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Glacial Lake Outburst Events in the Bhutan Himalayas
Jiro KOMORI1*, Toru KOIKE2, Tsutomu YAMANOKUCHI3 and Phuntsho TSHERING4
1

Graduate School of Environmental Studies, Nagoya University,
Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan(Present affiliation: Department of Modern Life, Teikyo Heisei University)
2
Earth System Science Co., LTD., Shinjuku, Shinjuku-ku, Tokyo 160-0022, Japan
3
Remote Sensing Technology Center of Japan, Roppongi, Minato-ku, Tokyo 106-0032, Japan
4
Department of Geology and Mines, Royal Government of Bhutan, Thimphu, Bhutan*e-mail: j.komori@thu.ac.jp

Abstract
Maintaining proper preparedness for GLOF hazards and drawing attention to the task of mitigation areimportant goals, necessitating exploration of past cases of outbursts. The frequency of GLOF occurrences isstill unknown, because major outbursts which cause significant damage downstream are rare and records havebeen kept on them for only the past several decades. We have to collect as much data on past outburst events
as possible, including unpublished and previously unknown incidents. As is obvious in the traces of known
GLOFs, an outburst event leaves typical topographical and sedimentological features, i.e., 1) V-shaped
trenches, 2) huge debris fan depositions and 3) subsequent devastated river beds. Hence, these features can beused as proof of past outburst events. We describe the 2009 Tshojo flood as the most recent case of a GLOF in
the Bhutan Himalayas. The flood, which was initiated by dam leakage and water splashing on the surface
from en-/sub-glacial passage, was a potentially dangerous hazard. Attention to such outburst events frominvisible sources will be required in the future.
As for evaluating the frequency of GLOF incidents, besides the six cases reported in previous studies, werevealed a total of 15 other outburst cases in the Bhutan Himalayas using field survey data; Corona KH-4A,
Hexagon KH9-9, Landsat7/ETM+, and ALOS/PRISM satellite data; and images from Google Earth. These 21
cases were found on the Tibetan branch of the Kuri Chu, and the Chamkhar Chu, Pho Chu, Mo Chu and Soe
Chu rivers. Lake outbursts at the foot of cliffs with hanging glaciers were the most frequent cases, accounting
for ten of the GLOFs. Seventeen of the 21 cases occurred before the 1970s, while four cases were counted during the period from the 1970s to 2010. Hence, the current frequency of outburst occurrences does not seem tohave increased. Further research is urged, covering minor outburst events, and the scope has to be broadened
at least to the Sikkim and Nepal Himalayas.
Key words: case study, glacier hazards, global warming, occurrence frequency, satellite data,
topographic feature

1. Introduction
Glacial lake outburst floods (GLOFs), a form ofnatural disaster, are a serious issue in Bhutan and other
Himalayan countries. Hazard mitigation work andawareness building have also been carried out in Bhutan.
Nevertheless, fundamental information related to the
GLOF issue, i.e., which rivers have hazardous conditions
and which rivers seem to be safe, and how often GLOFs
occur at present and may occur in the future, is still unclear. Fortunately, Bhutan has not experienced a severe
GLOF disaster since the 1994 Luggye flood. Even so,
previous studies have recorded six cases in the watersheds of major Bhutanese rivers (Fig. 1). In order toachieve disaster mitigation, we need a clear understandGlobal Environmental Research
16/2012: 59-70
printed in Japaning of where and how often such events have occurred in
Bhutan in the past, through clear evidence. A considerable number of studies have compiled GLOF records andtheir characteristics in the Tibet, Bhutan and Nepal
Himalayas (e.g., Yamada & Sharma, 1993; Xu & Feng;
1994). Further compilation work in this region by
Richardson and Reynolds (2000) shows the chronological frequency on the basis of a total of 33 records fromthe 1935 Tara Cho GLOF in Tibet to the 1998 Sabai Tsho
GLOF in Nepal. According to their study in the 1990s,
outburst incidents on average showed an almost biennial
occurrence and their frequency was judged to be
increasing toward the 1990s and the future. Regarding
the global warming issue, such remarks on “frequent
outbreaks” can be seen in various kinds of reports, gen©2012 AIRIES

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J. KOMORI et al.

