GENERAL COMMENTS

This paper documents changes to the unstable hillslopes adjacent to a retreating glacier using observations from satellite and UAV imagery and field visits. Three main types of hillslope response are documented – rockfall, debris sliding, and gullying – and the authors attempt to explain the occurrence of these with reference to observed changes in the climate and glacier. The paper presents data that is of interest for several reasons; 1) the research context - a relatively understudied type of glacier environment [monsoon temperate, within Southeast Tibet]; 2) several types of hillslope failure mechanisms are documented, adding to the growing knowledge of the complex response of hillslopes to glacier retreat; 3) the authors use these data to make observations on the interactions between hillslope and glacier processes, topical for research on alpine hazards, climate science, and paraglacial geomorphology. While the observations are of interest, the overall purpose and aim of the manuscript is a little unclear from the introduction, without the identification of key research questions tied to the objectives or without a set of hypotheses being developed and then tested. It rather feels like the data was collected for the sake of collecting it in the hope that it might yield some interesting observations (which it does, but the lack of a clear study setup/purpose detracts from the paper’s impact). The manuscript falls short of delivering any major discoveries that change the current understanding of landscape response to deglaciation, instead providing a more incremental increase in data documenting the range of responses (which in itself can be useful, but is currently not sufficiently capitalised upon). Other than further confirming the significant role of glacier down-wasting (which is already a very well-established process of hillslope destabilisation), the manuscript is unable to provide much more than speculation on other factors responsible for the hillslope response patterns observed (e.g. long-term strength reduction or frost weathering responsible for the rockfalls observed). On the interactions between the hillslopes and the glacier, these are also rather descriptive without detailed analysis. In my ‘specific comments’ below I offer some suggestions for how you might address some of these short comings and better utilise your (nice) data to give your manuscript more impact. I hope that the specific comments and technical corrections below will be useful in reshaping this manuscript and enhancing its clarity, focus, and overall contribution.

