| 04 Jan 2026
Unreported mass movements and future hazard in the Warwan basin, Jammu and Kashmir, Western Himalaya
Abstract. The Warwan sub-basin in Jammu and Kashmir is a remote glaciated region containing several glacial lakes and has recently experienced population growth and infrastructure development. Due to inaccessibility and geomorphic masking, multiple mass movement events including avalanches and Glacial Lake Outburst Floods (GLOFs) have remained largely unreported. This study analyzes three major avalanche events from the past two decades. The September 2005 and September 2020 avalanches originated from glaciers GL-B and GL-A within the same glacier complex, while the March 2020 rock–ice avalanche initiated from the headwall of glacier GL-F in an adjacent valley and terminated before reaching its ablation zone. Runout mapping shows that the September 2020 avalanche descended from the headwall of GL-A and impacted its proglacial lake, triggering a GLOF. In contrast, the September 2005 event terminated before reaching the glacial lake that began forming in 1999 at the terminus of GL-B. Geomorphic analysis indicates persistent sediment influx from meltwater streams of GL-D and GL-E into the lake associated with GL-A, progressively infilling the basin. Continued glacier retreat caused meltwater to accumulate behind the sediment infill, dividing the basin into two disconnected lakes. Impact from the September 2020 avalanche led to complete drainage of stored water and sediment, generating a downstream debris flow. Pre- and post-GLOF imagery reveals breaching and widening of the outflow channel and deposition of a debris fan downstream. The repeated history of mass movements and continued growth of glacial lakes raise serious hazard concerns in the Warwan sub-basin. GLOF modeling identifies Lake-B as potentially hazardous lake at the present condition posing significant downstream risk. Settlements such as Youdu and Qaderna, along with bridges, roads, and residential structures, lie within potential GLOF inundation zones. High sediment availability from past mobilization and deposition along the valley increases the potential of debris flow cascades, posing elevated risks to downstream infrastructure and hydropower, underscoring the need for preparedness and mitigation planning. GLOF modeling suggest that early warning system closer to the source will be able to provide a good lead time in case of potential GLOFs in the valley.
General comments:
This study presents evidence for previously unreported hazards/hazard cascades in a basin containing five glaciers (plus one more nearby) in the Western Himalaya. It is shown how several avalanches have occurred onto glaciers, in one case entering a glacial lake and triggering a small GLOF. These events appear to have been unreported at the time they occurred, indicating they had minimal impact on immediate downstream communities. However, the point is made that similar hazards in the future from the basin have the potential to be more problematic, and avalanche and GLOF modelling effectively demonstrates this. Thus, this is a useful contribution to the literature on a very important topic. I do however think that improvements can be made to the paper as it stands, particularly to streamline the text and figures and improve consistency of terminology and how this appears across the text and figures, in addition to a number of other minor edits to improve the clarity of the writing throughout.
Specific comments:
Technical suggestions:
Abstract
Page 1, line 5: I don’t think “glacial lake outburst floods” needs to be capitalised in this way.
Page 1, line 21: “a” is missing before “potentially hazardous”. Also suggest “in its present condition” instead of “at the present condition”
Introduction
Page 2, lines 2-5: It is not clear if this is referring to global glacier loss or regional loss in High Mountain Asia, for example. Suggest clarifying this as most of the references appear to relate to HMA (or HKH as you use).
Page 2, lines 10-12: Suggest “pose a challenge to” instead of “challenge”
Page 2, lines 17-19: I’m missing the time period covered by these reported increases in lake numbers – is this still referring to the last three decades? Suggest adding this for clarification.
Page 2, line 20: suggest adding “formed in front of retreating glaciers” after “glacial lakes to clarify that you are not dealing with ice-dammed or supraglacial lakes.
Page 2, lines 20-21: I don’t think “glacial lake outburst floods” needs to be capitalised in this way.
Page 2, line 25: suggest “that threatens” instead of “and threatens”
Page 2, line 30: remove “and” before “affecting” as there is another “and…” later in the list.
Page 2, line 31: “destroying” would fit better with the verb form in the rest of this sentence.
Page 3, line 2: suggest “have been” instead of “were”
Page 3, lines 4-6 “which was amplified by the huge debris eroded along the channel where the 2015 Gorkha earthquake deposited the majority of the debris” – this is slightly untidy phrasing and could be improved.
