Using the Spatiotemporal Hot Spot Analysis and Multi-Annual Landslide Inventories to Analyze the Evolution and Characteristic of Rainfall-Induced Landslide at the Subwatershed Scale in Taiwan
Round 1
Reviewer 1 Report
In my estimation the paper contains valuable data and the performed research seems interesting to the reader. The topic is an up-to-date reference to a very hazardous phenomenon , espacially in the region of the world that is very prone to landslides. The concept and assumptions are thought to follow contemporary research needs to better understand and prevent dangerous movement of the rock or soil. As far as I am concerned, it is a real effort of the authors to search for proper analytical methods to solve the research questions and provide for scientific novelty. Even if the overall idea and structure is considered to be appropriate, the presented study unfortunately failed to contribute to the state of the art in the field of landslide mapping and prevantion. The subject is interesting and falls within the contemporary, relative research field, but what is the real advance of this work from the scientific point of view. I would rather select two or three case studies, if possible, and show in details the soil particle size (grain) distribution, the type of the soil , the particular spot- the hillside, river valley etc. to portray the underlaying mechanisms. It deserves to be explained, what is the meaning of ,,hot spot” evaluation and detection ? Is it included into a set of GIS methods/prcedures? A known one?
Line 68-107 : the suggested methods need to be supplemented and refined. It is with regret , but the adpoted methodology rather be standard.
Line 125- general characteristics of particle (grain) size composition would better show the base of the study.
Line 174-185 – what is the definition of the ,,cube”? Is it a particular geometry of the slide/slip surface? Do you analyse, anyway, the geometry or volume of the lanslide? Of the soil being swept away?
The methods, as stated above, would need more description. Otherwise, it might be difficult to grasp things, to comprehend them. What is more, there may objection to the case as local- only one country /region. What is the assumtion/procedure for landslide inventory? From satellite imagery?
To the best of my belief, it is a particular study of an impotance, to acknowledge a vital problem, but the,, essence” is missing. The submitted manuscript , respectfully, would require taking more scientific shape, and justification, what kind of problem of a more global conern is to be solved.
Author Response
Dear Water journal and all reviewers,
My sincere appreciation for the valuable comments from all reviewers. The responses for all comments are listed in the following sentences.
Chunhung WU
***
Response for Reviewer 1 comments
Comment: Even if the overall idea and structure is considered to be appropriate, the presented study unfortunately failed to contribute to the state of the art in the field of landslide mapping and prevantion.
Response: My appreciation for your comments. The purpose of this study focuses on explaining the long-term evolution characteristic of landslide which was induced by extreme rainfall events by using the spatiotemporal hotspot analysis technology. Knowing the long-term evolution characteristic of landslide can contribute to plan the correct engineering in the correct place to prevent the secondary geological hazard. The Fig. 10 in this study, for example, showed that controlling the sediment transport in the rivers of upstream watershed was the first priority in helping the watershed recovery. Furthermore, the spatiotemporal hotspot analysis technology proposes 16 characteristic of spatiotemporal hotspot, and this also help readers and researcher to understand the temporal characteristic of landslide evolution.
The revision based on this comment had been added in line 95-100 in the revised manuscript.
Comment: I would rather select two or three case studies, if possible, and show in details the soil particle size (grain) distribution, the type of the soil , the particular spot- the hillside, river valley etc. to portray the underlaying mechanisms.
Response: My appreciation for your comments. We don’t have detailed soil grain data or soil particle size distribution in whole Taiwan, but we do have some comparison of soil properties before and after 2009 Typhoon Morakor in the Kaoping river watershed, southern Taiwan. The Kaoping river watershed was of the most serious landslide disaster after 2009 Typhoon Morakot in Taiwan.
Most landslide concentrated in the central and southern Taiwan, especially in the central mountain region. The extreme rainfall during 2009 Typhoon Morakot resulted in serious landslide disaster in the central and southern Taiwan. Most landslide induced by 2009 Typhoon Morakor concentrated in five landslide-prone stratigraphical formations, including the Changchihkeng Formation, Chaochou Formation, Pilushan Formation, Lushan Formation, and Tayuling Formation. The occupied percentage of the five landslide-prone stratigraphical formations in Taiwan is < 30%, but the landslide area within the five landslide-prone stratigraphical formations occupied > 70% of the all landslide area after 2009 Typhoon Morakot in Taiwan. The main composition in the five landslide-prone stratigraphical formations are sandstone, shale and slate.
Based on the comparison of soil properties in Kaoping river watershed before and after 2009 Typhoon Morakot, most sediment yield from landslide during 2009 Typhoon Morakot was deposited in the down hillslope or transported into the rivers, especially in the upstream watersheds. But the fine sediment in the sediment deposition in the down hillslope or in the river bed had gradually transported to the downstream after several heavy or flooding events after 2009 Typhoon Morakot. The composition of sediment deposition in the down hillslope or in the river became coarse. The coarse sediment deposition in the river also became the armor layer.