SPECIFIC COMMENTS

1. The introduction needs to do a better job of setting up the objectives of this work. For example, what key research gaps or questions (e.g. in paraglacial hillslope response) is the manuscript addressing? How will your 3 objectives stated on L82-87 help to address these? Why is the HLG study site important/useful for addressing these questions? (I note that on L113-117 there is clearly a hazard motivation for the selection of the HLG site, so perhaps this could be presented better in the introduction as one of the justifications for addressing the key research questions and for the selection of the HLG site).
2. The classification of the types of hillslope response could be better justified and used consistently throughout the manuscript: e.g., the description of the three types (A, B, C) are described differently in the abstract than in the conclusion (in which they are also labelled differently, as i, ii, iii). On lines 35-40 five main classes/modes of hillslope response are described from the literature, but it is not clear how the three types (Type A, B, C) described in the manuscript relate to these 5 modes. Also note that Mode (5) paraglacial debris cones and valley fills seems to describe a product of hillslope erosion, not a type/process/mechanism of hillslope response. Debris cones and valley fills presumably can be produced by a variety of mass movement processes. So there is some inconsistency in the 5 modes presented.
3. The term Paraglacial Slope Failures (PSFs) is used as a catch-all for the three main hillslope responses that are documented. However, given that the Type C response seems to be focused on headward gully erosion and said to involve fluvial processes (L411), it casts doubt on the suitability of the term ‘Paraglacial Slope Failure’ to represent this, as fluvial processes are not traditionally considered to be a slope failure process. Perhaps a better term is needed?
4. Related to the previous comment, I feel that the processes involved in the Type C response are somewhat unclear. Does this response type involve mostly debris flow processes (in which case the term PSF may be OK), or is it mostly fluvial erosion (rilling and gullying)? While I suspect there are not sufficient (temporal) data to confidently identify the processes causing expansion of these gully areas, perhaps there are clues from the deposits they produce (i.e. are the fans below these gullies more typical of fluvial or debris flow process?).
5. For each section of the Data and Methods (i.e. sections 3.1, 3.2, 3.3, 3.4) I suggest starting with a brief explanation of the purpose of the method, trying to link back to the objectives where relevant. This will help readers to understand why you are doing each part.
6. I would like to see some more explanation of how the three response types were identified, i.e. what key criteria were considered (i.e. elaborating on the comment on L228-230). As I understand it, they key criterion for assessing the presence of a hillslope response was the appearance of bare ground (especially sediment?). I have two potential issues/queries with this:
7. a) not all bare ground exposed by the glacier will be unstable, so how do you differentiate unstable ground from stable ground (e.g. using signs of disturbance, or a slope angle threshold?), and can you quantify the abundance of stable vs unstable ground?
8. b) You state that due to the climate conditions vegetation colonisation is extremely fast in this environment. This presumably means that much of the bare ground exposed in the early part of your study becomes colonised by vegetation by the end of your study, especially for Type B responses which do not necessarily prevent vegetation from establishing on the main body (i.e. vegetation rafting). Does this pose a challenge for the identification of bare ground through time, and if so how do you get around this or how much does it affect your results?
9. L148-149: Please elaborate upon how you calculated the ‘mean quality of 0.15 m in XY’. Did you calculate this by withholding a sub-set of your ground control points not used in the georegistration, in order to provide an independent check of georegistration error? It would be preferable to also provide the maximum error or at least a measure of dispersion (e.g. standard deviation), not just the mean.  Please explain what you mean by ‘successfully occupied positions’ or revise this wording to make it clearer what you are referring to.
10. The five profile lines A-E and their data (ice surface elevation, thinning rates, flow velocity) provide some interesting data on changes to the glacier, but it is hard to see how these data are actually used to help understand the hillslope response processes. It is unfortunate that these data are not more thoroughly used to explore the relationships in space and time between glacier changes and hillslope changes. Although on L452-454 you state ‘our analyses show a temporal and spatial component to PSF development’ there is no real attempt to combine the data of Figure 3 with the data of Figures 4-7 in any quantitative way. It might have been worth setting up a hypothesis, for example that the rate of Type B movement will correlate with the rate of ice thinning, or that the magnitude of ice thinning would correlate with the growth in size of Type B and Type C responses, and then quantitatively/systematically test these. Such relationships are only somewhat qualitatively/subjectively commented on in the manuscript. Likewise, why were four (and not some other number of) transverse profiles chosen and what was the rationale for their placement – was the hypothesis that thinning and hillslope response will differ depending on distance up-valley of the terminus, or were there differences in terrain type, geology, or some other environmental variable that were being captured in these profiles?