Page 3, lines 7-8: Why not simply: “The village of Til was impacted by bank erosion and collapse” ?
Page 3, lines 11: Suggest “a GLOF” and “a debris flow”
Page 3, line 20: “mass movements”
Page 3, line 21: these two citations seem to relate only to GLOFs in the Himalaya, so don’t really support the “GLOFs and mass movements” and “globally and regionally” points. I suggest adding more refs here to cover these.
Page 3, line 23: “after” should be “since”
Page 3, lines 24: are “new” and “unreported” both needed here?
Page 3, lines 24-26: what are “GLOF sources”? Does this mean lakes that produced GLOFs? Rewording this would improve clarity. “~95% moraine-dammed glacial lakes” needs to be integrated into the sentence better. “were located in the Himalaya” is needed.
Page 3, lines 28-30: “Identifying these unreported past events is therefore crucial for reconstructing geomorphic process regimes and understanding the hazard frequency in mountain catchments”. I would swap the order of these in the sentence – the contribution to understanding hazard frequency seem the important point that follows immediately from the preceding sentence. What are “geomorphic process regimes”? I feel that this could be rephrased in simpler language. Perhaps just “geomorphic processes”?
Page 4, lines 3-13: This paragraph seems out of place. Either it should be incorporated in the study area section, or in the earlier paragraph in the introduction that describes some examples of GLOFs (although I would argue this is probably too many examples for there).
Page 4, lines 14-31: These two paragraphs should be combined and shortened into a snappier “purpose of this study” paragraph. Twice in three sentences “Here, we…” is used, as an example. Save the details for the methods and elsewhere.
Study area and importance of the region
Page 5, lines 2-19: watershed and catchment are both used in this paragraph, suggest sticking with one.
Page 5, lines 4-5: how important is 0.8 km2 and .61 km2 in these values? Especially as the glacier data is reportedly >10 years (or more? 2000) old. Suggest rounding to whole integers.
Page 5, lines 6-9: This data is presumably RGI outlines based on the citation, so it is important to state that here, and which version, e.g. RGI 7.0 (which you can cite directly, e.g. https://nsidc.org/data/nsidc-0770/versions/7). You should also then qualify the date stamp on these dimensions, which according to the RGI 7.0 information is “approximately the year 2000”.
Page 5, lines 9-10: “are associated with proglacial lakes” – can you be more specific, are these glaciers in direct contact with the lakes? And can you say when this was the case?
Page 5, lines 10-11: “…and have experienced mass movement events in September 2020 and 2005” – isn’t this the results from this paper? If so, I suggest removing from here.
Page 5, line 12 “Fariabad Nalla” – the spelling is different on Figure 1.
Page 5, line 13: use “the Marusudar River” on both occurrences in this line. Where is this river located on Figure 1? Where is Yordu village?
Page 5, line 14: Chenab River and Bandarkoot – are these beyond the Figure 1 study area? These should be labelled really.
Page 5, lines 16-19: this sentence “According to…” is out of place and would be better placed after you first introduced the glacier dimensions. You also don’t need the second citation to the same study.
Page 5, line 20: These placenames should all be on Figure 1 in the same format (e.g. “Metwan” or “Metwan village”)
Page 5, line 26: what and where is the “Kishtwar Window”?
Page 6, lines 3-7: Panel A - The shortened letters in the figure inset map need explaining: J and K, LDK, HP. Panels B and C - I’d suggest explaining what the different colour polygons are in the caption: red, grey and turquoise (presumably avalanche source, runout and lakes) – or add a legend.
Data and methods
Page 7, line 4: Suggest “images” instead of “imageries” and “imagery” - the next sentence calls them images.
Page 7, lines 5-9: These sentences can be combined to make the writing more succinct.
Page 7, line 8: how are “past GLOFs” determined from satellite images?
Page 7, line 8: spell-out “FCC”
Page 7, line 10: “images” not “imageries”
Page 7, line 11: see comments on study area section about RGI – this should be clearly stated there too.
Page 7, line 12: again, how are past GLOFs identified from satellite images? More details are needed. How is ice calving detected, and is this dry calving or in the lakes? Did you examine temporal images to identify new calving events? More details also needed on this.