eral journals and newspapers. However, this frequency
has not been reflected equally between the compilation
data and actual cases in the last decade or more in theregion. Such a discrepancy means it is impossible toestimate the frequency based on simple compilation ofmajor GLOF records, because such major events, e.g.,
the 1994 Luggye flood, are a rare phenomenon. On theother hand, there is a possibility that relatively minor
events have also been recorded recently due to modernization in rural areas around the Bhutan Himalayas. If theaccuracy of this record has changed over the years, theearlier studies have a problem with consistency of data.
Hence, to acquire the above mentioned “clear understanding,” further study with collection of a sufficientnumber of data is required. In this study, we show unreported small incidents which were just moraine dam
breach events without severe flooding in the lower
reaches, using field- and satellite-data-based compilation.
Furthermore, we consider the spatiotemporal tendency ofoutburst occurrences in the Bhutan Himalayas based on
our compilation and recent published information.

2. Study Area and Method
The study area of the Bhutan Himalayas is the borderregion between Bhutan and China and the Kulha Kangri
massif region on the Tibetan side (Fig. 1). This area
encompasses the upper watershed of the Jamuna(Brahmaputra) River as well as inland rivers of southern
Tibet. These rivers take their rise in the main Himalayan
range and branching ridges, at altitudes ranging from4000 to 7500 m. There are several square kilometers ofcirque glaciers and several valley glaciers of ca. 10 km2
in the headwater watersheds. Most valley glaciers on thenorthern side of the main range and the Kulha Kangri
massif simply flow to the north, whereas those on thesouthern side randomly flow to the south. The glaciers in
the Bhutan Himalayas also show distinct retreat due toglobal warming (Ageta & Iwata, 1999; Karma et al.,2003), and have many pro- and supra-glacial lakes in thesame manner as the other eastern Himalayas.
During our field surveys of some GLOF-devastatedsites in the eastern Himalayas, we witnessed gaping valleys (V-shaped trenches) and obvious debris fans at theoutwash of glaciers (noted as “V” and “F” in the photograph of Fig. 2). These extraordinary landscape features
made us realize that dam breaches had, in fact, occurredin the past. Furthermore, a bare river bed with voluminous boulders could be seen downstream along the river(“D” in the photograph of Fig. 2). These particular typesof topographies due to outbursts, especially morainedam breaches, have been described in numerous studies
as typical traces of outbursts (Gansser, 1983; Vuichard &Zimmermann,1987; Clague & Evans, 2000; Dwivedi
et al., 2000; Richardson & Reynolds, 2000; Osti et al.,2010). Satellite photographs taken in the 1960s and 70s
by US reconnaissance satellites Corona KH–4A andHexagon KH-9-9, and subsequent satellite imagery,
Landsat ETM and SPOT, have clearly and continuously
captured such particular types of topographies. On theother hand, common melt-water naturally has sufficient
force to cause erosion and deposition at the outlets andthe outwashes of glaciers and glacial lakes. However,such small streams cannot create (1) sharp and uniform
V-shaped trenches, (2) huge debris fan depositions and(3) subsequent devastated river beds. Hence, the difference between breached and non-breached moraine dams
has to be identified by the above three types of evidence

Fig. 1 Study area and locations of reported GLOF events in previous studies. Red circles and four-digit
numbers show the locations and the years of outburst occurrence. The red star indicates LuggyeTsho, which was breached in 1994. Yellow circles are the locations of outbursts of which the yearof occurrence is unknown. The blue circle is the location of the Tshojo glacier. The red letter “L”
indicates Lhedi Village. K.K. is the Kulha Kangri massif.

Glacial Lake Outburst Events in the Bhutan Himalayas

61

Fig. 2 Schematic view of the three proofs for identification of past outburst events. The
lower left photograph shows an actual case of proof of outburst from the Tarina
glacial lake.

in field surveys and satellite photographs/imagery(Fig. 2). In this article, we have extracted traces ofbreaches from satellite data and field information.

