An inventory of historical glacial lake outburst floods in the Himalayas based on remote sensing observations and geomorphological analysis

2018·7.8 MB·English

by  Yong Nie

Geomorphology308(2018)91–106
ContentslistsavailableatScienceDirect
Geomorphology
journal homepage: www.elsevier.com/locate/geomorph
An inventory of historical glacial lake outburst floods in the Himalayas
based on remote sensing observations and geomorphological analysis
YongNiea,⁎,QiaoLiua,JidaWangb,YiliZhangc,YongweiShengd,ShiyinLiue
aInstituteofMountainHazardsandEnvironment,ChineseAcademyofSciences,Chengdu,Sichuan610041,China
bDepartmentofGeography,KansasStateUniversity,Manhattan,KS66506,USA
cKeyLaboratoryofLandSurfacePatternandSimulation,InstituteofGeographicSciencesandNaturalResourcesResearch,ChineseAcademyofSciences,Beijing100101,China
dDepartmentofGeography,UniversityofCalifornia,LosAngeles(UCLA),LosAngeles,CA90095,USA
eInstituteofInternationalRiversandEco-security,YunnanUniversity,Kunming,Yunnan650500,China
a r t i c l e i n f o a b s t r a c t
Articlehistory: Glaciallakeoutburstfloods(GLOFs)areauniquetypeofnaturalhazardinthecryospherethatmayresultincat-
Received30November2017 astrophicfatalitiesanddamages.TheHimalayasareknownasoneoftheworld'smostGLOF-vulnerablezones.
Receivedinrevisedform2February2018 EffectivehazardassessmentsandriskmanagementrequireathoroughinventoryofhistoricalGLOFeventsacross
Accepted2February2018
theHimalayas,whichishithertoabsent.ExistingstudiesimplythatnumeroushistoricalGLOFeventsareconten-
Availableonline6February2018 tiousbecauseofdiscrepantgeographiccoordinates,names,oroutbursttime,requiringfurtherverifications.This
studyreviewsandverifiesover60historicalGLOFeventsacrosstheHimalayasusingacomprehensivemethod
Keywords:
Glaciallakeoutburstflood thatcombinesliteraturedocumentations,archivalremotesensingobservations,geomorphologicalanalysis,
Remotesensing andfieldinvestigations.Asaresult,threeunreportedGLOFeventswerediscoveredfromremotesensingimages
Climatechange andgeomorphologicalanalysis.Elevensuspiciouseventswereidentifiedandsuggestedtobeexcluded.The
TheHimalayas propertiesoffiveoutburstlakes,i.e.,Degaco,ChongbaxiaTsho,Geiqu,LemthangTsho,andalakeonTshojoGla-
cier,werecorrectedorupdated.Atotalof51GLOFeventswereverifiedtobeconvincing,andtheseoutburstlakes
wereclassifiedintothreecategoriesaccordingtotheirstatusesinthepastdecades,namelydisappeared(12),sta-
ble(30),andexpanding(9).StatisticsoftheverifiedGLOFeventsshowthatGLOFtendedtooccurbetweenApril
andOctoberintheHimalayas.Wesuggestthatmoreattentionshouldbepaidtorapidlyexpandingglaciallakes
withhighpossibilityofrepetitiveoutbursts.Thisstudyalsodemonstratestheeffectivenessofintegratingremote
sensingandgeomorphicinterpretationsinidentifyingandverifyingGLOFeventsinremotealpineenvironments.
ThisinventoryofGLOFswitharangeofcriticalattributes(e.g.,locations,time,andmechanisms)willbenefitthe
continuousmonitoringandpredictionofpotentiallydangerousglaciallakesandcontributetooutburst-induced
riskassessmentsandhazardmitigations.
©2017ElsevierB.V.Allrightsreserved.
1.Introduction Kattelmann,2003;Bajracharyaetal.,2008;ICIMOD,2011;Liuetal.,
2014;Gurungetal.,2017),andChorabariLakein2013,locatedinthe
Aglaciallakeoutburstflood(GLOF)isauniquenaturalhazardthat Alaknanda River basin in India (Durga Rao et al., 2014; Das et al.,
occursinthecryospherewhenamorainedamfailedwithasubsequent 2015).TheHimalayas(Fig.1),occupyingatotalareaof~0.65million
suddenreleaseofwaterfromtheglaciallake(Westobyetal.,2014a, km2andcontaining22,800km2glaciers(Bolchetal.,2012;Nieetal.,
2014b).HistoricalGLOFsintheHimalayashavecausedcatastrophic 2017),areknownasoneoftheworld'smajorGLOF-vulnerableregions
fatalities and destructions in the downstream zones (ICIMOD (The (Quinceyetal.,2005;CarrivickandTweed,2016;Nieetal.,2017).Gla-
InternationalCentreforIntegratedMountainDevelopment),2011), cierrecessioninresponsetoclimatewarminghasresultedintheforma-
forexample,theoutburstsofCirenmacoin1981,locatedintheSun tionandexpansionofHimalayanglaciallakes(Kangetal.,2010;Nie
Koshi River basin in China (Xu and Feng, 1989; Chen et al., 2007; etal.,2013,2017;Songetal.,2017)andincreasedtheriskofGLOFs,
Wang et al., 2015a), Dig Tsho in 1985 (Richardson and Reynolds, which deserve increasing attention owing to their potential cata-
2000;Bajracharyaetal.,2007)andTamPokhariin1998,locatedin strophicdamages.