We had added some explanation of the comparison of soil properties before and after 2009 Typhoon Morakot in the revised manuscript. The revision based on this comment had been added in line 138-146 in the revised manuscript.
Reference
Tsai, S.R. Spatial variation of soil properties in Kaoping river basin prior and post typhoon Morakot. Master Thesis. National Pingtung University of Science and Technology 2011, P52.
Comment: It deserves to be explained, what is the meaning of ,,hot spot” evaluation and detection ? Is it included into a set of GIS methods/prcedures? A known one?
Response: My appreciation for your comments. We had added more explanation to explain how to build the spatiotemporal landslide cube models, how to use the Mann-Kendall statistic to detect the temporal trend of landslide ratio, and how to use the Anselin Local Moran’s I index to detect the spatial trend of landslide ratio in the spatiotemporal landslide cube models in the Supplementary Materials and the revised manuscript.
The revision based on this comment had been added in line 169-171, 202-203, 207-209, 217-223, 234-238 in the revised manuscript and the “4. The spatiotemporal landslide cube model” and “5. Detect or measure the temporal and spatial trend of landslide ratio in the spatiotemporal landslide cube model” in the Supplementary Materials.
Comment: Line 68-107 : the suggested methods need to be supplemented and refined. It is with regret , but the adpoted methodology rather be standard.
Response: My appreciation for your comments. We had added more explanation to explain how to build the spatiotemporal landslide cube models, how to use the Mann-Kendall statistic to detect the temporal trend of landslide ratio, and how to use the Anselin Local Moran’s I index to detect the spatial trend of landslide ratio in the spatiotemporal landslide cube models in the Supplementary Materials and the revised manuscript.
The revision based on this comment had been added in line 202-203, 207-209, 217-223, 234-238 in the revised manuscript and the “4. The spatiotemporal landslide cube model” and “5. Detect or measure the temporal and spatial trend of landslide ratio in the spatiotemporal landslide cube model” in the Supplementary Materials.
Comment: Line 125- general characteristics of particle (grain) size composition would better show the base of the study.
Response: My appreciation for your comments. The comments had been replied in the above response (the second response). We had added some explanation of the comparison of soil properties before and after 2009 Typhoon Morakot in the revised manuscript. The revision based on this comment had been added in line 138-146 in the revised manuscript.
Comment: Line 174-185 – what is the definition of the ,,cube”? Is it a particular geometry of the slide/slip surface? Do you analyse, anyway, the geometry or volume of the lanslide? Of the soil being swept away?
Response: My appreciation for your comments. The spatiotemporal landslide cube model had been explained in detail in the “4. The spatiotemporal landslide cube model” in the Supplementary Materials. The word “cube” in this study was used to describe the three dimensional landslide models, including spatial data and temporal data.
The revision based on this comment had been added in line 202-203 in the revised manuscript and the “4. The spatiotemporal landslide cube model” in the Supplementary Materials.
Comment: The methods, as stated above, would need more description.
Response: My appreciation for your comments. We had added more explanation to explain how to build the spatiotemporal landslide cube models, how to use the Mann-Kendall statistic to detect the temporal trend of landslide ratio, and how to use the Anselin Local Moran’s I index to detect the spatial trend of landslide ratio in the spatiotemporal landslide cube models in the Supplementary Materials and the revised manuscript.
The revision based on this comment had been added in line 202-203, 207-209, 217-223, 234-238 in the revised manuscript and the “4. The spatiotemporal landslide cube model” and “5. Detect or measure the temporal and spatial trend of landslide ratio in the spatiotemporal landslide cube model” in the Supplementary Materials.
Comment: What is more, there may objection to the case as local- only one country /region.
Response: My appreciation for your comments. We show the hotspot distribution in all subwatershed scale in Taiwan and in a single subwatershed scale in this study. Spatiotemporal hotspot distribution in all subwatershed scale can show the long-term evolution of landslide and the relationship between landslide and geological setting in Taiwan. Spatiotemporal hotspot distribution in a single subwatershed scale can show the long-term landslide evolution in the rivers and hillslope. We hope to show the spatiotemporal hotspot distribution in the two scale to provide different information to readers.
Comment: What is the assumtion/procedure for landslide inventory? From satellite imagery?
Response: My appreciation for your comments. We had added more explanation of the production process of the annual landslide inventories in 2003-2017 in Taiwan in the revised manuscript and Supplementary Materials.
The revision based on this comment had been added in line 169-171 in the revised manuscript and the “3. The annual landslide inventories in 2003-2017 in Taiwan” in the Supplementary Materials.
Comment: To the best of my belief, it is a particular study of an impotance, to acknowledge a vital problem, but the,, essence” is missing. The submitted manuscript , respectfully, would require taking more scientific shape, and justification, what kind of problem of a more global conern is to be solved.
Response: My appreciation for your comments. The essence in this study is to introduce a new analysis technology to explore the characteristic of long-term landslide evolution. The spatiotemporal hotspot analysis is a new analysis method and less (or even rarely) used in long-term landslide evolution research field in published papers. We believed that any new analysis technology which was introduced to the landslide research field should have the scientific meanings or academic significance. The findings of our research can be referred or used in other countries where had faced the serious landslide disaster in the past few years, like the serious landslide disaster caused by the heavy rainfall events in July, 2020 in southern Japan, including Kumamoto, Nagano, and Kagoshima Prefectures.