3. The Latest GLOF Event in Bhutan
Prior to illustrating the results of our selection, we
will describe an outburst case involving the Tshojo glacier in 2009, because it is the most recent event in Bhutan
and previously unreported in general.
3.1 Outline of the Tshojo flood
The Tshojo glacier is a typical debris-covered glacierand the largest glacier on the southern side of the Bhutan
Himalayas. At 3 AM on the 29th of April 2009, a basic
health unit staff member of Lhedi Village in the Lunana
region (‘L’ in Fig. 1), which is three kilometers downstream from the terminus of the Tshojo glacier, heard aroaring sound from the main Pho Chu river (“Chu”
means water or river in Bhutanese language). He subsequently observed flooding in the Gotey Chu (Fig. 3,
lower left), which comprises the outlet of the glacier andis a western tributary of the Pho Chu. This was the firstobservation of any unusual discharge from the Tshojo
glacier. Subsequently an alert from the staff was sent out
via a radio transmission and personal cell phones to citizens who lived in Punakha City, approximately 70 km
downstream, so they could keep watch on the Pho Chu.
On hearing the warning, some citizens tried to evacuatewith their belongings, because they had previous experienced a flood hazard in 1994 due to an outburst in the
Luggye Tsho in Lunana. Fortunately, however, there wasno damage, even along the murky and swollen river. This
was the first occurrence of possible trouble since the1994 GLOF. Compared with a few days earlier, a discharge meter in the Pho Chu recorded less than approxi-

mately 0.5 million m3 of flood water. This value certainlyshows a suddenly increased discharge volume from the
Tshojo glacier, because the records in the other watershedareas were static during this period.
The topographical and sedimentological evidence
which was acquired by PRISM (Panchromatic Remotesensing Instrument for Stereo Mapping) onboard the
ALOS (Advanced Land Observing Satellite) and fieldsurveys in 2009 and 2010 shows deep eroded channels on
the lower end of the glacier, and spreading debris in frontof the outlet and along the riverbed of the Pho Chu(Fig. 3A). These characteristics prove that some flood
event occurred on the lower part of Tshojo glacier.
Further sedimentological and geomorphological aspects
are as follows:
1) There are debris lobes with partly reverse-gradedsand gravel at the bottom of the newly opened widechannel (Fig. 3B).
2) The lobes overflow the bank of the channel andbushes on the glacier, as well as the junction of theGotey Chu and Pho Chu.
3) The channels suddenly vanish on the upper side.
4) Small mounds with crater-like hollows on the top
remain (sand/gravel volcanoes) at the bottom of theupper end of the channel (Fig. 3C).
5) These mounds consist of well sorted sand and finedepleted gravel sediments.
6) The sandy units show massive facies, indicating thatthe units were formed by a short-term event.
7) A fresh ice wall was exposed at the terminus of the
Tshojo glacier in 2009, whereas that part as well as
the adjacent slope was almost covered by talus debris
by 2010.
Aspects 1 and 2 prove that some debris flow occurredon the glacier. Aspects 3, 4 and 5 show that the debris
flow originated from a sand/gravel fountain with a large

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Fig. 3 Photo A: a fresh debris fan (lower center) and V-shaped trench (middle left) at the terminus of the Tshojo
glacier. The Pho Chu and Gotey Chu meet at the lower right. Photo B: 80 cm thickness of fresh debris lies on
the original ground surface. The flood sediment partly shows reverse-grading and fine-depleted fabrics. Photo
C: a sand and gravel mound near the upper end of the channel, which is a source of debris flow. A small
amount of water remains at the bottom of the funnel (middle right). Lower half: an explanatory diagram of the2009 Tshojo flood. The water conduit (blue colored channel in the diagram) is tentatively placed at the middle
depth of the ice.

amount of flood water from underground, i.e., via
englacial or subglacial channels. The well-sorted units
may have been left due to blown water in the final phaseof the flood.
3.2 Source of the flood water
Figure 3 shows the schematic sequence of the estimated model based on the above-mentioned facts inconnection with the Tshojo outburst event. In the fieldsurvey of 2010, we could find fresh traces of water
lowering in supraglacial lakes at 1.3 and 4.7 km upstream
from the glacier terminus (lakes X and Y in Fig. 3). Thesebowl-shaped depressions show that lake water had emptied in recent days. ALOS/PLISM (January 17, 2010)
satellite data also show shrinkage of these water areas.
However, the estimated volume of the empty lake ponds
is insufficient for estimating the discharge volume. We
could not obtain reliable evidence of the source of theflood water. After the field survey, a remote sensing
analysis using ALOS/ PALSAR data (March 3, 2009 andJuly 23, 2009, which are before and after the event),
showed the abrupt disappearance of a supraglacial lakewith a radius of 300 ~ 500 meters at 5.5 km upstream
from the outlet (Lake Z in Fig. 3) (Yamanokuchi et al.,2011). This lake grew abruptly after 2008 and its
area finally expanded by a factor of at least three (ca.