Dudh Koshi in Nepal (Xu and Feng, 1989; Mool et al., 2001; AdatabaseofGLOFeventscompiledfromexistingliteratureises-
sentialtorevealtheprocessandmechanismofGLOFsforhazardassess-
⁎ Correspondingauthor. ment,mitigation,andconsequentlyriskmanagement.GLOFevents
E-mailaddress:[email protected](Y.Nie). havebeenreportedintheBhutanHimalayas(GeologicalSurveyof
https://doi.org/10.1016/j.geomorph.2018.02.002
0169-555X/©2017ElsevierB.V.Allrightsreserved.
92 Y.Nieetal./Geomorphology308(2018)91–106
Fig.1.DistributionofhistoricalGLOFsintheHimalayas;thebackgroundimageisfromESRI'sworldbasemap.
Bhutan,1999;Komorietal.,2012),inTibet,China(Liuetal.,2014;Yao namingandoccurrencetime(CarrivickandTweed,2016)needtobe
etal.,2014),Nepali(Bajracharyaetal.,2008;ICIMOD,2011),andIndian verifiedandpreferablyunified.Alltheaboveissuesimplythatthere-
Himalayas(DurgaRaoetal.,2014;Dasetal.,2015)fromliterature, portedGLOFsshouldbefurthervalidated.Theexistingliteraturehow-
mediareports,andremotesensingdata.However,asmostGLOFsoc- ever lacks a systematic inventory of GLOFs across the entire
curredinremoteandlessinhabitedregions,lowdataavailabilityor Himalayas,suchasoutburstlakes'pastcondition,currentstatus,future
quality can cause substantial misunderstandings, especially for the projection,andtheirchronologicalcharacteristics.
GLOFeventsthathappenedpriortotheeraofsatelliteremotesensing. AnaccessibleonlinedatabaseofGLOFs,suchasproposedbyVilímek
ThedefinitionofGLOFintheHimalayasisstillunderdebate.Forexam- etal.(2014),makesasignificantcontributiontofacilitatinghazardas-
ple,somescholarsarguethatadebrisflowthatoccurredon10Aug. sessmentandriskmanagement.Aneffectivemoderntooltomonitor
2007inConaCountyisaGLOFevent(Yaoetal.,2014).However,the andanalyzethehistoricalGLOFsinthelessaccessiblehighmountain
originalreferencefocusedonthecausesandpreventioncountermea- areasisprovidedviasatelliteremotesensing,especially,theuseofopti-
suresofthedebrisflowhazard(Moetal.,2008).Wesupporttheorigi- calimagessuchastheLandsatimageswithlongarchivalrecordssince
nalauthorsinthatthiseventwasadebrisflowhazardinducedbyheavy 1972.Geomorphicevidence,e.g.,V-shapedtrench,hugedebrisdeposits,
rainfallratherthanaGLOF.Somestudiesdidnotprovidedetailedspatial anddevastatedriverbedsinaccordancewithremotesensingdata,has
locationsofthoselakes(e.g.,longitudeandlatitude);thusreadersdo beenemployedtoidentifyhistoricaloutburstevents(Komorietal.,
notknowwheretheGLOFsexplicitlyoccurred(XuandFeng,1989; 2012).Thesefeatures,however,couldalsobeformedinothercryo-
ICIMOD,2011;Falátková,2016).Otherstudiesevenreportedwronglo- hydrologiceventsratherthanGLOFs.Therefore,cautionmustbepaid
cationsofcertainGLOFevents,suchastheJincoevent(Bajracharya whenusingsatelliteobservationsalonetoidentifyaGLOFevent.A
etal.,2008;ICIMOD,2011;Liuetal.,2014),whichwaslatercorrected morerigorousmethodforGLOFverificationsrequeststhesynergyof
byYaoetal.(2014)toYindapuco.SomesameGLOFeventshavebeen multisource evidence, such as historical documents, field surveys,
assignedbydifferentcoordinates,suchastheDegacoevent(Liuetal., long-termsatelliteobservations,andhighresolutionimagearchives
2014;Yaoetal.,2014).Anotherstudy(Komorietal.,2012)confused (e.g.,GoogleEarth)thatcanbetterrevealthehydrogeomorphicpro-
theDegacoeventinLuozhaCountywiththePogeTshoeventon23 cessesinducedbydifferentGLOFincidentsacrosstheHimalayas.
July 1972 in Suoxian County. An outburst event in 2001 based on ToimproveourunderstandingofGLOFsintheHimalayas,thisstudy
multitemporalsatelliteobservationsandourfieldinvestigationwas aimsto(i)constructanup-to-dateGLOFdatabaseacrosstheentire
named to Longjiu Tsho (Yao et al., 2014) or Chongbaxia Tsho (Liu Himalayas;(ii)identifymissingGLOFeventsanddistinguishbetween
etal.,2016)on6Aug.2000,whichwaspreviouslyreferredtoas‘un- persuadableandunpersuadableeventsusingacombinationofremote
known’during2000–2001(Komorietal.,2012).Suchinconsistent sensing and geomorphological analyses;and(iii) reveal thestates,
Y.Nieetal./Geomorphology308(2018)91–106 93
characteristicandrecentchangesofoutburstlakes,includingtheirtrig- 3.2.GLOFeventsbefore1990
gersanddamages.
Atotalof32GLOFeventsoccurredbefore1990andwerebelievedto
bepersuadableaccordingtoourverificationmethods.MostGLOFsoc-
2.Methods curredatelevationsabove4200m.Fourteenoutof32eventshaveex-
plicitfloodingdateswhileothersdonot(Table1).