Page 7, lines 14-16: Mapping uncertainty – you use Landsat and Planet images, so which pixel size is used for the uncertainty analysis? State this here. It sounds like the mapping was mostly done from the Landsat data.
Page 7, line 28: “pre- and post-event PlanetScope imagery” – unless I’m mistaken, aren’t some of your avalanches from before Planet images were available? Best to clarify this here.
Page 8, line 16: “To estimate the future volume…”, “we first matched its potential maximum extent…” – future volume and potential maximum extent of what?
Page 8, lines 27-30: check “D. D. More” citation – this appears to include initials.
Page 9, lines 2-6: “SC-1” etc. on the figure needs to be explained in the caption.
Page 10, lines 2-3: I think the Shugar et al. citation should probably come immediately after “the Chamoli event”.
Page 10, lines 3-5: Sentence beginning “Similarly,…” is missing some words.
Page 10, lines 23: Sections 1-3 should be identified on a map somewhere.
Results
Page 11, lines 4-5: Figure 4 should be cited before figure 5, or perhaps the order of these figures should be swapped.
Page 11, lines 8-9: “shifts in the thermal regime” – what is meant by this and how does it link to the “water-ice interactions”? More details needed here if you are to keep this interpretation.
Page 11, lines 12-14: sentence beginning “While Lake A…” doesn’t work currently. I suggest removing “while”, “has” and “only”. Should this also be “Lake-A” for consistency?
Page 12, lines 3-7: It would make sense to use “Lake-A” here so the reader is clear how this name links to the figures.
Page 12, lines 9-11: add labels to the fore-basin and main basin to Figure 4.
Page 12, line 9: alluvial fan should be used on Figures 3 and 4 too so it is clear what feature you are describing here.
Page 13, line 4: “proglacial” isn’t needed here.
Page 13, line 7: can remove “(or floating ice)”
Page 13, line 9: Why is the alluvial fan included in the lake basin area? Doesn’t this incorrectly inflate the lake area as there is no water where the fan is? This would then have knock-on effects on any further calculations from lake area, such as volume. I would just use the two basins where water is clearly visible for your lake area calculations, or provide a clearer explanation for including it.
Page 14, line 16: suggest “infilled sediment”. Is this the alluvial fan? If so, it would be helpful to use the same terms.
Page 14, lines 17-18: “Following the event, satellite imagery revealed breaching of the Lake-A moraine, extensive GLOF outwash, and subsequent deposition in the downstream channel.” – here is one of the places where it would be good to understand how this GLOF then went on to impact Lake-B, immediately downstream.
Page 14, line 18 to page 15, line 2: You seem to be suggesting that the lake formed entirely from melting of ice in the drained basin, what about meltwater inputs from the various glaciers that feed the basin? These surely also had an input. Also, debris can’t strictly melt so suggest rephrasing.
Page 15, line 3: Remove “Again” because this is a different glacier.
Page 15, lines 8-10: “water seepage” – what do you mean by this? Meltwater emerging from this side of the glacier for the first time? This is also not immediately obvious from the figure, so you should label exactly where you infer this is happening and explain what the evidence is for water seepage.
Page 15, lines 10-11: “This seepage contributed to the development of extensive crevassing” – why is this the case? Further explanation is needed as the link between water emerging from the glacier and increased crevassing is not immediately clear to me.
Page 15, line 15: “However” is not needed here.
Page 15, line 16: “after” should be “since”. The comma after “Owing to this” should be moved to line 17 after “size”.
Page 15, lines 18-21: Sentence beginning “It is also noted…” needs to be edited and rephrased and is doesn’t work currently.
Page 16, lines 2-6: It would make sense to use “Lake-B” here so the reader is clear how this name links to the figures.
Page 21, line 12: “the” is not needed before “Lake-B”.
Page 22, line 15: Delete “at”. Check spelling of “MaruSudar”
Page 22, line: “reach” instead of “are reaching”
Discussion
Page 25, line 4: See also recent paper for this point, which could be cited here: Pepin et al. (2025) - https://www.nature.com/articles/s43017-025-00740-4
Page 25, lines 9-10: “Zheng et al. (2021) reported that at least 21 GLOF events occurred per year in the region from 1900 to 2016, with the majority being unreported (Zheng et al., 2021a).” – how can GLOFs be both reported and unreported? Suggest rephrasing this so it is clear what is meant.