60,000 m2). These lakes provide strong evidence of an
outburst event as the source of the water, sand/gravel
fountains and debris flow.
A similar sudden discharge event on a debris covered
glacier has been documented in previous studies, i.e., theGLOF at the Lipmoshar glacier, central Nepal, in 1991
(Yamada & Sharma, 1993; Fujiwara & Gomi, 1995). The
1977 GLOF in Mingbo Valley, eastern Nepal, which was
described as a moraine failure (Fushimi et al., 1985), canalso be considered an outburst of a supraglacial lake on
the Nare glacier, because the source of the flood in the
1962 Corona satellite photo and recent satellite data
seems to have been in the debris-covered part of the Nareglacier rather than a proglacial lake with a moraine.
Furthermore, such expansion and shrinkage of supraglacial lakes had been well studied on the Ngozumpa
glacier, one of the biggest glaciers in the eastern Nepal
Himalayas (Benn et al, 2001).
As mentioned above, the cause of the Pho Chu floodin 2009 has been revealed to be an outburst event fromsupraglacial lakes on the Tshojo glacier. This event also
formed the topographical and sedimentological characteristics of an outburst, i.e., a V-shaped trench and debris
fan. Hence, this event is equated to past outburst events
which are featured in this study, although the scale of thedisaster was small.

Glacial Lake Outburst Events in the Bhutan Himalayas

4. Outburst Events in the Bhutan Himalayas

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Besides the six reported cases in the previous study,
15 outburst cases were found using field and satellite datain the Bhutan Himalayas. Figures 4 - 18 illustrate theseoutburst cases. Table 1 lists location data, present conditions, materials used in distinguishing outburst events,
dates of events and probable outburst triggers. The loca-

tion type "cliff foot” (e.g., Fig. 6) means the lake was
located at the foot of a steep cliff with a hanging glacier.
Such a condition is similar to that of the “proglacial lake”
type, but, this topographical condition distinctly differsfrom that of a typical proglacial lake, which is in directcontact with the glacier snout in a horizontal orientation.
Table 2 explains the impact of each outburst downstream
and gives additional information on each event.

Fig. 4 Corona satellite photo of northern Jichudrake. The widthof the photographic subject is approximately 5.5 km.

Fig. 7 Bird’s-eye view of a breached lake 3 km west of Tomo La.
The base image is copyright of Google Earth. The lengthof the lake is approximately 1.7 km.

Fig. 5 Corona satellite photo of southern Jomohari. The width ofthe photographic subject is approximately 700 m.

Fig. 8 Corona satellite photo of Simdong Goi Tsho. The width ofphotographed subject is approximately 1.5 km.

Fig. 6 Field view of the upper Chokham Tsho. Photo taken in
May 2011. The width of the moraine is approximately
500 m. The glacier ice on the steep cliff is also distinct.

Fig. 9 Corona satellite photo of a glacial lake in the northern
Gangju La pass. The width of photographed subject isapproximately 3 km.

Table 1 Outburst events in the Bhutan Himalayas (locations and determination of occurrence dates).

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Table 2 (continuation from Table 1) Outburst events in the Bhutan Himalayas (impact of flooding and remarks).

Glacial Lake Outburst Events in the Bhutan Himalayas
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Fig. 10 Corona satellite photo of a lake with Huang Tsho (right)
and Sangwang Tsho (left). The width of photographedsubject is approximately 6 km.

Fig. 13 Bird’s-eye view of the upper Jiejiu Tsho. The base image
is copyright of Google Earth. The width of photographedsubject is approximately 2 km.

Fig. 11 Field view of the outlet of Luggye Tsho. Photo taken in
September 2009.

Fig. 14 Bird’s-eye view of Upper Shegong Tsho. The base image
is copyright of Google Earth. The width of photographedsubject is approximately 2.5 km.

Fig. 12 Corona satellite photo of Poge Tsho. The width of photographed subject is approximately 2.5 km.

Fig. 15 Corona satellite photo of the Cuoalong glacier. The widthof photographed subject is approximately 12 km.