WeherecompiledadatabaseofhistoricalGLOFsintheHimalayas Meanwhile,sevenGLOFeventswerevalidatedtobeunpersuaded
basedonscientificliterature,reports,medianews,andassessmentsof andthusrecommendedtobeexcludedfromthehistoricalGLOFlist.
glaciallakechangesusingarchivalremotesensingobservations(see TheseGLOFevents,i.e.,BarunKholaWest,BarunKholaEast,Chokarma
referencesinTable1andTableS1).Collectedprimaryattributesfor Cho,Unnamed1st,Unnamed2nd,Unnamed3rd(Bajracharyaetal.,
eacheventincludetheoutburstlake'sname,location(region,country, 2008) and Huang Tsho (Komori et al., 2012), were previously
andcoordinates),waterlevelandareabeforeoutburst,recentarea(in misidentifiedasGLOFsprimarilyusingsatelliteimagesoraerialphoto-
2015),outburstdate,persuadability,triggers,loss/damages,andarea graphs(ICIMOD,2011;Komorietal.,2012).Inadditiontotheunknown
trend.Notallpropertieswereavailableforsomeevents,especiallyfor outburstdatesanddamage,theterminalmorainecollapseswerelikely
thoseearlierones. causedbydrainage;anddirectevidencefortheseGLOFeventsislargely
Wethendeterminedtheexactcoordinatesofthesourceglaciallake unpersuadable.
in each compiled event. Many events missed location information,
whileotherswereassignedwitherroneouscoordinates.Undersuchcir- 3.2.1.BarunKholaWestandEast
cumstances,welocatedthesourceglaciallakesbycomparingstudies ForBarunKholaWest(Fig.4A),brieflydescribedonlybyICIMOD,la-
forthesameeventorlogicalreasoningfromgeographicdescription custrinedepositioncausedbylakelevelfluctuations,cleanV-shaped
andspatialdistributionofglaciallakesandtheirsourceglaciers. breach,anddebrisfanwerenotobservedinhighresolutionsatellite
Next,wevalidatedeacheventusinggeomorphologicalanalysisand images.IfaGLOFhadoccurred,thefloodwouldhavedevastatedthe
remotesensingobservations.Geomorphologicalpropertiesincluding downstreamriverbedsfromthecollapseddam.However,tinyand
thecharacteristicsofhydrologicalbasinssuchasarea,drainagenet- crookedriversseemedtobenaturallyformedwithoutanydrasticdam-
works,slope,appearanceoflakesandglacierswerepreliminarilyana- ages.ForBarunKholaEast(Fig.4B),notrailofterminalmorainecollapse
lyzed for the possibility of GLOFs, and then followed by visual fromthislakewasobserved.Adebrisfananditsupperprovenanceare
interpretationofgeomorphicfeaturesaroundeachglaciallakeinre- clear;however,thisgeomorphicfeatureismorelikearainfall-induced
motesensingimages,suchasV-shapedtrench,debrisfan,devastation landslide. From Barun Khola East (snow-covered in Fig. 4B) to the
downstreamorlacustrinedeposition.Inaddition,areachangesforall breach(~1.4km),nodevastationevidencewasobserved.IfthisGLOF
reportedlakeswerealsomonitoredbymulti-temporalsatelliteimages. hadoccurred,avanishedlakebasinwouldhavebeenvisibleinthe
High-resolutionGoogleEarthimageryincombinationwithGlacierIn- proglacialarea.Nevertheless,nogeomorphologicaltraceindicatedthe
ventoryData(Armstrongetal.,2011;Guoetal.,2015)wereemployed existenceofanoutburstlake.
toidentifythegeomorphologicalevidenceforeachhistoricalGLOFsuch
asV-shapedtrenchanddebrisfan.Theidentifiedimpossibleevents 3.2.2.ChokarmaCho
wereclassifiedasunpersuadable. ChokarmaCho(Fig.4C),locatedbetweenLhotseGlacierandLhotse
Owingtolimitedavailabilityofsatelliteimagerybefore1990,pre- SharGlacier,wasalateralmoraine-dammedlake(closetoImjaLake)
1990GLOFeventswereprimarilyverifiedbyliteraturereviewandgeo- anddesiccatedbefore1975(theearliestavailableLandsatobservation).
morphologicalcharacteristicsinterpretedfromimageriesacquiredaf- Anunpavedfootpathpassingthislakewasobviouslyseenfromthe
terward, including V-shaped trench, debris fan, devastation GoogleEarthimageryacquiredon3Dec.2016,butdevastationdown-
downstream,andlacustrinedeposition.Post-1990GLOFeventswere stream and V-shaped breaches that indicate dam failure were not
verifiedbyarchivalLandsat5–8imageries,GoogleEarthimages,and visible.
insituphotographicinvestigations.Theprimaryevidenceincludesob-
viousshrinkageofthelakeareaandconsequentfloodsedimentation 3.2.3.Unnamed1st,Unnamed2nd,andUnnamed3rdevents
bycomparingimageriesbeforeandafterreportedoutbursts.Totrack The knowledge available on the three anonymous events,
the dynamics of glacial lakes after outburst, all source lakes were i.e.,Unnamed1st,Unnamed2nd,andUnnamed3rd,isverylimited.
mappedusingavailablearchivedLandsatimagesuntilpresent. TheUnnamed1steventwaslabeledas12Ninadistributionmapof
Finally,weinspectedallrapidlyshrinkingordisappearedglacial NepaleserecordedGLOFs(ICIMOD,2011),whichwassupposedtoorig-
lakes≥0.05km2toidentifyaGLOFusingtheHimalayanglaciallakein- inatefromamoraine-dammedlake(Fig.4D).Theindicatedlakewas
ventories(Nieetal.,2017)atfiveepisodes(1990,2000,2005,2010, dammedbythedownstreammoraineofanotherglacier,whichwassta-
and2015)withaminimummappingunitofnineLandsatpixelsor blebetween29Oct.1976and28Sep.2015.Geomorphologicalanalysis
0.0081km2.AnumberofunreportedGLOFswereidentifiedandlabeled fromhighresolutionimagesclearlyindicatedthatthedepositionfan
asnewlyfoundGLOFevents. wasoriginatedfromaglacierontheupperleftsideofthewatershed
ratherthanthelake12N.Theabovegeomorphologicalcharacteristics
donotsuggestthatthe12NhaslikelyexperiencedaGLOFthusfar.