11. The glacier velocity data are interesting in themselves but do not seem to be well utilised or particularly relevant to the objectives. What was the hypothesis that was being explored with this, or why would changes in glacier velocity be expected to cause (or respond to?) hillslope processes? On L430-438 we get a sense that the velocity data is being used to infer that the high flow rates have been responsible for a high erosion rate and steepening of the valley flanks. But this is not supported with any data or further context – there are no data to show that the valley walls are steeper than other glacial valleys with lower flow velocities, and there is no comparison made between the rates of hillslope response in the HLG to other locations to explore whether the rates are unusually high and therefore are correlated with a high flow rate. I suggest that unless there is a good case for retaining the glacier velocity data, then it is removed from the manuscript because currently it adds little insight into the hillslope processes observed.
12. There could be more information provided on the rockfalls. At present it seems that only the largest is described in any detail, with the other failures described only in general terms (e.g L253 ‘We also observe other major rockfalls…suggesting that numerous smaller scale rock falls have occurred in this locality’ or L258 ‘small magnitude rockfalls occur more frequently’ Can you present the data for these events – e.g. a freq/mag histogram or table showing their source elevations, when they occurred, and their magnitude, and a map showing location? Presenting these data may help to tease out relationships between the failure patterns and the factors governing them.
13. The role of mass movements for producing supraglacial debris (e.g. L45-43) seems to be a theme introduced and returned to several times in the manuscript, but at present the manuscript makes little contribution to this topic. While rockfalls were observed to deposit sediment onto the glacier (e.g. L260, L448), this manuscript is hardly the first to identify the role of rockfall in producing supraglacial material so this is not a particularly helpful finding. Moreover the actual effect that these few documented failures have had to glacier ablation is not in anyway quantified in the manuscript, so as it stands the qualitative observation of supraglacial debris accumulation is not particularly insightful. Therefore, I would suggest that either this aspect of the manuscript is removed, to improve the focus of the manuscript, or this aspect is enhanced. Enhancements could be to:
14. a) provide more quantitative data on the total areal contributions to supraglacial cover of the rockfalls documented in the manuscript and make comparisons with other studies (i.e. substantiate the statement on L448-450 with data and context).
15. b) include a more detailed description of the contributions (or not) of the other two types of hillslope response (B and C). To what extent have these processes also delivered supraglacial material to the glacier during the observation period, and if they have been delivering sediment then to what extent has supraglacial sediment delivery by these types of hillslope process previously been documented in the literature, and are your findings consistent with that?
16. c) there is a nice opportunity to discuss sediment delivery to glacier systems more widely than just supraglacial sediment delivery. You pick up on the fact that some of the Type B failures are deforming the glacier (sensu McColl and Davies 2013), which is a nice observation – to what extent are these failures also delivering sediment sub-glacially, similar to what was identified by Cody et al., 2020 in the Fox Valley, or are the slopes at your site not engaging this recently-documented sediment pathway? Further, it appears that some of the Type C processes are providing sub-glacial water supply, and therefore presumably these are also delivering sediment to the sub-glacial environment? If so, exploring to what extent these paraglacial transport pathways (i.e. from recently exposed moraines) have been previously documented in the literature would be a good point of discussion.
17. Related to the previous point, on L45 you refer to the role of ‘high-frequency, low-magnitude PSFs’ in delivering a ‘considerable volume’ of debris onto glacier surfaces. But what about the low-frequency, high-magnitude events (e.g. large rock avalanches) that are well documented in the literature for their role in dramatically changing glacier ablation? Why do you focus on the small high-frequency events here?
18. L265, L270, & L287. Please describe the process(es) by which the Type B features become larger; e.g. is this through glacier downwasting exposing more of the slope, lateral expansion of the failure mass, or headward expansion from retrogressive failure or degradation of the scarp (e.g. from surface erosion processes)?
