Main Ethiopian Rift landslides formed in contrasting geological settings and climatic conditions

Martínek, Karel; Verner, Kryštof; Hroch, Tomáš; Megerssa, Leta A.; Kopačková, Veronika; Buriánek, David; Muluneh, Ameha; Kalinová, Radka; Yakob, Miheret; Kassa, Muluken

doi:https://doi.org/10.5194/nhess-21-3465-2021

Articles | Volume 21, issue 11

https://doi.org/10.5194/nhess-21-3465-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/nhess-21-3465-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 21, issue 11

Research article

|

16 Nov 2021

Research article |

| 16 Nov 2021

Main Ethiopian Rift landslides formed in contrasting geological settings and climatic conditions

Karel Martínek, Kryštof Verner, Tomáš Hroch, Leta A. Megerssa, Veronika Kopačková, David Buriánek, Ameha Muluneh, Radka Kalinová, Miheret Yakob, and Muluken Kassa

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Final revised paper (published on 16 Nov 2021)
Preprint (discussion started on 18 Jan 2021)

Interactive discussion

Status: closed

RC1:
'Comment on nhess-2020-420', Anonymous Referee #1, 03 Feb 2021

This paper is focused on the study of landslides in the Main Ethiopian Rift. In particular, this study evaluates the influence of several predisposing factors (tectonics, lithology, geomorphology, and climate) on landslide formation. A very interesting statistical analysis has been performed in two test areas (Arba Minch and Mejo).

I found this paper well-written and clear. The manuscript is well organized and interesting.

I have only few question/suggestions listed below:

In section 2.2 There are several toponyms. It could be helpful to report them in a map.

Figure 1: please report from where the digital elevation model has been obtained and its resolution.

Why did you chosen to remove all the boundaries between lithologies? Sometimes landslide slip surfaces can occur along boundaries between different lithologies.

Figure 3 in not so easy to read. There are similar colours in among passes, ridges and channels. Please try a better way to shoe your results.

Figure 8 is a niche way to show the statistic results but considering the whole area it seems that all the considered factors have the same importance. Please clarify this point.

Please add the Gambelto and Genale rivers in figure 9.

In the discussion section, please, try to justify why precipitation is not an important factor for rockfall formation.

Citation: https://doi.org/10.5194/nhess-2020-420-RC1
- AC1: 'Reply on RC1', Karel Martínek, 13 Apr 2021
  
  Anonymous Referee #1
  
  RC: In section 2.2 There are several toponyms. It could be helpful to report them in a map.
  AC: OK, I will put them to Figs 1, 2, 4.
  
  RC: Figure 1: please report from where the digital elevation model has been obtained and its resolution.
  AC: We were using AsterDEM and SRTM3 (its noted in Methods section) with resolution 30 m. I will add this info also in fig. caption.
  
  RC: Why did you chosen to remove all the boundaries between lithologies? Sometimes landslide slip surfaces can occur along boundaries between different lithologies.
  AC: Yes, you are right, but in our case, the study area is highly weathered and rock properties and susceptibility to land sliding are more dependent on altitude, weather and rock age rather than lithology, which is similar across the area – volcanics and volcaniclastics. I put more info in the text.
  
  RC: Figure 3 in not so easy to read. There are similar colours in among passes, ridges and channels. Please try a better way to shoe your results.
  AC: OK, I will ask co-author to find better symbology.
  
  RC: Figure 8 is a niche way to show the statistic results but considering the whole area it seems that all the considered factors have the same importance. Please clarify this point.
  AC: The diagram is showing the mean values of particular factors occurring across landslides and rockfalls polygons normalized to the mean value for the whole area. So because of normalization, the whole area values are constant. Maybe its confusing to show the column with whole area (it has no information value, it is here just for better understanding how rockfall and landslide values were calculated), I will rather omit it from diagram.
  
  RC: Please add the Gambelto and Genale rivers in figure 9.
  AC: OK, I will.
  
  RC: In the discussion section, please, try to justify why precipitation is not an important factor for rockfall formation.
  