3.HistoricalGLOFeventsacrosstheHimalayas TheUnnamed2ndevent(marked13NintheICIMOD,2011report)
isalsoimpossiblebecauseoflackofanyGLOFgeomorphicfeatures
3.1.DistributionofGLOFeventsintheHimalayas (Fig.4E).ThelocationoftheUnnamed2ndlakewasfullycoveredby
glaciericeintheLandsatimageacquiredon29Oct.1976.Aglacial
Atotalof62GLOFeventsinitiatedfrom56glaciallakes(Figs.1and2, lakewasobservedon19Oct.1988withanareaof0.05km2andgradu-
Table1)intheHimalayaswereverified,includingthreenewlyidenti- allyincreaseduntil2013.Then,asuddenexpansionoccurredin2014,
fied events in this study. All GLOF events were classified into andthelakeareareached0.23km2on28Sep.2015.Theevolutionof
unpersuadable (11) and persuadable events (51). The persuadable thislakeanditsunhindereddrainagesystemstronglyimplyalowpos-
eventswereprimarilylocatedin theeastern(26)andcentral(25) sibilityofahistoricalGLOFevent.Therecentlyrapidexpansionofthis
HimalayasoradministrativelyinChina(28),Nepal(8),Bhutan(13), glaciallakeisstoringmassivewatervolumethatcouldpossiblycause
andIndia(2).Theirelevationsrangedfrom3669to5527mwitha considerabledamageincaseofoutburst.Thislakedeservesclosemon-
meanof4831m(Fig.3). itoringinthefuture.
94 Y.Nieetal./Geomorphology308(2018)91–106
Table1
HistoricalGLOFeventsintheHimalayas(pleaseseeTableS1forcompleteattributes).
Order Name Persuadability Dateof Location Reference
outburst
1 Taraco Yes 1935-8-28 CHN XuandFeng,1989;Chenetal.,2007;Bajracharyaetal.,2008;ICIMOD,2011;
Liuetal.,2014
2 QiongbihemaTsho Yes 1940-7-10 EHS XuandFeng,1989;Bajracharyaetal.,2008;ICIMOD,2011;Liuetal.,2014;
Gurungetal.,2017
3 Lureco Yes 1950s EHN Tongetal.,2013;Yaoetal.,2014
4 SangwangTsho Yes 1954-7-16 EHN XuandFeng,1989;Bajracharyaetal.,2008;ICIMOD,2011;Liuetal.,2014
5 AlakeonCuoalongGlacier Yes 1955–1966 EHN Komorietal.,2012
6 TarinaTsho Yes 1957 EHS GeologicalSurveyofBhutan,1999;Bajracharyaetal.,2008;ICIMOD,2011;
Komorietal.,2012
7 AlakeonLunanaGlacier Yes 1960s EHS GeologicalSurveyofBhutan,1999;Komorietal.,2012
8 Cirenmaco1st Yes 1964 CHS XuandFeng,1989;Chenetal.,2007;Bajracharyaetal.,2008;ICIMOD,2011;
Liuetal.,2014;Gurungetal.,2017
9 LongdaTsho Yes 1964-8-25 CHN XuandFeng,1989;Bajracharyaetal.,2008;ICIMOD,2011;Liuetal.,2014;
Gurungetal.,2017
10 Gelhaipuco Yes 1964-9-21 CHN XuandFeng,1989;Bajracharyaetal.,2008;ICIMOD,2011;Liuetal.,2014;
Gurungetal.,2017
11 Unnamed4th Yes 1966–1974 EHS AgetaandIwata,1999;Komorietal.,2012
12 Ayaco Yes 1968-8-15 CHN XuandFeng,1989;Bajracharyaetal.,2008;ICIMOD,2011;Liuetal.,2014
13 Ayaco Yes 1969-8-17 CHN XuandFeng,1989;Bajracharyaetal.,2008;ICIMOD,2011;Liuetal.,2014
14 Ayaco Yes 1970-7-12 CHN XuandFeng,1989;Bajracharyaetal.,2008;ICIMOD,2011;Liuetal.,2014
15 NareLake Yes 1977-9-3 CHS Mooletal.,2001;Kattelmann,2003;Bajracharyaetal.,2008;ICIMOD,2011;
Gurungetal.,2017
16 NagmaPokhari Yes 1980-6-23 CHS Mooletal.,2001;Bajracharyaetal.,2008;ICIMOD,2011
17 Zharico Yes 1981-6-24 EHN XuandFeng,1989;Bajracharyaetal.,2008;ICIMOD,2011;Yaoetal.,2014
18 Cirenmaco2nd Yes 1981-7-11 CHS XuandFeng,1989;Chenetal.,2007;Bajracharyaetal.,2008;ICIMOD,2011;
Liuetal.,2014;Gurungetal.,2017
19 Yindapuco Yes 1982-8-27 CHN XuandFeng,1989;Bajracharyaetal.,2008;ICIMOD,2011;Liuetal.,2014
20 DigTsho Yes 1985-4-4 CHS Mooletal.,2001;Bajracharyaetal.,2007,2008;ICIMOD,2011;Gurungetal.,2017