19. The observation of nested processes (e.g. gullies developing within Type B failures) is nice but it would have been great to see an analysis of the temporal evolution of these. For example, in Cody et al., 2020 they describe a temporal evolution in hillslope response, whereby moraines initially begin collapsing through sliding and internal deformation, and then later surficial debris flow processes (i.e. gully forming processes) takeover, and eventually both processes relax as the slope adjusts to its angle of repose. Are you able to see a similar or a different evolution in the slopes you observe? This would make another very nice comparison.
20. L272-275: Comparison is drawn between the Type B failure process and the conceptual model of moraine evolution by Eichel et al (2018). However, this comparison is hard to follow. Eichel et al describe a transition from an unstable state dominated by debris flows and gully erosion through to a period of solifluction modification, through to stabilisation. It appears to me that the typical Type B hillslope responses you describe in this manuscript seems to be more dominated by debris sliding than debris flow or gullying, and therefore is not a great comparison to stage A of the Eichel model (for the sites they studied) – perhaps your Type C is a better comparison? It would be good therefore, if you could further explain why you make this comparison, and it would be really interesting if you additionally compare the evolution of the moraines at your site to the other two stages of the Eichel model – do they also transition to solifluction and then stabilisation, i.e. the older lateral moraines nearer to the LIA terminus? Perhaps you can identify solifluction features in the imagery data or from your field visits, or perhaps the climate is not suitable for this? If you do find differences then you could instead suggest that at your site you observe a different evolution pathway to what is found for the European Alps? This would be a nice contrast and provide a rich vein of discussion (in the discussion section) if in fact there are differences that can be observed.
21. L300-306: Please elaborate further on what is meant by a ‘transition form’, and ‘landsliding behaviour’ and what is different between the two zones referred to.
22. The observation that south-facing slopes were generally more unstable than north-facing slopes is a potentially interesting observation, but one that is not robustly analysed. For example, the authors might consider a wider range of (intrinsic and extrinsic) factors explaining this difference, e.g: a) differences in the availability of material (i.e. asymmetrical deposition of glacial drift and moraine construction on either side of the valley), with more sediment on the south-facing slopes; b) asymmetry in morphology (i.e. differences in slope angle). The latter could be easily tested using DEM analysis; the former could possibly be explored through aerial image interpretation?
23. Section 5.1. Unfortunately, this section is heavily reliant on speculation, and analysis of only the 2018 rockfall. Analysing the location and timing of a single (and a not particularly spectacular) rockfall in the valley is not sufficient for making meaningful generalisations of the causes of rockfall in the valley. Perhaps this section could be strengthened if more attention was paid to the smaller rockfalls - e. examining patterns in the timing and location of several failures and not just a single failure.
24. L389-390: ‘instability typically have a slope angle of 25’.  Upon what basis is this statement made? Do you systematically measure the slope angles from the DEMs? Are you able to more robustly compare slope angles between the unstable debris-covered slopes and the stable debris-covered slopes to test whether the unstable sites tend to be oversteepened? Perhaps an examination of the slope angle of stabilised moraines closer to the LIA terminus will give some rough indication of the ‘long-term’  angle of repose of the till making up the moraines in the valley. This could provide a useful test of your hypothesis presented on L457 ‘we hypothesise that this (moraine collapse) will continue until critical angles of repose are reached which will be followed by vegetation colonization and advanced soil development’.
25. L395-402: The role of vegetation colonisation is (reasonably) discounted for stabilising the Type B failures that involve deeper-seated sliding, but what about the role of vegetation colonisation for stabilising other types of erosion process in the valley? Do you see a reduction in say Type C hillslope responses over time? Again, this might make for another comparison/contrast with the Eichel et al (2018) model.
26. L400-403: It is a shame that there was not more effort made to understand why all Type B sites appeared to increase in movement rate between 2017-2018. What further analysis could be done to explore this? Did Type C response (i.e. gullying) also increase? Can the data from Figure 3 be used to analyse this further? Did any slopes downstream of the glacier terminus show any increases in movement or erosion during this time (i.e. helping to rule out glacier thinning as a cause)?  Did the upper parts of the slope failures speed up to the same extent as the lower parts (perhaps more suggestive of rainfall as a driver) or did the lower part speed up the most (perhaps suggesting removal of toe support from ice thinning)?
27. In terms of key literature, please consider some of the following for examples of seminal or highly relevant work on moraine modification that could be referred to:

