study regions to compare. My specific comments to the authors are shown below.

Specific comments:

1) The structure of the manuscript is complicated; separate sections contain repeating information. I recommend reorganizing the manuscript as follows: Introduction; Study area; Materials and Methods; Results; Discussion; Conclusion.

2) Sec. 2 Rationale is a part of the literature review and should be combined with the Introduction; repeated sentences in both sections such as, for example, lines 28-30 and 54-57, lines 25 and 64-65, lines 37-38 and 112-114 should be merged / removed.

3) Sec. 3, 5 and 6 should be combined in one Section Materials and Methods (you can divide it into subsections if necessary) and reduced by removing repeated phrases. All the results obtained in the study should be collected in the Results Section and discussed in the Discussion. You can also combine Results with Discussion.

4) Line 123 – Please decipher the abbreviation DTM at the first mention.

5) Line 170 ‑ Figure 2: In the Figure caption, please start with the description of Fig. 2a, and then of 2b (and not vice versa).

6) Fig.2a - On the map, the roads are shown in black, while in the legend they are shown in gray. Please make these designations the same color.

7) Figure 9 is unclear and needs explanations. What is “the landslide size central value”? What is “the median value”? Are these the same terms? What do the dotted lines and horizontal bars mean in the Figure?

8) Line 292 – “Landslides in class 1 are significantly smaller than those included in the other classes” – Why? How can you explain this findings?

9) Lines 293-294 – “Furthermore, the landslide size central value in these two inventories tends to increase with the decrease of the visibility class, while the maximum variation of the median is 188% and 2000% respectively.” I cannot understand this sentence. Please rephrase. Percentage is a fraction of 100. As far as I understand, it cannot be 188 and 2000.

10) Figure 10 ‑ The caption does not match the picture. “The values above each column signify the absolute number of landslides in each visibility class.” - There are no columns in the Figure, no numbers above them.

11) Lines 334-338 - This is a fairly obvious conclusion, understandable initially and without the use of complex mathematical methods.

I believe that the main conclusion from this study may be that the compilation of a landslide inventory requires a combination of both types of methods: remote sensing and field surveys.

General comments

In your work “Terrain visibility impact on the preparation of landslide inventories” your goal is to investigate “a possible relationship between the degree of visibility of the [landslide] territory from roads and the spatial distribution of information on landslides”.

I fear I have to say I do not follow your research question. It is obvious that only visible landslides can be mapped during a field survey, certainly if you do your field survey from a distance. You also explain, and cite, this in your Introduction/Rationale in lines 89-93, even with a comparison to remote sensing products. And you even state you “expected” those results in line 270. As I see it, the present work is basically a validation of your method from a previous work to calculate visibility.

On Introduction/Rationale, in your case, I suggest to not separate Introduction and Rationale. The first part of your Rationale is basically a repetition of the introduction, and on the other hand, the introduction lacks information, for example on what you mean by “visibility”. As stated below, the Rationale can be shortened (see the specific comments). Furthermore, the question of completeness takes a large part in your Rationale (L62-94), but it is not clear how you want to apply this in your work, and indeed you don’t. You only state your goal very briefly in L112-114, this needs to be better connected to what you said before.

The following sections have a fair structure. However, it is often not clear to me, what purpose the content of these serve, i.e. , what is the relation of lithology to your research question? You only briefly state that lithology is homogeneous in your visibility classes in your discussion.

Specific comments

L44-47: This structural information is unnecessary, since it basically just states the headings of the following sections.

L49-52 : You shouldn’t number your listing if you never refer to it again. Furthermore, as stated above, this is a repetition of the part in the introduction on why landslide inventories are important and for what they are used.

L95-111: I don’t see how the meticulous listing of different methods on evaluating the completeness of landslide inventories is relevant for your work. Even more so, since you never bring it up again

L385:  Here you generalize your findings to field surveys and even historical data as a whole, this does not follow, since you limited your investigation to field surveys “from roads”.

Technical corrections

Bracketed citations should be at the end of a sentence not in the middle, if you need to refer to specific works within a sentence use in-text citation.