21 Chhubung Yes 1991-7-12 CHS Mooletal.,2001;Bajracharyaetal.,2008;ICIMOD,2011;Wangetal.,2012;
Westobyetal.,2014b
22 UpperLangbuTsho Yes 1992 CHS Thisstudy
23 ZanglaTsho Yes 1994 CHN Thisstudy
24 LuggyeTsho Yes 1994-10-7 EHS Fujitaetal.,2008;Bajracharyaetal.,2008;ICIMOD,2011;Gurungetal.,2017
25 Xiaga Yes 1995-5-26 EHN Lietal.,1995;Yaoetal.,2014
26 Zanaco Yes 1995-6-7 CHN Bajracharyaetal.,2008;ICIMOD,2011;Yaoetal.,2014
27 KongyangmiLaTsho Yes 1997 EHS Thisstudy
28 GangriTshoIII Yes 1998 EHS Komorietal.,2012
29 TamPokhari Yes 1998-9-3 CHS Mooletal.,2001;Kattelmann,2003;Bajracharyaetal.,2008;ICIMOD,2011;
Gurungetal.,2017
30 ChongbaxiaTsho Yes 2001 EHN Komorietal.,2012;Yaoetal.,2014;Liuetal.,2016;Thisstudy
31 Jialongco1st Yes 2002-5-23 CHS Chenetal.,2007;Liuetal.,2014
32 Jialongco2nd Yes 2002-6-29 CHS Chenetal.,2007;Liuetal.,2014
33 AsupraglaciallakeofTshojoGlacier Yes 2009-4-29 EHS Komorietal.,2012
34 Geiqu Yes 2010 CHN Yaoetal.,2014
35 ChoradariLake Yes 2013-6-17 CHS Dasetal.,2015;DurgaRaoetal.,2014
36 AsupraglaciallakeofLotseGlacier Yes 2015-5-25 CHS Rounceetal.,2017
37 LemthangTsho Yes 2015-6-28 EHS Gurungetal.,2017
38 AsupraglaciallakeofLotseGlacier Yes 2016-6-12 CHS Rounceetal.,2017
39 GongbatongshaTsho Yes 2016-7-5 CHS BhoteKoshiPowerCompanyPrivateLimited(BKPC)www.bhotekoshi.com.np;Thisstudy
40 Machhapuchhre Yes 450yearsago CHS Mooletal.,2001;Bajracharyaetal.,2008;ICIMOD,2011
41 ChubdaTsho Yes Before1956 EHS Komorietal.,2012
42 TarikhaLake Yes Before1956 EHS Komorietal.,2012
43 Degaco Yes Before1966 EHN Komorietal.,2012;Thisstudy
44 JhomohariSouth Yes Before1966 EHS Komorietal.,2012
45 JichudrakeNorth1st Yes Before1966 EHN Komorietal.,2012
46 JichudrakeNorth2nd Yes Before1966 EHN Komorietal.,2012
47 SimdongGoiTsho Yes Before1966 EHS Komorietal.,2012
48 Unnamed5th Yes Before1966 EHS Komorietal.,2012
49 UpperChokhamTsho Yes Before1966 EHS AgetaandIwata,1999;Komorietal.,2012
50 UpperJiejiuTsho Yes Before1966 EHN Komorietal.,2012
51 UpperShegongTsho Yes Before1966 EHN Komorietal.,2012
52 BarunKholaEast No – CHS Bajracharyaetal.,2008;ICIMOD,2011
53 BarunKholaWest No – CHS Bajracharyaetal.,2008;ICIMOD,2011
54 ChokarmaCho No – CHS Bajracharyaetal.,2008;ICIMOD,2011
55 HuangTsho No – EHN Komorietal.,2012
56 Unnamed1st No – CHS Bajracharyaetal.,2008;ICIMOD,2011
57 Unnamed2nd No – CHS Bajracharyaetal.,2008;ICIMOD,2011
58 Unnamed3rd No – CHS Bajracharyaetal.,2008;ICIMOD,2011
59 Degaco No 2002-9-18 EHN Liuetal.,2014;Yaoetal.,2014
60 KabacheLake No 2003-8-15 CHS Bajracharyaetal.,2008;ICIMOD,2011
61 KabacheLake No 2004-8-8 CHS Bajracharyaetal.,2008;ICIMOD,2011
62 Zhemaico No 2009-7-3 EHN Liuetal.,2014;Yaoetal.,2014
Notes:CentralHimalayaNorth(CHN),CentralHimalayaSouth(CHS),EasternHimalayaNorth(EHN),andEasternHimalayaSouth(EHS).
Y.Nieetal./Geomorphology308(2018)91–106 95
Before 1990: Repeated outburst:
32 (29) Ayaco (triple), Cirenmaco
Repeated outburst:
Disappeared:
A supraglacial lake of
Persuadable: Repeated outburst: 12 (11)
After 1990: Lotse Glacier
51 events 19 (17) Jialongco, A supraglacial
lake of Lotse Glacier
(46 lakes) Expanding: Repeated outburst:
9 (7) Cirenmaco, Jialongco
Before 1990: Stable: Repeated outburst:
7 (7) 30 (28) Ayaco (triple)
After 1990: Repeated outburst:
4 (3) Kabache Lake
Fig.2.Outburstnumbersofeventsandlakesforeachscenario.
