Comment on esurf-2021-62

We are very grateful for your help with the manuscript entitled “Failure mode of rainfallinduced landslide of granite residual soil, southeastern Guangxi province, China”. Your valuable comments effectively improve the quality of the paper. We have carefully revised the manuscript following your detailed comments and proofread the content to remove mistakes about grammar and spelling in real earnest.

In section 2.2, the authors selected two dry densities (1.2 g cm -3 and 1.4 g cm -3 ). Why two dry densities (1.2 g cm -3 and 1.4 g cm -3 ) are selected? Why does the test not consider 1.3 g cm -3 ? Please explain it.
Authors' response: Thanks a lot for your comment. The detailed field investigation shows that the granite residual soil landslide in the study area is mainly shallow, and the dry density of the soil is 1.2 ~ 1.4 g cm -3 (Wen, 2015). If 1.3 g cm -3 is considered in this paper, there is a difference of 0.1 g cm -3 between the initial dry densities. At this time, the difference in the mass of each layer of soil will be 5 kg, and the difference in the total mass of the model slope will be less than 30 kg. This small difference in soil mass can cause the test results to be similar, and may even be unfavorable for the author to identify the influence of initial dry density on the landslide formation. Therefore, in order to highlight the differences in test results, only two dry densities (1.2 g cm -3 and 1.4 g cm -3 ) are selected in this paper. The explanation has been added in this paper, it can be found in Line 132-135.
The size of Figure 5(b) should be normalized. The unit of model size and soil depth should be consistent in the paper.
Authors' response: Thank you for your comment. The unit of model size and soil depth in Figure 5(b) has been modified to meters. The revised details can be found in Line 171-172. Furthermore, the unit of model size and soil depth throughout the paper has been unified as meters.
There are many figures on volumetric water content and pore-water pressure in Sections 3.2 and 3.3. Can they be streamlined according to the content of the paper? For example, the similar change trend can be presented with a figure or a paragraph. In addition, abnormal data in the figures should be clarified.
Authors' response: Thanks a lot for your kind suggestion. A-E inside the flume model represents the crest, shoulder, middle, and foot of the slope respectively. The variation characteristics of the volume moisture content and pore water pressure at A, B, and C are relatively similar. Therefore, the figure of C is retained in the revised manuscript to indicate a general trend, while the figure of B is deleted. In addition, the three positions (C, D, and E) are close to the sliding surface. Thus, the data of these three positions are analyzed in Section 3.2, 3.3 and shown in Figure 6-Figure 18. Meanwhile, the interpretation of abnormal data in the figures has been supplemented. The Sections 3.2 and 3.3 have been streamlined and improved. The revised details can be found in Line 237-377.
In section 3.2, Figure 10(b)- Figure 12(b) show that the fluctuation of volumetric water content occurs in the second rainfall. Please offer a brief explanation for this phenomenon.
Authors' response: Thank you for your kind suggestion. At the beginning of the second rainfall in test 4, the maintenance of water pipe caused a short water stop. Therefore, the data fluctuated.
In Section 3.5, the authors explore the close relationship between the initial dry density, slope angle, rainfall intensity, and landslide initiation. Additionally, the initiation time of six landsides are compared. However, the detailed mechanism is still not clear. A deep discussion is needed.
Authors' response: Thanks a lot for your comment. In the discussion section, the mechanism of landslide initiation combined with the initial dry density, slope angle, rainfall intensity, and physical parameters of residual soil has been deeply analyzed. The revised details can be found in Line 420-440.
In section 4, the authors stated that the failure process of the granite residual soil landslide can be classified into five stages. Is it based on the six tests? Are five stages only summarized by the six tests?
Thank you to allow me to review this manuscript. Granite residual soil landslides are widely distributed in southeastern Guangxi, China. In this paper, the authors reproduced the failure mode and process of granite residual soil landslide by flume model tests. This work is interesting to read. However, some critical points should be addressed before the manuscript can be accepted.

Specific comments
(1) The entire manuscript should be polished by a native English speaker, as some sentences are not concise enough and there're some spelling or grammatical mistakes.
Authors' response: Thanks a lot for your kind suggestion. The paper has been earnestly streamlined, and the content has been carefully proofread to remove spelling and grammatical errors.
(2) In line 144-145, the particle size distribution of the granite residual soil has an "upward convex" part in Figure 2, which is impossible in the cumulative distribution curve. The authors should check the accuracy of the data and Figure 2. It is also recommended that the two important particle sizes in the article (2mm and 0.075mm) are marked in Figure 2.
Authors' response: Thank you for your comment. We have checked the data of particle gradation, there is no problem with the data. The soil content with a particle diameter between 1mm and 2 mm is relatively small, so the curve has a convex feature. The particle sizes including 2 mm and 0.075 mm have been marked in Figure 2. The revised details can be found in Line 130-131 and 143-144.
(3) In Section "3.1 Macroscopic phenomena of tests", the author intended to elaborate on the macroscopic phenomena of the slope during the 6 experimental tests. However, Figure  6 only shows the slopes after soil sliding in these 6 tests. Therefore, the authors may choose one test as an example, clarify the processes and characteristics of the tests based on the experimental photographs.
Authors' response: Thank you for your kind suggestion. Because the macroscopic phenomena in test 3 can fully reflect the whole processes of these six tests, we choose the test 3 to clarify the processes and characteristics of the tests. It can be found in Line 197-205 and 230-236.
(4) In sections "3.2 Moisture Content" and "3.3 Pore Water Pressure", the author explains the variation of the moisture content and pore water pressure during the experiments in detail, but the reasons for the variation have not been analyzed in depth. It is suggested that the author analyze the variations of water content and pore water pressure sensors, combined with the macroscopic phenomenon of the slope failure. The authors should deeply analyze the landslide failure processes, and try to reveal the failure mechanism based on your tests.