• Curry, A. M., & Ballantyne, C. K. (1999). Paraglacial modification of glacigenic sediment. Geografiska Annaler: Series A, Physical Geography, 81(3), 409-419.
• Curry, A. M. (2000). Observations on the distribution of paraglacial reworking of glacigenic drift in western Norway. Norsk Geografisk Tidsskrift, 54(4), 139-147.
• Curry, A. M. (1999). Paraglacial modification of slope form. Earth Surface Processes and Landforms: The Journal of the British Geomorphological Research Group, 24(13), 1213-1228.
• Ballantyne, C. K., & Benn, D. I. (1994). Paraglacial Slope Adjustment and Resedlmenfation following Recent Glacier Retreat, Fåbergstølsdalen, Norway. Arctic and Alpine Research, 26(3), 255-269.
• Curry, A. M., Cleasby, V., & Zukowskyj, P. (2006). Paraglacial response of steep, sediment‐mantled slopes to post‐‘Little Ice Age’glacier recession in the central Swiss Alps. Journal of Quaternary Science: Published for the Quaternary Research Association, 21(3), 211-225.

TECHNICAL CORRECTIONS

L19:  the term ‘slope slide and collapse’ is inconsistent with standard mass movement terminology. Consider revising (e.g. see Hungr et al., 2014 classification)

L37: remove ‘and’ after ‘(4)’ since this is not the end of the list.

L96: the statement ‘stretching to the Little Ice Age (LIA) end-moraine’ seems to contradict the later statement on L100 that the ‘HLG has retreated more than 2 km since the LIA’. Please reconcile.

L104: do you mean ‘proglacial’ instead of ‘preglacial’?

L113-117: perhaps this hazards rationale could be moved to or restated in the introduction.

L129-130: consider improving clarity of statement ‘NDVI can eliminate a part of the effect of hill-shade…’ (i.e. explain more clearly).

L132: consider different choice of words: ‘less suffered from’

L134: what is meant here by ‘partly’?

L137: add ‘and’ before ’19 August…’

L196-198: consider revising sentence ‘Field observations indicate…’ This is unclear and needs further elaboration.

L240: you describe the slope failure as coming from a ‘south-west facing slope’ but on L244 refer to a ‘steep north-facing slope’. Are these the same failure, and if so, is there a mistake with the latter?

L247-249: it is hardly a surprise that rockfalls are able to reach the glacier and become supraglacial debris. Perhaps this sentence adds little and can be removed?

L259: this sentence ‘each with a mean area of 750 m2’  reads that all 15 rockfalls had the same area. But I presume 750 m2 was the mean area, and that they each had different sizes?  Perhaps provide the size range.

L283: what type of ‘analysis’?

L329: what is ‘an increase in sediment-covered area’ referring to? Is this the supraglacial sediment cover?

L409-410: what is meant by ‘sediments were transported along the transport’? What is ‘with a fast erosion’ referring to?  ‘largest change in area of C1 travels about 150 m…’ is unclear. Confusing use the term ‘travels’.

L415: consider revising text ‘seasonal plus of enhanced or uprush erosion rates’. This is unclear.

L448: ‘a large number of debris fell into the glacier surface’  From which process? Rockfall, debris sliding, etc?

L486: this is the first mention of ‘debris avalanching’ so it should not appear in the conclusion for the first time.

Kind regards,

S McColl

In their manuscript, Zhong et al. map ten medium to large scale paraglacial slope failures (~24 to ~160 x 10³ m²) above the retreating and thinning Hailuogou Glacier (HLG) that descends from the Mount Gongga massif in eastern Tibet using repeated UAV and satellite imagery. Comparing the mapped failures to data on glacier dynamics, as well as temperature and precipitation trends from a nearby station, the authors contribute to the growing data on paraglacial landscape adjustment. While the body of literature on the topic of paraglacial geomorphology has been growing in the past years, Eastern Tibet, where the present study is located, has not received much attention in this respect. Despite the interesting data set the study offers, the manuscript lacks a clear formulation of a relevant research question, does not explain the applied methodology in sufficient detail, and offers conclusions that are not fully backed by the findings presented. Below, I will elaborate this in a number of general comments, before offering specific comments and technical corrections that hopefully will help the authors to improve their work.

Kind regards

Jan Blöthe

General comments:

Overall, the manuscript is well written, but sadly lacks rigorous identification of previous work and the work conducted here. Especially in chapter 3 (Methods and data), the authors need to put more effort into making it very clear, which information has been obtained from earlier studies and how the data produced in the framework of this manuscript was produced.