  AC: Its result of our statistical analysis, the precipitation values are virtually the same in rockfall areas as average for whole study area, no anomalies, no extremes as in the case of landslides (they have higher values of all precipitation parameters comparing to average whole area). Frankly speaking we are not 100 percent sure why, probably rockfalls are limited to very narrow areas along upper parts of fault escarpments, typically few hundreds of meters wide, its definitely major controlling factor. Also the resolution of climatic data is very poor, meteorological stations are often many tens of kilometers apart, so interpolation of grid can include in many case cases more mathematics than real world precipitation. Also spatial resolution is poor, no one station has continuous data longer than 10 yrs, there are many gaps in dataset. I will add more explanation to the discussion.
  
  Thank you very much for your time and valuable comments.
  
  Karel Martinek
  
  Citation: https://doi.org/10.5194/nhess-2020-420-AC1
RC2:
'Comment on nhess-2020-420', Anonymous Referee #2, 08 Feb 2021

Dear authors,

I believe that your work was time-consuming, the quality of Figs. is good according to my opinion, nevertheless the text needs to be rewritten significantly. See my comments in the enclosure, please. The main problem is that you have there several statements which are not relevant, and you lowered significantly the potential scientific value of the paper. Chapters are written with different quality, possibly due to a large number of contributors, but at the end one person should do the redaction and avoid statement which are in contrary. The problem might be also in the scale. I suggest you work in a detailed scale, that you can be sure about the relation "cause - response". Several statements are strange to me.

I hope that you will be able to improve the paper. best regards, reviewer

Citation: https://doi.org/10.5194/nhess-2020-420-RC2
- AC2: 'Reply on RC2', Karel Martínek, 13 Apr 2021
  
  Anonymous Referee #2
  RC: in enclosed PDF
  AC: in enclosed PDF
  
  Thank you very much for your time and very valuable comments. I am ready to make thorough editation of text to make it more coherent.
  
  Karel Martinek
  
  Citation: https://doi.org/10.5194/nhess-2020-420-AC2

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

ED: Reconsider after major revisions (further review by editor and referees) (05 Jul 2021) by Filippo Catani

dear Authors

after seeing the reviewers' comments I had to personally review your manuscript myself because of contrasting views on it. This took longer than expected. Sorry about that.
As a result, I think that the paper has potential interest and it is already in an acceptable form for about 60% of its content. It requires, however, some reworking in the remaining part, as suggested by one of the reviewers (see their comments one by one).
In general, you should try to address the following points:

1. Structure of the manuscript: there are intermixed topics where e.g. state-of-the-art portions are provided in the results section as well as others where discussion and results are mixed. Please revise all this throughout the whole document.

2. Methodology is somewhat complex and unclear. Please rewrite and separate into separate sub-sections

3. The statistics and geostatistics parts are not well introduced and justified. Some of the results are interpreted and should be supported. Several statements are in contrast between different sections (see detailed reports by the reviewers). Please fix this.

4. The discussion and the conclusion of your work, which seems to be mainly focusing on landslides, should be more detailed as to which concerns the slope processes themselves. Therefore, the manuscript could improve significantly if you would try to better link methods (specifically statistical) and discussion. For example, when you report possible correlations (or lack of them) among environmental factors and landslides, please try to highlight and support your statements with your provided results. Also on this, please see detailed comments in the reviewers' reports.

Please also reply to all the remaining minor comments and requests of the referees, by providing a one-to-one reply on a separate document and by providing the modified manuscript.

I am sure that, after your modification, the paper could come out in an acceptable form.

Thank you for submitting to NHESS and my apologies again for the delayed review,

best regards
FC

Hide

AR by Karel Martínek on behalf of the Authors (20 Sep 2021) Author's tracked changes Manuscript

EF by Vitaly Muravyev (21 Sep 2021) Author's response

ED: Publish subject to technical corrections (07 Oct 2021) by Filippo Catani

AR by Karel Martínek on behalf of the Authors (15 Oct 2021) Author's response Manuscript

Short summary

This study combines field geological and geohazard mapping with remote sensing data. Geostatistical analysis evaluated precipitation, land use, vegetation density, rock mass strength, and tectonics. Contrasting tectonic and climatic setting of the Main Ethiopian Rift and uplifted Ethiopian Plateau have major impacts on the distribution of landslides.