4.1 Distribution and topographical features oflake outbursts
The compiled data of past outburst cases make it possible
to discuss their spatial characteristics, i.e., GLOF prone
areas in the Bhutan Himalayas. According to the listed
cases, nineteen instances are found along the border with
Bhutan and China, i.e., the main Himalayan range (Fig.
19). Another two cases, one of an unnamed lake and theother of the Gangri III lake (index number 21 and 9 inTable 1 and Fig. 19), are located along the ridges dividing
the Kuri Chu and Chamkhar Chu, and the Pho Chu andMo Chu, respectively. Looking at individual watersheds,
the Pho Chu basin and the Tibetan side (beyond thewatershed of Bhutanese rivers) had the largest number,with five cases, followed by four cases on the Tibetanside of the Kuri Chu, three cases along the

Chamkhar Chu and two cases along the Mo Chu and Paro
Chu (Soe Chu). Despite the the presence of glacial lakes
in various other glacierised areas, there are no outburst
records in the following watersheds: Jaidakha Chu, Amo
Chu, Ha Chu, Thimphu Chu, Mangde Chu, Dangme Chu,
Nara Ama Chu and Dhansiri Chu (Fig. 1). As for variation by elevation, outburst cases are seen at altitudes from4,200 m to 5,200 m with a peak from 4,700 m to 4,900 m.
This elevation range corresponds to the major range ofglaciers existing in the Bhutan Himalayas.
We also attempted to categorize these cases according
to outburst triggers. Based on the features of the
topography surrounding the lake and its relation to theglacier ice, the 21 listed cases could be classified into thefollowing three main categories: type 1) plunging ofglacier ice down a cliff foot, type 2) glacier advance orGlacial Lake Outburst Events in the Bhutan Himalayas

Fig. 16 Field view of the outlet of Tarikha glacier. Photo taken in
July 2010. The width of the photographed subject isapproximately 500 m.

Fig. 17 Field view of the Chubda glacier. Photo taken in July
2010. The width of the moraine is approximately 600 m.

Fig. 18 Vertical view of the upper Gangri Tsho. The base image
is copyright of Google Earth. The width of thephotographed subject is approximately 1.1 km.

67

calving at the snout of a proglacial lake, and type 3) ice
deformation around a supraglacial lake. Type 1, as
represented by the cases of the 1957 GLOF at Tarina
Tsho (Fig. 2 and index No. 8 in Fig. 19) and Upper
Chokham Tsho (Fig. 6 and index No. 5 in Fig. 19), is themost common outburst condition (ten cases, 48%). These
outburst cases seem to be triggered by ice plunging into
the lake from hanging glaciers or unstable glaciers atop
cliffs. The next most common condition, with sevencases (33%), is type 2, which is represented by the case of
the Sangwang Tsho GLOF in 1954 (Fig. 10 and index No.
11 in Fig. 19). The three occurring at the headwaters ofTibetan rivers were triggered by glacier advance and/or
large glacier calving upstream of the lakes. Furthermore,
the triggers of two outbursts in proglacial lakes, Luggye
Tsho (Fig. 11 and index No. 14 in Fig. 19) and the
Cuoalong glacier (Fig. 15 and index No. 18 in Fig. 19)
seem to be a landslide and/or ice avalanche in each case
(Komori et al., 2005; Fujita et al., 2008). The triggers of
the remaining two cases are unknown. As for the third
category, two cases (10%) involving supraglacial lakes,
the Tshojo glacier flood in 2009 and the Chubda Tshooutburst appeared to be triggered by ice deformation of
one or more supraglacial lakes. The ice avalanche andcalving which were defined as the major triggers (53% of
the total) in Richardson and Reynolds (2000) correspondto the above mentioned “type 1.” On the other hand, we
could find no apparent outburst cases due to moraine
failure and collapse among these 21 cases. While there isinsufficient previous evidence, moraine failure has been
considered as a scenario for triggering a deadly GLOF at
Thorthormi Tsho in Lunana. Hence, further research andcompilation work is required concerning such categorization of lake conditions and triggers of outbursts,.

Fig. 19 Locations of the outburst events based on compilation work of the present and previous
studies in the Bhutan Himalayas. The numbers correspond to the index numbers in
Tables 1 and 2 and Fig. 20. The numbers 8, 11, 14, 18, 19 and 21 indicate recorded
events, with dates of outburst (Fig. 1) noted in Gansser (1983), Xu and Feng (1994),
GSB (1998), Karma and Taman (1999) and Komori et al.(2005). The outburst
occurrences of numbers 4, 5 and 6 were recognized by Ageta and Iwata (1999) andChiyuki Narama (personal communication in 2011 June).

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Fig. 20 Occurrence tendencies of GLOF and outburst events. A:. outburst cases in the Bhutan Himalayas (this study). B: recorded
GLOFs in the Himalayan Mountains of Nepal, Bhutan and Tibet (in previous studies).