Page 25, lines 11-13: Suggest defining “unreported GLOFs” here – these are GLOFs that were not reported at the time they occurred? Or have not previously been reported, but have been identified retrospectively? Note “GLOFs” not “GLOF”.
Page 25, lines 14-16: This sentence would be better placed in the paragraph before, after the sentence ending with the citation “Harrison et al. 2018”.
Page 28, line 2: “proglacial” would be a better term here than “periglacial”.
Page 29, lines 10-12: Unless I missed it, this is the first time I see reference to the 2020 GLOF not impacting Lake-B. I think this should be explained clearly earlier in the results.
Page 30, line 9: “The Lake-B present…” should be “Lake-B presents…”
Page 30, lines 13-14: “High-resolution imagery shows that several settlements have emerged near the river in the past two decades” – the imagery shows that the settlements are there, but not that they have emerged as it is a single timestep. Suggest rephrasing
Page 30, line 15: “could” not “can”
Page 31, lines19-22: sentence starting “Recent observations…” – this is repetitive from the paragraph above, remove and merge the final sentence in this paragraph with the previous paragraph.
Page 31, lines 27-28: “We reconstructed…” – the way this is phrased, it could be mistaken for a description of different avalanches, but you are still talking about the same ones from the previous paragraphs. Editing the phrasing here would improve this link and the fluency of the writing.
Page 32, line 16: “Mass-wasting”… until now this term hasn’t been used I don’t believe, but mass movements has. I suggest you use consistent terms unless you intend there to be a different meaning here.
Page 32, line 28: “GLOFs”
Page 34, line 4: “MaruSudar River” – check spelling as it is different elsewhere.
Page 34, line 5: Make sure these locations are labelled on a map somewhere.
Page 34, paragraph 1, final sentence: Could also add 2022 Shisper Glacier GLOF in the Karakoram, which caused a lot of damage to infrastructure: Muhammad et al. (2021: https://www.tandfonline.com/doi/full/10.1080/19475705.2021.1975833)
Page 34, paragraph 2, final sentence: “In this region” – suggest you are more explicit that you mean the basin you have studied.
Page 34, paragraph 3, first sentence: do you mean the “modelled high-magnitude scenario flow channel” – suggest adding this if so.
Page 35, paragraph 1, first sentence: remind the reader that SC-1 is the worst-case scenario.
Page 35, paragraph 1, sentences 2 and 3: these are currently grammatically incorrect sentences and should be merged or edited.
Page 35, paragraph 1, sentence 4: what form could an early warning system take? A stream gauge of some sort to detect increased discharge? Some detail here would be helpful.
Page 35, paragraph 1: “Also, for a conservative approach effective adaptation requires integrated approaches that combine glacial lake hazard assessments with community-based vulnerability evaluations and social protection policies.” – I can’t follow this sentence at present, it should be rephrased.
Page 35, paragraph 1, final sentence: the last bit of this sentence is unnecessary as this has just been stated in the previous sentence.
Conclusions (note - no line numbers here)
Page 35, paragraph 2, first sentence: “past two and a half decades” – why not “25 years”?
Page 35, paragraph 2: “mass-wasting” – see previous comments on whether “mass movements” would be better, given the article title.
Figures
Figure 1: Adding an arrow to the GLOF path in panel (B) would be helpful. Make sure all placenames mentioned in the text are labelled on the maps wherever possible, and spellings match between text and figure. Label Lakes A and B.
Figure 4: Adding arrows to the drainage paths would be helpful. Label fore-basin and main basin
Figure 6: The avalanche runout label is not very clear – it took me a while to realise this related to the red dashed outline because the label overlaps with the glacier outline. Suggest making this clearer.
Figure 7: Label avalanche runout.
Figure 9: panel labels are lowercase letters here, elsewhere they are capitals.
Figure 10: the bridge symbol should be in the legend. Yordu is in the caption but not labelled on the figure.
Figure 11: I’m not convinced this schematic figure is required – the events depicted here are already described well in the text and Figure 3.
Figure 12: Suggest moving this to the results. Panel labels are lowercase letters here, elsewhere they are capitals
Figure 13: Similar point to Figure 11 – this isn’t really needed in my view, and there are already quite a lot of figures.
Figure 14: This seems like it would fit better in the results too.
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Harold Lovell
University of Portsmouth
29th January 2026