We add the advantages of using the spatiotemporal hotspot analysis method to analyze the long-term landslide evolution in line 518-526 in the revised manuscript.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Title
The Title reflects the paper’s content accurately.
Abstract
The Abstract determines the paper’s content and objectives in a very manifest and complete fashion.
1. Introduction
In L30 add that rainfall variability under present and future climate is examined as a function of global warming (Panagoulia et al., 2006), the trend of extreme rainfall events has been rising during the last three decades (Hayley J. Fowler & Haider Ali, 2022) and that flood events are sensitive to global climate changes (Panagoulia & Dimou, 1997).
Otherwise, the Introduction is quite adequate and highly informative.
2. Study Area
Quite well written.
3. Materials and Method
Well supported and exhaustive.
4. Results
Well written and in causal connection with previous sections.
5. Discussions
Well written and based on material examined.
6. Conclusion
An excellent summary.
References
Hayley J. Fowler, & Haider Ali. (2022). Analysis of extreme rainfall events under the climatic change. In Renato Morbidelli (Ed.), Rainfall Modeling, Measurement and Applications (1rst ed., pp. 307–326). Elsevier.
Panagoulia, D., Bárdossy, A., & Lourmas, G. (2006). Diagnostic statistics of daily rainfall variability in an evolving climate. In Advances in Geosciences (Vol. 7).
Panagoulia, D., & Dimou, G. (1997). Sensitivity of flood events to global climate change. Journal of Hydrology, 191, 208–222.
Author Response
Dear Water journal and all reviewers,
My sincere appreciation for the valuable comments from all reviewers. The responses for all comments are listed in the following sentences.
Chunhung WU
***
Response for Reviewer 2 comments
Comment: In L30 add that rainfall variability under present and future climate is examined as a function of global warming (Panagoulia et al., 2006), the trend of extreme rainfall events has been rising during the last three decades (Hayley J. Fowler & Haider Ali, 2022) and that flood events are sensitive to global climate changes (Panagoulia & Dimou, 1997).
Response: My appreciation for your comments. The sentence had been added in line 29-31 in the revised manuscript.
Author Response File: Author Response.docx
Reviewer 3 Report
This article is very well done, well structured and answers the jounal's theme.
However I advise the author to rectify the comments that I presented throughout this article, then to update them.
Comments for author File: 
Comments.pdf
Author Response
Dear Water journal and all reviewers,
My sincere appreciation for the valuable comments from all reviewers. The responses for all comments are listed in the following sentences.
Chunhung WU
***
Response for Reviewer 3 comments
Comment: Rephrase alphabetically the keywords.
Response: My appreciation for your comments. The keywords had been rephrased alphabetically in the revised manuscript.
The revision based on this comment had been added in line 25-28 in the revised manuscript.
Comment: The conclusions are too weak. How they are now I cannot see how it contributes to the advance of the thematic field. In this regard, other researches and studies should be exposed, confronted/compared to create a discussion in order to enrich the state-of-the-art and consequently further develop the field.
New references:
- Lousada, S.; Cabezas, J.; Castanho, R.A.; Gómez, J.M.N. Hydraulic Planning in Insular Urban Territories: The Case of Madeira Is-land—Ribeira Brava. Water 2021, 13, 2951, doi:10.3390/w13212951.
- Lousada, S.; Gonçalves, L.; Atmaca, A. Hydraulic Planning in Insular Urban Territories: The Case of Madeira Island—São Vicente. Water 2022, 14, 112, doi:10.3390/w14010112.
- Lousada, S.; Castanho, R.A. GIS-Based Assessment of Morphological and Hydrological Parameters of Ribeira Dos Socorridos and Ribeira Do Vigario Basins, Madeira Island, Portugal. Curr. World Environ. 2021, 16, 408–426, doi:10.12944/CWE.16.2.08.
- Lousada, S.A.N.; Moura, A.D.S.; Gonçalves, L.B. Numerical modelling of the flow rate in artificial water channels: application to Ribeira Brava´s stream. Rev. Bras. Planej. E Desenvolv. 2020, 9, 39–59, doi:10.3895/rbpd.v9n1.10974.
- Lousada, S.; Cabezas, J.; Castanho, R.A.; Gómez, J.M.N. Land-Use Changes in Insular Urban Territories: A Retrospective Analysis from 1990 to 2018. The Case of Madeira Island—Ribeira Brava. Sustainability 2022, 14, 16839, doi:10.3390/su142416839.
Response: My appreciation for your comments. We had revised the discussion in the revised manuscript.
The revision based on this comment had been added in line 526-533 in the revised manuscript.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
I would like to thank the Authors for providing detailed comments and the revised version of the manuscript. I expect the paper to be processed further and be published along with supplementary materials, as they give more explanation to the problems being analysed.