4.2 Temporal tendencies of outburst occurrences
Ten of the 21 cases of occurrence years could be defined as between the 1950s and 2009 according to thedata of this and previous studies (Table 1). As for theremaining eleven cases, we conclude these to haveoccurred before 1966, because landscapes subsequent to
outbursts were already captured in 1966 Corona satellite
photographs in each case. These outbursts had occurredfrom the inside of moraine ridges which were most proximal to the glacier ice. Hence, the breached lakes may
have appeared after the termination of the Little Ice Age,
which is generally accepted as the middle of the 19th
century and may mark the beginning of the ongoing
period of glacier shrinkage. This means that these outburst events, especially the eleven cases the ages ofwhich are unknown, must have occurred from the middleof the 19th century to the 1960s.
Figure 20A shows the chronological distribution ofoutburst occurrences in the Bhutan Himalayas in accordance with the above evidence. The distribution clearlyshows that of all the recorded cases, 17 occurred disproportionately before the 1970s, whereas the occurrence
tendency in the last 40 years seems to have dropped orat least not increased compared to before the 1970s.
Figure 20B shows the frequency of GLOFs in Nepal,
Bhutan and Tibet, based on previous studies, to the bestof our knowledge. With reference to the most recent
event in this region, previous studies have mentioned it as
the 2003 and 2004 Kawache GLOF in the northernheadwaters of the Madi River at the southeastern foot of
the Annapurna Massif in Central Nepal (Ghimire et al.,2005; Shakti, 2009). However, according to satellite
image observations (Nov. 8, 2004 Landsat ETM; Dec. 13,
1999 Landsat ETM; and Jan. 2, 2004 SPOT ), these flood
events were not caused by lake outbursts but rather glacier avalanches, since the lake showed stable conditions at
those times and the flood marks ran down from a trace ofan avalanche on the right bank of the eastern headwatersof the Madi River. The latest event should be consideredthe 1998 Sabai Tsho GLOF in the Khumbu Himalayas.
Therefore, an increasing tendency of GLOF occurrences
becomes hard to verify. However, since the evaluation ofnatural hazards is a sensitive subject and difficult to predict, this issue warrants further discussion with additional
surveys.

5. Conclusion
In order to confirm the tendencies of GLOF occurrences in Bhutan, we investigated the most recent casesof GLOFs and minor outburst events in the past. Concerning the latest event in Bhutan, the Tshojo Glacier
flood in 2009 is mentioned as an outburst event fromsupraglacial lakes. The flood, which was initiated by lakewater leakage, and water splashing to the surface via an
en-/sub-glacial passage, points out a potentially dangerous hazard. The discrepancy in the estimated flood
volume between observations and remote sensing data
has been unsettling. There is a possibility that discharging of minor swollen water from one or more supraglaciallakes which could not be detected by water gauges,
continued in the days following the 29th of April. In any
case, attention to such outburst events from invisible
sources will be required in the future.
As for evaluating the frequency of GLOF incidents in
the Bhutan Himalayas, a total of 15 outburst cases wererecognized along with their years of the occurrence. A
total of 21 outburst cases, including some with publisheddata, were found from the Kuri Chu Tibetan branch,
Chamkhar Chu, Pho Chu, Mo Chu, Soe Chu and the
Tibetan side of the northwestern border. About half ofthem were generated at the foot of cliffs with hanging
glaciers. According to our investigation of various satellite photographs and imagery, 17 of these occurred
between the 19th century and the 1960s. On the other
hand, there were only four cases of outburst incidents inthe last 40 years. Hence, the frequency of outburst
occurrence does not seem to have increased. For accurateGlacial Lake Outburst Events in the Bhutan Himalayas

preparedness and attention to GLOF hazard mitigation,
field surveys and remote sensing research intended to list
minor events have to be broadened to include at least theother areas of the eastern Himalayas. This would make itpossible to discuss the conditions of outburst occurrences
and triggers with sufficient evidence.