AsharpoutletanddebrisfanassociatedwiththeUnnamed3rd geomorphologicalanalysis.NeitherdoesadebrisfanrelatedtoaGLOF
event(markedas14NintheICIMOD,2011report)mightappearthere- eventexistgivenourmeticulousinspectionfromfieldinvestigations
sultofaGLOF.Theareaofthisriverbasinis~2.0km2,whichwasusually andsatelliteimages.Althoughwehaveconfirmednopreviousoutburst
coveredbysnowbasedonsatelliteobservations(Fig.4F).Thelackof ofHuangTsho,thislakeshouldbecloselymonitoredinthefutureowing
highqualityimageslimitsourcapabilitytoconfirmwhetheralake toitshighrisk(Wangetal.,2012).Itexpandedrapidlyfrom1991(1.04
formedandoutburstoccurredinthepast.However,theGLIMSglacier km2)to2015(1.78km2).Currently,aV-shapedtrenchformedatthe
inventorybasedona1966referencemapdidnotshowaglacierin outlet,andtheelevationdifferencefromthelakeleveltothedown-
thisbasin(Fig.4G).Steepbasintopographywasalsonotfavorableto stream river bed was N100m. In case of failure, outburst flooding
formalake.WebelievethatthisUnnamed3rdeventisnotpersuadable fromHuangTshomaycausecatastrophicdamagestothedownstream
basedontheaboveevidence. regionsbecauseofitshighpotentialfloodvolume(Fujitaetal.,2013).
3.2.4.HuangTsho 3.3.GLOFeventsafter1990
AnoutburstfloodfromHuangTshowasfirstreportedbyKomori
etal.(2012)basedona1966Coronaphoto.Theydescribedthattheout- 3.3.1.NewlyfoundhistoricalGLOFevents
burstfloodoccurredbefore1966byoverflowingfroma400-m-wide WeidentifiedthreepreviouslyundocumentedGLOFevents(Fig.5).
moraine dam on the right side. The lake water currently outflows ThefirstGLOFevent(86.447217°E,27.929294°N)islocatedwithinthe
throughtheleftsideofthemorainewithoutaclearV-shapedvalley SunKosiwatershedandatthetownofRongxia,Tibet,China.Theasso-
(Komorietal.,2012).However,thisGLOFeventhasneverbeenre- ciatedlake,UpperLangbuTsho,isnamedaftertheclosestLangbuTsho
portedorrecorded.WecarriedoutafieldinvestigationontheHuang withthesamemotherglacier(GLIMSglac_idofG086454E27926N).
TshoinOctober2016toverifytheGLOFevent(Fig.4H).Ourobserva- Basedonacontinuoussatellitetrackingofthisglaciallake(Fig.4A),
tionsshowthattheso-calledbreachoftheGLOFattherightlateralmo- theoutburstdatewasbetween22Sep.1992and17Nov.1992.The
raineisprobablyaphysicalresultofgravitatederosion(Fig.4I).Several lakeareaincreasedrapidlyfrom0.06km2in1989to0.24km2on22
gulliesareclearovertheunstablelateralmoraineinthephotographs, Sep.1992,followedbyasharpshrinkageaftertwomonthson17Nov.
whichwerepossiblycausedbyprecipitation,meltedsnow,and/orbur- 1992 (0.06km2), and then remained relatively stable until 2015.
iedice.Theheadpartofthelargestgullyisjustabout40mwide,and Thelakewasconnectedtotheglacierterminusbeforeitsoutburstin
this gully is ~350m long, which seems to bea trench from Huang 1992anddetachedafter2009(Fig.5AandD).Iceavalanchepossibly
Tsho(Fig.4JandK).Butactually,thehighestlakelevelneverreached triggered this GLOF given a steep ice cliff and a rapid retreat of
the head of this gully in accordance with the photographic and theglacier.
The second GLOF event (82.118101°E, 30.355574°N) is located
withintheMaquanRiverbasin,Tibet,China.ThislakeisentitledZangla
TshoinaccordancewiththedownriverZanglaqu.Satelliteobservations
suggestthatZanglaTshoGLOFoccurredbetweenAprilandOctoberin
1994(Fig.5BandE).ZanglaTshokeptstablebetween10Oct.1988
and27Dec.1993withanareaof0.21km2andrapidlyshrunktoa
verysmalllake(0.01km2on27Oct.1994)aftertheoutburst.Lacustrine
depositionisclearlyobservedinahighresolutionimageon2Dec.2005.
Thelakewasalreadydisconnectedfromitsupstreamglacier(GLIMS
glac_idofG082129E30336N)in1988byatleast~400m.Thecleangla-
cierupstreamretreatedfastfrom1988to2015.Thetrailoflandslideor
rockfallisnotobservedaroundtheglaciallake.Aglaciallakewaslo-
cated atthe upstream tributary andshrunk by 17.6%from 27 Dec.
1993to27Oct.1994.Drainagefromthislaketothefloodeddown-
streamlakeappearsevidentinthehighresolutionimage(Fig.4E).
Thewaterinflowfromtheupstreamlakelikelycausedthedamfailure
ofthedownstreamlakeandtriggereditsoutburstflood.