A very basic and important point that the authors fail to include in their work is a thorough error assessment of all measurements they conducted. This is neither addressed in the methods section, where it remains rather unclear how exactly mapping has been conducted, nor are the errors associated with mapping (based on visual interpretation?) in remotely sensed imagery discussed later in the text. For

Chapter 3.2: Here the authors mainly present details of earlier studies that quantified glacier mass balances changes of the HLG. I would recommend to include these background information into the description of the study area (Chapter 2) and shift the focus of Chapter 3.2 to the method applied here. From the technical description in L158-164, I take that the authors used three digital elevation models (DEMs), namely “the TopoDEM (1966), the Shuttle Radar Topography Mission (SRTM) 30m DEM (2000) and the ASTER-DEM difference between 2000 and 2016”. While I am familiar with the latter two (the ASTER DEM data is from Brun et al. 2017, include reference here), I am not aware of the TopoDEM (1966). If this refers to the DEMs calculated in Cao et al. (2019), this needs to be indicated here. Moreover, from the technical details outlined here, it remains unclear to me whether the authors only analyzed five profile lines, or calculated full DEMs of difference and used five profile lines to visualize the data. Please elaborate this in more detail and outline, in the case data was only analyzed along five profile lines, how these are encompassing the full variability of surface changes on the glacier tongue.

Furthermore, in L165-174 (still Chapter 3.2), the results of earlier studies that quantified ice flow dynamics are presented. In the final sentence the authors describe a comparison of “long-term ice flow velocity changes […], based on three-periods results of 1982-1983 (in situ observed), 2007-2011 and 2014-2018 (SAR satellite derived).” Where does this data come from? Is this an analysis done by the authors, or does it refer to the studies presented before? As the dates mentioned here do not match the time spans given for the studies cited above, I would ask the authors to either clearly indicate the provenance of these data.

Chapter 3.3: This is a very brief description of how slope movement was quantified, given that large parts of the results and discussion build upon this data. While manual tracking of tie points in repeated imagery can be considered a fairly robust technique, I would recommend that the authors at least try to quantify the error associated with this tracking of tie points. This can be easily achieved by tracking stable surfaces in the vicinity of the slope failures. Furthermore, may I suggest to include the individual vectors for manually tracked tie points in Fig. S2? Last but not least, let me point out that there are multiple software solutions that allow for automated tracking in consecutive imagery, which would result in full 2D velocity fields that might enable a much deeper insight into the mechanisms of the failures (and reveal local variability).

Section 5.1.1: Here the authors discuss the possible preparatory and triggering factors for the rock fall they observe during their study period. The authors might want to further elaborate how the exceedance of a precipitation threshold of 60 mm for a single day in June 2018 is connected to the triggering of a rock fall in October 2018. This is mainly referring to L362-65 and Tab. 3, where the authors argue for a precipitation intensity anomaly, which I find hard to follow given the data. Yes, 2018 has seen one day with more than 60 mm of daily rainfall, i.e. 61 mm (L364). Without giving more details on the exact precipitation values for 2016 that also saw three days with more than 40 mm per day, I do not think this can be seen as an indication for a precipitation intensity anomaly. In my view, it would be worth to look at the antecedent rainfall in the five to ten days before the failure and compare antecedent rainfall statistics between years, especially in a setting with very few days without rainfall. Furthermore, in section 5.1.1 the authors argue for a potential triggering by frost action. It is my feeling that also this remains speculative, as the cold interval the authors refer to here (01-09 October 2018; L369, Fig. S4) happened at least 5 days before the failure that the authors date to 15 October 2018. However, the temperature data for 2018 is unavailable for the days following 09 October, making this link questionable.