Acknowledgements
The authors are indebted to all parties involved in the
project entitled “Study on Glacial Lake Outburst Floodsin the Bhutan Himalayas” financed under the Science andTechnology Research Partnership for Sustainable Development (SATREPS) program, and supported by theJapan International Cooperation Agency (JICA) andJapan Science and Technology Agency (JST). We express special gratitude for the satellite data and valuable
information provided by the project’s satellite researchteam. We are also grateful for the cooperation of the
Bhutanese members of the project in the Royal Bhutan
Government.
References
Ageta, Y. and S. Iwata (1999) Report of Japan–Bhutan Joint
Research 1998 on the Assessment of Glacier Lake Outburst
Flood (GLOF) in Bhutan. Institute for Hydrospheric-Atmospheric Sciences, Nagoya University, Nagoya.
Bart, J. (2008) Bhutan: A Trekker’s Guide, Cicerone Press,
Cumbria.
Benn, D.I., S. Wiseman and K.A. Hands (2001) Growth anddrainage of supraglacial lakes on debris-mantled Ngozumpa
Glacier, Khumbu Himal, Nepal. Journal of Glaciology, 47:
626-638.
Chen, C., T. Wang, Z. Zhang and Z. Liu (1999) Glacial lake outburst floods in upper Nainchu River basin, Tibet. Journal of
Cold Regions Engineering, 13: 199-212.
Chiba, T., S. Kaneta and Y. Suzuki (2008) Red Relief Image Map:
New Visualization Method for Three Dimensional Data. The
International Archives of the Photogrammetry, Remote Sensing
and Spatial Information Sciences, 37: 1071-1076.
Clague, J.J. and S.G. Evans (2000) A review of catastrophic drainage of moraine-dammed lakes in British Columbia. Quaternary
Science Reviews, 19: 1763-1783.
Dwivedi, S.R., M.D. Acharya and R. Simard (2000) The Tam
Pokhari Glacier Lake ourburst flood of 3 September 1998.
Journal of Nepal Geological Society, 22: 539-546.
Fujita, K., R. Suzuki, T. Nuimura and A. Sakai (2008) Performanceof ASTER and SRTM DEMs, and their potential for assessing
glacier lakes in the Lunana region, Bhutan Himalayas. Journalof Glaciology, 54: 220-228.
Fujiwara, K. and T. Gomi (1995) The hazards due to Glacier Lake
Outburst Flood in Himalaya, NEPAL: Study of the Tsho Rolpa
Glacier Lake. Research Bulletin of the Hokkaido University
Forests, 52, 208-245.
Fushimi, H., K. Ikegami, K. Higuchi and K. Shankar (1985) Nepal
case study; catastrophic floods. International Association of
Hydrological Sciences, 149: 125-130.
Gansser, A. (1983) Geology of the Bhutan Himalaya, Birkhauser
Verlag, Basel.
Geological Survey of Bhutan (1999) Glaciers and Glacier Lakes in
Bhutan, Thimphu.
Ghimire, M.K., S. Dwivedi and K.C. Subhrant (2005) Glacial
study in Madi watershed with special reference to GLOF of69

2003. Journal of Nepal Geological Society, 32: 48-48.
Ives, J.D., R.B. Shrestha and P.K. Mool (2010) Formation of Glacial Lakes in the Hindu Kush-Himalayas and GLOF Risk
Assessment, International Centre for Integrated Mountain
Development (ICIMOD), Kathmandu.
Karma, T. and K.B. Taman (1999) Preliminary Report of Tshokar
Tsho in the Head Waters of Chamkhar Chu, Bhutan. Geological
Survey of Bhutan, Thimphu.
Karma, T., Y. Ageta, N. Naito, S. Iwata and H. Yabuki (2003)
Glacier distribution in the Himalayas and glacier shrinkage from1963 to 1993 in the Bhutan Himalayas. Bulletin of GlaciologicalResearch, 20: 29.40.
Komori, J., D.R. Gurung, S. Iwata and H. Yabuki (2004) Variationand lake expansion of Chubda Glacier, Bhutan Himalayas, during the last 35 years. Bulletin of Glaciological Research, 21:
49-56.
Komori, J., S. Iwata, D.R. Gurung and H. Yabuki (2005) Glaciallake development and the record of outburst flood in the
North-central Bhutan and Kulha Kangri Massif, Eastern
Himalaya. Proceedings of International Symposium, Landslide
Hazard in Orogenic Zone from the Himalaya to Island Arc in
Asia, 119-125.
Mool, P.K., D. Wangda, S.R. Bajracharya, K. Kunzang, D.R.
Gurung and S.P. Joshi (2001) Inventory of Glaciers, Glacial
Lakes, and Glacial Lake Outburst Floods, Bhutan. ICIMOD,
Kathmandu.
Osti, R., S. Egashira, M. Miyake and T.N. Bhattarai (2010) Field
assessment of Tam Pokhari Glacial Lake Outburst Flood in
Khumbu Region, Nepal. Journal of Disaster Research, 5: 264273.
Richardson, S.D. and J.M. Reynolds (2000) An overview of glacial
hazards in the Himalayas. Quaternary International, 65/66:
31-47.
Shakti, P.C. (2009) Flash flood due to glacier lake outburst floodsin the mountainous region of Nepal: a case study of Kawache
Glacier Lake Outburst Flood. In: J. Feyen, K. Shannon and N.
Matthew, eds., Water and Urban Development Paradigm,
329-335.
Vuichard, D. and M. Zimmermann (1987) The 1985 Catastrophic
drainage of a moraine-dammed lake, Khumbu Himal, Nepal:
cause and consequences. Mountain Research and Development,
7: 91-110.
Watanabe, T. and D. Rothacher (1996) The 1994 Lugge Tsho
glacial lake outburst flood, Bhutan Himalaya. MountainResearch and Development, 16: 77-81.
Xu, D. and Q. Feng (1994) Dangerous glacier lakes and their
outburst features in the Tibetan Himalaya. Bulletin of GlacierResearch, 12: 1-8.
Yamada, T. and C.K. Sharma (1993) Glacier lakes and outburst
floods in the Nepal Himalaya. International Association of
Hydrological Sciences, 218: 319-330.
Yamanokuchi, T., T. Tadono, J. Komori and T. Koike (2011) Temporal monitoring of supraglacial lakes on Tshojo Glacier at
Bhutan, Abstract on International Geoscience and Remote
Sensing Symposium 2011.