Thethirdevent(KongyangmiLaTsho,88.782077°E,27.901247°N)is
locatedinTistabasinandoccurredbetweenAprilandOctoberin1997
(Fig.5CandF).Thislakewas0.24km2on14June1990,expandeddra-
maticallyto0.55km2on8Nov.1991,andgenerallystabilizedbetween
1991and1996.Aftertheoutburstin1997,theglaciallakeremainedsta-
Fig.3.AltitudinaldistributionsofHimalayanhistoricalGLOFevents. bleuntil2015(~0.28km2).Thefrontaledgeofthisglaciallakeretreated
96 Y.Nieetal./Geomorphology308(2018)91–106
Fig.4.GeomorphiccharacteristicsneartheunpersuadableGLOFeventsbasedonGoogleEarthimages(A–H)andinsituphotos(I–K).
byN200maftertheoutburstcausedbythelakeleveldrop.Theleft lakewasconnectedtotheWenjiaGlacier(Fig.6C).Nogeomorphological
trailingedgeofthisglaciallakeretreatedbyN120mandadvancedde- evidencecouldbefoundfromremotesensingimagerytoverifyaGLOF
positionasaresultofupstreamiceavalanche.Itismostlikelythatanice nearthislake.WethereforeconcludethatthereportaboutthisGLOF
avalancheoccurredontheleftsideofthemainglacier(GLIMSglac_idof eventinLiuetal.(2014)isquestionable.
G088819E27930N) and that the mass movement of the ice Inanotherstudy,researchersthoughtthatDegacowaslocatedat
avalancheplungedintotheglaciallake(Fig.2F),whichtriggeredthis 28.33°N,90.67°EaccordingtoliteraturedescriptionsandGoogleEarth
GLOFevent. images,whichburston18Sep.2002(Yaoetal.,2014).Thislocationof
DegacowasthesameasanotherGLOFeventcalledPogeTshothat
3.3.2.Corrected/updatedGLOFevents wasbelievedtooccurbefore1966inaccordancewithaCoronasatellite
Erroneousgeographiccoordinatesoroccurrencetimesaremislead- photo(Komorietal.,2012).WeagreewithKomorietal.(2012)thatthis
ingandpreventresearchersfromunfoldingtheprocessormechanism lakeburstbefore1966(asshowninFig.5D).However,Komorietal.
ofaGLOFevent.Thisstudycorrectsorupdatesthepreviouslyreported namedthislakePogeTshobecauseoftheGLOFeventin1972reported
characteristicsofthefollowinghistoricalGLOFevents. byXuandFeng(1994).Otherstudies(XuandFeng,1989,1994;Liu
etal.,2014;Yaoetal.,2014)havedemonstratedthatPogeTshowaslo-
3.3.2.1.Degaco.Degaco(Fig.6)wasfirstreportedtobelocatedinLuoza catedinSuoxianCounty(notinLuozaCounty),whichcausedafloodon
County(28°07′25″N,90°34′01″E)(Liuetal.,2014)whereapro-glacial 23July1972.Wehereverifythatthecorrectnameofthislaketobe
Y.Nieetal./Geomorphology308(2018)91–106 97
Fig.5.Landsatobservationsoflakedynamics(A–C)andgeomorphiccharactersfromGoogleEarthimages(D–F)forthethreenewlyfoundGLOFevents.
DegacoaslabeledinGoogleEarthandTiandituprovidedbytheNational 3.3.2.2.ChongbaxiaTsho.AccordingtoKomorietal.(2012),ananony-
AdministrationofSurveying,MappingandGeoinformation,China.Did mouslakewasobservedtoexperienceanoutburstfloodfromLandsat
thislakebursttwice(i.e.,before1996andin2002)?Theanswerisno imagesacquiredbetween17Nov.2000and20Nov.2001(Komori
givenourinterpretationofarchivalimageryandfieldsurvey.Evident etal.,2012).Otherstudies(Yaoetal.,2014;Liuetal.,2016)thought
downstreamsurfacedamagewasnotobservedinimagesacquiredbe- thatthiseventoccurredon6Aug.2000.Thesourcelakeofthisevent
tween2000and2002(Fig.6A).Areasofthislake(~1.12km2)remained wascalledasLongjiuTshoinYaoetal.(2014)andChongbaxiaTshoin
stablefrom2000to2015.Thefreshgravelsandsandsontheolddebris Liu et al. (2016). Our analysis confirms thatthis event occurred in
fanstaysimilarinthephotostakenin1966andin2016(Fig.6DandE). 2001basedonarangeofLandsatobservations,specificallybetween
Atthispoint,theoriginalglaciallakethatcausedafloodon18Sep.2002 5Feb.and4Nov.2001(Fig.7A).AGLOFeventisusuallynamedafter
cannotbeconfirmed.Thus,weverifythataGLOFinDegacomightonly its initial outburst lake. Therefore, we here name this event as
occurbefore1966. ChongbaxiaTshooutburstflood(Fig.7B).
98 Y.Nieetal./Geomorphology308(2018)91–106
Fig.6.UpdatingthecharacteristicsofDegacoGLOFeventusingLandsatimages(A),GoogleEarth(B,C),photos(D)modifiedfromKomorietal.(2012)andourfieldphoto(E).
3.3.2.3.Geiqu.TheoutburstfromLakeGeiquwasfirstreportedbyYao becauseofasuccessfulimplementationofanearlywarningsystem
etal.(2014)basedontheirfieldsurveysin2009and2011.Thelake (Gurungetal.,2017).
areabeforeoutburstwasestimatedtobe0.05km2,andtheoutburstoc- ThelocationofthiseventwasfirstidentifiedbytheJapanAerospace
curredbetween24Juneand28July2010usingHuanjing(HJ)1A/Bim- ExplorationAgency(JAXA)inashorttimeusingPhasedArraytypeL-
agery, which was possibly triggered by intensive precipitation or bandSyntheticApertureRadar-2(PALSAR-2)dataandAdvancedLand
outflowfromtheupperlake(Yaoetal.,2014).Wehereprovideaddi- ObservingSatelliteimagery(Nagaietal.,2016).JAXAsharedtheirdoc-
tionalremotesensingevidencetosupportthiseventasaV-shaped umentandlakeextentdataontheirwebsite(http://www.eorc.jaxa.jp).
