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Glacier Retreat, Lakes Development
and Associated Natural Hazards
in Cordilera Blanca, Peru
Adam Emmer, Vít Vilímek, Jan Klimeš and Alejo Cochachin
Abstract Cordillera Blanca is the heaviest glacierized tropical range in the world.
Due to the global climate change, most of glaciers are retreating and thinning.
Glacier retreat leads to the formation and development of all types of potentially
hazardous glacial lakes (bedrock-dammed, moraine-dammed, and ice-dammed).
Potential hazardousness of glacial lakes is strongly interconnected with dynamic
slope movements: (1) sudden release of water from glacial lakes (also known as
glacial lake outburst floods—GLOF) is mainly caused by dynamic slope move-
ment into the lake (about 80 % in the Cordillera Blanca); (2) released water may
easily transform into debris-flow or mud-flow, thanks to its high erosion and
transport potential. Based on field study and remotely sensed images, this
contribution documents glacier retreat in the Cordillera Blanca with regards to
formation and development of new potentially hazardous glacial lakes, which
evolve mainly in elevations of about 4,600–5,000 m a.s.l. We introduce and
describe three hazardous events associated with glacier retreat in the last decade:
(a) sudden release of water from moraine-dammed Lake Palcacocha in 2003;
(b) sudden release of water from bedrock-dammed lake No. 513 in 2010; and
(c) sudden release of water from bedrock-dammed Lake Artizon Alto and
A. Emmer (&)V. Vilímek
Department of Physical Geography and Geoecology, Faculty of Science,
Charles University in Prague, Albertov 6, 128 43 Prague 2, Czech Republic
e-mail: aemmer@seznam.cz
V. Vilímek
e-mail: vit.vilimek@natur.cuni.cz
J. Klimeš
Institute of Rock Structure and Mechanics, Academy of Sciences of the Czech Republic,
V Holešovic
ˇkách 41, 182 09 Prague 8, Czech Republic
e-mail: jklimes@centrum.cz
A. Cochachin
Unidad de Glaciologia y Recursos Hidricos, Authoridad National de Agua Av.
Confraternidad Internacional 167, Huarás, Peru
e-mail: acochachin@hotmail.com
W. Shan et al. (eds.), Landslides in Cold Regions in the Context of Climate Change,
Environmental Science and Engineering, DOI: 10.1007/978-3-319-00867-7_17,
Springer International Publishing Switzerland 2014
231
subsequent moraine dam failure of downstream situated Lake Artizon Bajo in
2012. The first and third events were caused by landslides of lateral moraines
(which are often non-
consolidated and nearly vertical) into the lakes. The second event was caused by
ice- and rockfall into the lake. These events illustrate that various natural hazards
(dynamic slope movements, floods) associated with glacier retreat in the Cordillera
Blanca are closely linked and represent actual threats to urbanization and safety of
lives and property.
Keywords Natural hazards Glacier retreat Dynamic slope movements
GLOFs The Cordillera Blanca
1 Introduction
Impact of climate change to glacier retreat and thinning (downwasting) and
associated natural hazards in high mountain areas has been described by O’Connor
and Costa (1993) and more recently, by Clague et al. (2012). Glacier retreat is
closely tied with various types of natural hazards which have potential to cause
significant damages. These include direct and indirect dynamic slope movements
(Richardson and Reynolds 2000a), catastrophic floods following sudden water
release from any type of high mountain lake (Costa and Schuster 1988), earth-
quakes following intense ice loss (deglaciation-induced earthquakes) (Harrison
et al. 2006), and also, changes in runoff regime followed by droughts (Mark 2002).
These apparently disparate natural hazards are in fact naturally linked. Based on
remotely sensed photographs and field study conducted in 2010, 2011 and 2012,
this contribution brings three examples of ties (links) among glacier retreat,
selected glacial lake development (Fig. 1), various types of dynamic slope
movements and outburst floods in the Cordillera Blanca mountain range (Peru).