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J. KOMORI et al.
Jiro KOMORIJiro KOMORI is a JICA expert on technical/
research cooperation in Bhutan, and holds anappointment as a Contract Assistant Professor at
the Graduate School of Environmental Studies,
Nagoya University. As a JICA expert, he has
been dispatched to the newly established
Division of Glaciology at the Department of Geology and Mines, Royal
Government of Bhutan since 2009. Originally he worked for four years as
an engineer at a geological consulting company and subsequently for four
years at Nihon University as a laboratory assistant until 2000. He obtained
his PhD in paleoenvironmental studies from the Graduate School of Tokyo
Metropolitan University in 2005. As a graduate student, he also started to
study subjects such as disaster prevention related to recent environmental
change. His first field survey of glaciers and glacial lakes was in the
Bhutan Himalayas in 2002. This brought an opportunity for precious
experience and many encounters in Bhutan to not only himself but also his
family. He currently has a keen interest and is seeking ways to disseminate
the results of this research and educate the younger generation regarding
the issues of environmental change rather than interest in the naturalsciences.

Toru KOIKE
Toru KOIKE is a Deputy General Manager of theEnvironmental & Disaster Management Department at Earth System Science Co., Ltd. He has
been working in the field of disaster management,
including geological and river engineering under
Official Development Assistance funding fromthe Japanese government. During 2000-2002, he lived in Bhutan andworked for the Department of Geology & Mines. Currently he is working
in disaster related projects in Thailand, Vietnam, Bhutan, Bolivia andCaribbean countries.

Tsutomu YAMANOKUCHI
Tsutomu YAMANOKUCHI joined the Remote
Sensing Technology Center of Japan (RESTEC)
in 1995. He is currently in charge of cryosphericapplications using ALOS data mainly at mountainglaciers and in Antarctica. He also dedicatesefforts to capacity building of satellite datautilization through hands-on training to users in developing countries. He
received his B.S. degree in Astrophysics from Nagoya University, Aichi
Pref., Japan in 1993, M.S. degree in Oceanography from Kyushu
University, Fukuoka Pref., Japan in 1995, and a Ph.D. in Science from the
Graduate University for Advanced Studies.

Phuntsho TSHERING
Phuntsho TSHERING is a geologist working in the
Department of Geology and Mines, Ministry of
Economic Affairs, Royal Government of Bhutan.
He did his undergraduate work in the fields ofMathematics, Physics and Geology at the Post
Graduate College of Science, Osmania University, India. One year after joining the department in 2008, he started
working in the Glaciology Division and since then, he has been an active
counterpart for a collaborative research project involving his department,
JICA and JST. Working together with the JICA experts, he has been
actively involved in implementing field activities along the northern
glaciated frontiers of Bhutan in 2009, 2010 and 2011. Having been
involved in such activities, he has a keen interest in specializing in thefields of environmental sciences and global climate change and its
associated risks.

(Received 26 December 2011, Accepted 14 February 2012)