breach,freshdebrisdeposit,anddestroyedroadswereclearlyobserv- LamthangTshowasbelievedtoundergoaremarkableexpansionfrom8
ableinFig.7CandD.Thedamageofthiseventwasminorfromitslim- Mar.to23Apr.2015andaremarkableshrinkagefrom23Apr.to2July
itedfloodingvolume.Twoglaciallakesareobservedinthisbasin.One 2015(Nagaietal.,2016).However,long-termLandsatobservations
lakehasacliffyedge(~70mhigh)andwasconnectedtoaglacierup- showthatLemthangTshoshrankfrom24Dec.1987to8Mar.2015,al-
stream,whiletheotherwasmoraine-dammedanddisconnectedfrom thoughthelakesizeremainedrelativelystablebetween1989and2015
theglacier.Glacierswithatotalareaof3.18km2weredistributedin (Fig.8)withanaverageareaof0.055km2.Fromanotherstudy(Gurung
theupriverbasin.Thehorizontaldistancebetweenthesetwoglacial etal.,2017),apicturetakeninMay2015showsthatLemthangTshoex-
lakesis340m.Thedownstreamglaciallakewaslabeledastheinitial hibitedanormalextentcomparedwithLandsatextractedwaterextent
outburstlakeinYao'setal.(2014)study. beforetheGLOF.AnotherpicturedemonstratesthatLemthangTshodis-
appearedinlateJuly2015(Gurungetal.,2017).Suchevidencereveals
3.3.2.4. Lemthang Tsho. A GLOF event on 28 June 2015 from the thatLemthangTsho'schangeswereverycomplex.
LemthangTsho(alsoknownasMemariTsho)wasreported(Orlove,
2016;Shresthaetal.,2016).Thisfloodwashedawayseveralbridges 3.3.2.5.OutburstofasupraglaciallakeonTshojoGlacier.Komorietal.
andcausedsomemajorlandslidesdownstreambutwithoutanyfatality (2012)reportedasupraglaciallakeoutburstcaseassociatedwiththe
Y.Nieetal./Geomorphology308(2018)91–106 99
Fig.7.UpdatingtheChongbaxiaTshoandGeiquGLOFeventsusingLandsat(A)andGoogleEarthimagery(B–D).
TshiojoGlacieron29Apr.2009.Thiseventdidnotcausemuchdamage lakesintheredboxofFig.9A,intersectedwiththewatersurfaceof
becauseofitslimitedfloodvolumeof500thousandm3recordedata thesupraglaciallakeson24Apr.2009,rapidlyfluctuatedfrom1988to
hydrologicalgaugeinthePhoChuRiver.Floodwaterwassupposedto 2015;andabruptshrinkageofthesesupraglaciallakeswasobserved
bedrainedfromasupraglaciallakeonthelowerpartoftheTshojoGla- atleasttwiceonthesamepartoftheTshojoGlacier(Fig.9B).Thisfluc-
cier,accordingtofieldsurveyandsatelliteimages(Fig.9A).Thestudyof tuationrevealsthecomplexityofsupraglaciallakeevolutionprocesses.
Komorietal.(2012) posedahypothesisthatleakingwaterofthat GLOFsresultingfromsupraglaciallakesalwayshaveacloserelationship
supraglaciallakegushedoutatthelowerendoftheTshojoGlaciervia withenglacialorsubglacialdrainagesystemsfortheirlimitedwatervol-
englacial or subglacial channels and formed some sand and gravel ume.Thisimpliesthatthewholeprocessofanoutburstoriginatedfrom
moundsaswellasanontypicaldebrisfanaroundtheoutlet(Komori a supraglacial lake via englacial and subglacial drainage systems is
etal.,2012). rathercomplexandstillneedstobefurtherexplored.
Changesofsupraglaciallakesfromspillwayorcoalescence,includ-
ingseasonalemergence,disappearanceandexpansion,canbehighly 3.3.3.UnpersuadableGLOFevents
dramaticintheHimalayas(Bennetal.,2001;Gardelleetal.,2011; Fourpost-1990floodeventsfromKabacheLake(Bajracharyaetal.,
Watsonetal.,2016;Nieetal.,2017).Thetotalareaofsupraglacial 2008; ICIMOD, 2011), Degaco (analyzed in Section 3.3.2.1) and
Fig.8.ArealchangeoftheLemthangTshousingLandsatimages(between24Dec.1987and8Mar.2015)andPALSAR-2data(23Apr.2015).
100 Y.Nieetal./Geomorphology308(2018)91–106
Fig.9.LocationobservedfromGoogleEarth(A)andarealchange(B)offloodedsupraglaciallakesontheTshojoGlacier(redbox).
Zhemaico (Liu et al., 2014; Yao et al., 2014) were verified to be ofmorainecollapsewithoutanydamage(ICIMOD,2011).Although
unpersuadableGLOFs. exactlatitudeandlongitudecoordinateswerenotprovidedinthereport,
KabacheLakewassuccessfullyfoundfromamapofGLOFeventsinNepal
3.3.3.1.KabacheLake.TwoGLOFeventsfromKabacheLakewerere- (Fig.10A).AnevolutionofKabacheLakeandthedamageofthedown-
portedtooccuron15Aug.2003and8Aug.2004respectivelyasaresult streamvalleywereclearlyrecordedbyaseriesofLandsatimagesfrom
Fig.10.LocationsfromGoogleEarthimages(A–C)andLandsat-derivedarealchanges(D)forKabacheandZhemaico.