Specific comments:

• L35-40: Here the authors gather five modes of response to slope failure, though I have the feeling that mode 5 “paraglacial debris cones and valley fills” is rather the results, i.e. deposit of the processes listed in 1-4.
• L67-68: Not really relevant at this point, as the tourism activity at the site is detailed in L109-117.
• L101-02: In L152-53, this information is from Zhang et al. 2010, please add reference here
• L124: How was the glacial area mapped exactly? As the HLG is debris-covered, a precise delineation between debris-covered ice and the debris-covered surroundings is not trivial. Please elaborate in detail, how mapping of glacier extent was conducted and what the associated uncertainty of this mapping was.
• L124-26: Also for the paraglacial slope failures (PSFs), it is not clear how exactly these were mapped. In L121-24 it is described that using the NDVI, vegetation covered areas were excluded. But how exactly was the mapping of the PSFs achieved in remote sensing imagery. What were the criteria for mapping? Was this mapping field-evidence based and if so, when was field-work conducted?
• L130-34: Again, it remains unclear at this point how PSF boundaries were extracted, what validation means in this respect and based on which criteria manual correction was done.
• L138: I would suggest to state this in more detail. At this point, it is unclear, whether the “mean quality of 0.01 m” refers to the position accuracy of the RTK UAV, or to the SFM output. Furthermore, “+1 ppm (RMS) in XY” is neither clear in this regard. In order to allow the reader to follow and to judge the quality of the data used in this study, I suggest to explain in detail, how the UAV images were processed and what the residual mismatch of their geolocation is.
• L142-43: I take it that the authors co-registered and orthorectified the UAV-derived orthomosaics with the PALSAR DEM, or is the sentence correct that individual UAV images were used for this? May I ask the authors to elaborate this a bit more, as this is cionfucing? IN line XX you write that these are already orthorectified?
• L156: The authors compiled a data set here, but I fail to see where this data set is included in the manuscript? Is there a figure or table that shows this compilation?
• L174: In the very brief section following this heading, the “outline change rate” is not mentioned nor explained how this is quantified. Instead, the authors quantify the rate of headscarp erosion. Consider rephrasing the heading here.
• L178-180: May I suggest to elaborate more clearly how the outlines of failures were used to calculate a mean annual retreat rate for headscarps?
• L220-23: The time spans given here in the text are not the same as in Fig. 4. What is the rate between 2000 and 2019?
• L224: Which area are you referring to here?
• L225-26: Where is the data for the lower frequency of PSFs?
• L227: Where does the knowledge of slope material come from? Did you map out slope material distribution during field work?
• L239-44: This description of the rock fall (PSF type A) needs to be refined. In L240 it is stated that the rock fall occurred on a south-west facing slope, while in L244 it is stated that the mass detached from a steep north-facing slope? Is it that the general topography is south-facing and the nice of the detachment faces north? The picture in Fig. 5b, however, does look like the source is also facing the glacier – please clarify.
• L241-42: This is not precise enough. How can a deposit of a rock fall be “450m in height fro the glacier surface” and at the same time, “cover a height of 380 m”?
• L258-59: Please indicate what magnitude is considered small here, as to me “each with a mean area of 750 m²” is not clear.
• L262-63: Please try to be consistent in labelling the processes: “Sediment-mantled slopes slide and collapse” vs. “Sediment-mantled slope slide and collapse”. In my view, both seem a bit clumsy – you might want to rephrase.
• L263-66: The numbers given here are surprisingly round and do not match the sums of the individual numbers mentioned in Tab. 2. Also, in Tab. 2, there are no errors associated with the numbers given for the area. Please include a statement on the precision of these estimates in the text. This also applies to L310.
• L271-75: This comes as a surprise here and rather belongs to the discussion.
• L276-78: How was the error of 0.04 cm d^-1 quantified?
• L283: How do the authors know that the detectable slope movement began around 2000? Has this been published, or did the authors run additional analysis beyond the 2016-2019 UAV surveys that have been described in the text. Same applies for L296.
