Constructing Rainfall Threshold for Debris Flows of a Defined Hazardous Magnitude

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors constructed rainfall thresholds for debris flows by combining the TRIGRS model and MassFlow model. The manuscript is interesting and well-written. However, the models have not been well verified in the study area, leading to high uncertainty in the final estimates. Thus, I recommend major revision. Several comments may be helpful to further enhance the quality of manuscript.

 

1. “Debris flow can cause damage only when its discharge exceeds the drainage capacity of the prevention engineering.” is not correct. Because even if the discharge is not so large but with suitable source materials, DF can also occur. 

2. Since the channel topography changes after each event, how can the method well predict the DF with the past fixed rainfall thresholds?

3. Overestimation of landslides in TRIGRS is very obvous. Such uncertainty will be transfered to mass flow modeling. How can the final I-D aviod from the impacts of the uncertainty?

4. Some key parameters of MASSFLOW in the study area should be given. 

5. In Figure 2, the horizontal axis tick labels are prone to confusion with the bar chart and coordinate ticks. It is recommended to remove the coordinate ticks or align them with the bar chart for clarity.

6. Line 254: The author mentioned in a single sentence that you determined the initial material volume using the TRIGRS model. Please provide a detailed description to show how it was estimated.

7. Line 277: The optimally determined parameters should be described in the text rather than merely presented in Table 3. 

8. The values of parameters in Equations 7 and 8 should also be specified within the text.

9. Lines 308: Why do authors calculate them again based on the accumulation volume and soil depth?

10. In Figure 10, "Beloe Condition" should be "Below Condition".

Comments on the Quality of English Language

Some sentences should be cheaked more carefully.

Author Response

请参阅附件。

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The paper presents a methodology for calculating rainfall thresholds based on defined debris flow magnitudes likely to cause damage. The method combines a slope stability model with a fluid dynamics simulation model. Firstly, slope stability is analyzed under varying rainfall conditions to identify unstable areas. Then, the movement and deposition of unstable slope units are simulated to replicate an occurred event. Finally, a rainfall threshold is determined by analyzing conditions causing debris flows of similar magnitude. I appreciate the efforts made by the authors. However, I believe the manuscript needs minor to moderate revisions before being published.

I have provided comments throughout the PDF attached to this review. Here are the major comments summarized:

1.      The text is readable, but the English could be improved with the assistance of a native speaker.

2.      Most of the figures are blurry.

3.      Regarding the reproduction of the real event, I did not understand why you used the average intensity instead of the recorded hyetograph.

4.      Please provide a more extensive comparison between the actual event and the simulation results

5.      Discussions lack content, mainly focusing on the comparison of different ID thresholds:

a.      There is no discussion about the simulation models and the parameters used, in comparison with other works.

 

b.      It might be interesting to see what happens at the confluence with the Bailong River if the number of unstable cells is lower. Is ~40,000 the minimum number required for conditions similar to those observed in 2020, or could something similar happen with a lower number? And if so, how would it affect the set ID threshold?

Comments for author File: Comments.pdf

Comments on the Quality of English Language

The text is readable but the English form should be improved

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

Dear Authors, the proposed research turns out to be very interesting, as often those who work in the field, even in experimental areas have the opportunity to verify various aspects even over longer periods of observation. On the other hand, where data are scarce, the working hypotheses do not always offer guarantees that the debris flow behavior model can adhere to the actual unstable conditions of the debris supply basin.
However, the paper needs additions in the references (about 10 are suggested below, but there are many more that would lead to further study of what other authors have done). Some inaccuracies or observations are given below:
1) km instead of Km in the graphical scale of Figure 1;
nothing is said about historical or recent debris flows in the same watersheds;
2) it is not known whether shallow landslides contribute what percentage to feeding debris flows;
3) in many studies (even those indicated to be cited) rainfall intensities are examined on much shorter time scales, down to 1-5mm/5 minutes. Different rainfall data are available; what are the characteristics of the rainfall that the basin usually receives?

References to cite

1)      https://link.springer.com/article/10.1023/B:NHAZ.0000024897.71471.f2

2)      https://doi.org/10.3390/rs13234813

3)      doi: 10.1029/2012JF002367

4)      https://doi.org/10.3390/w11091915

5)      DOI:10.1007/s12665-012-1985-4

6)      https://nhess.copernicus.org/articles/21/87/2021/

7)      https://www.scirp.org/html/5-1211343_97916.htm

8)   https://doi.org/10.1016/j.geomorph.2022.108557

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

I always question the reliability of the method by combining TRIGRS and MassFlow. As well, coupling is not an appropriate verb to show the relation between the two models.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

Dear Authors,

Thank you for the additions made to the text, which is now much more appreciable.

Best Regards

Author Response

Thank you for your suggestions and comments on this article.