• L286: “the landslide has fallen” sounds as if it was a vertical movement that was quantified? Until now, it is my understanding that the authors quantified 2D horizontal displacement.
• L400-02: This comes as a surprise as a) in L361-62 the authors argue that 2018 has seen relatively low temperature. Furthermore, Fig. 9 suggests that 2017 has a data gap in temperature readings.
• L430-38: I am not sure how this is connected to the data and topic presented in this study? Consider removing paragraph or elaborate the connection to paraglacial slope adjustment.
• L444-46: Is this supposed to be a general statement? Also, check grammar.
• L448-50: It is hard to see how the deposition of debris onto the glacier is directly affecting climate. As the authors try to outline in Figure 8, debris cover generated by slope failure might have an effect on glacier downwasting, which in turn can have a tiny effect on the climate.
• L464-70: While McColl and Davies (2013) showed that also failures of similar magnitude as B2 in the present study can deform glacier-ice at the rate of mm/yr (assuming a min. average thickness of ~1 m), the evidence presented here is limited and the discussion of this aspect remains too surficial. It might be a way forward, to present the displacement data in more detail and quantify the supposed narrowing and squeezing effect that is mentioned here to back this aspect with data.
• L474-75:What data is this statement based on? Is there a study that found this increase in debris-flows and flash-floods that could be cited here?
• L482: In L195-96 the authors state that between 2016-2019 the glacier terminus retreated by >150 m with a rate of ~52 m yr^-1. Which is true?
• L485-86: In your data, type A landslides are limited to one rock fall. Did you find evidence for debris avalanches as well?
• Figure 1: Might I suggest to add the glacier outline for the years 1982/83, as in the text the authors have quantified (or cited) the displacement values for this period (Fig. 3).
• Figure 3: Is there a reason for the black line being thinner in D-D` of the first column? Also, in the caption, replace annual thinning rate with average annual thinning rate, as these have been quantified over multiple years, right? What remains unclear is the provenance of the data shown in the right column. Has this data been calculated from remote sensing data by the authors? If not, add the references to the data to the caption.
• Figure 4: Change “(white line)” to “(blue line)” in the caption, as this is showing the glacier outline, judging from the legend.
• Figure 6: Might I suggest to label the vertical axis of the last column with “displacement velocity”? Slide velocity implies a vertical component, but these are horizontal displacement values, right? Furthermore, in the caption, what does the reference to Qiao Liu et al. imply? Has this data been published before? I cannot find this reference in the reference list.
• Figure 8: May I suggest to give this figure a more detailed caption that explains the arrows and the reciprocal effects? Also, why does Type C have a larger arrow than Type A and B, what exactly does “remarkable glacial debuttressing” imply? Also check grammar of text box PSF Type A.
• Figure 9: Here it should be indicated over which time window the moving average for temperature and precipitation has been calculated. Furthermore, the reason for and length of the temperature data gap in 2017 should be mentioned in the caption. Also, are Tem_smooth and Pre_smooth appropriate abbreviations for a running mean of these variables?

Technical corrections:

• L130: delete “can”
• L132: “generally suffered less from” (?) instead of “are generally less suffered from”?
• L136-140: very long and in my view incomplete sentence; check grammar
• L166-67: check grammar
• L196-98: please rephrase
• L228-29: broadly coincide with?
• L239-41: “rock fall event […] occurred around October 15, 2018”? Check grammar
• L246-249: check grammar
• L250: “can thus can be some clearly”?
• L256: delete “are”
• L259-61: please rephrase, not clear what exactly this refers to and how relevant a mean distance to the glacier is in this context.
• L301-04: check grammar
• L309: seasonal snowmelt
• L 310: Numbers in Tab.2
• L335: glaciofluvial sediment instead of glaciofluvially transported glacial sediment
• L362: You should maintain the figure order! Figure 8 has not been referenced in the text and is only done so in L450.
• L361-62: There is no temperature given for 2017 and both 2014 and 2015 seem to be below 5°C, so I don’t think you can make this statement
• L373: freezing of water begins?
• L389: delete hosting
• L409-10: check grammar
• L414: check grammar
• L415: uprush? Can this be used in this context?
• L418: HLG
• L441: obvious compared to?
• L448: replace into with onto