Richardson and Reynolds (2000a) distinguishes between direct and indirect
dynamic slope movements associated with deglaciation. Direct dynamic slope
movements associated with deglaciation are snow/ice avalanches, while indirect
are mass re-organizing paraglacial processes affecting steep sided valleys—e.g.
rock avalanches and landslides. This phenomenon of indirect dynamic slope
movements associated with deglaciation is also called ‘‘landslide response to post-
Little Ice Age glacier retreat and thinning’’ (Holm et al. 2004). Together, these two
groups of dynamic slope movements represent the most frequent trigger of sudden
and often catastrophic water release from glacial lakes in the Cordillera Blanca—
80 % overall of which 45 % are direct and 35 % indirect dynamic slope move-
ments into the lake. The remaining 20 % of sudden water release from glacial
lakes in the Cordillera Blanca are due to earthquakes and flood waves from lakes
situated upstream (Emmer and Cochachin 2013). A sudden water release from any
type of glacial lake irrespective of its cause is called a ‘‘Glacial lake outburst
232 A. Emmer et al.
flood’’ (GLOF). A GLOF may result from failure or overflow of a glacial lake dam
and, thanks to its high erosion and transport potential, may easily transform into
flow movement (e.g. debris-flow or mud-flow). These events claimed thousands of
lives during the 20th century, and caused significant damage in the Cordillera
Blanca. The most catastrophic was the moraine-dam failure of lake Palcacocha in
1941 and the moraine-dam failure of lake Jancarurish in 1950 (Zapata 2002).
2 Study Area: The Cordillera Blanca
The Cordillera Blanca is located in the northcentral Andes, in the Ancash region of
Peru (8.5–10S; 77–78W). This mountain range is part of the Cordillera
Occidental (Western Cordillera). The Cordillera Blanca is the highest Peruvian
mountain range with sixteen peaks over 6 000 m a.s.l. and also the most heavily
glacierized tropical range in the world, with present glacier extent of about
600 km
2
(Georges 2004). This figure represent approximately one fourth of
worldwide extent of tropical glaciers (Ames and Francou 1995). The western part
of the Cordilllera Blanca is drained by Rio Santa into the Pacific Ocean, while the
eastern part is drained by Rio Marañon and then by the Amazon River into the
Atlantic Ocean (Fig. 1). The geological structure is very complicated and differs
from south to north as well as from east to west. The upper parts of the Cordillera
Blanca are underlain by granitic intrusions, but there are also parts which are
Fig. 1 The Cordillera Blanca and the location of lakes mentioned in this paper (base map USGS)
Glacier Retreat, Lakes Development and Associated Natural Hazards 233
underlain by extrusive vulcanic rocks such as andesitic rocks and tuffs or
sedimentary rocks such as sandstones and shales (Wilson et al. 1995). The
Cordillera Blanca is an active seismic region, where large earthquakes occur (e.g.
1970 earthquake with M7.7), cause significant damages and also initiate various
types of natural hazards such as dynamic slope movements or GLOFs (Lliboutry
et al. 1977). The main fault zone extends approximately 210 km through the
western slopes of this range.
2.1 Glacier Retreat
The Cordillera Blanca had been glacierized several times in geologic history and
the glacier extent was much more extensive during the late Pleistocene and
Holocene (Mark 2002; Vilímek 2002). Clear evidence of past glacier extent such
as massive moraines, U-shaped valleys and striations can still be found in reliefs,
kilometers away from the present position of glaciers. The last significant glacier
advance happened during the so called ‘‘Little Ice Age’’—a relatively cold period,
which culminated (according to lichenometric dating and ice-core data from
Huascarán glacier) from 1590 to 1720 and less extensively from 1780 to 1880
(Thompson et al. 2000; Solomina et al. 2007). Since the end of the Little Ice Age,
glaciers started to retreat and new glacial lakes began to form and develop.
Moraines that formed during the Little Ice Age mark the maximal glacier extent
during this period, but there is no appropriate evidence for the subsequent glacier
retreat during the 19th Century. Glaciers of the Cordillera Blanca have been
inventoried several times in the 20th Century and the trend of retreat and thinning
is obvious. Georges (2004) reconstructed the extent of glaciers in the 1930s to
800–850 km
2
, based on the first aerial photographs of this region. According to
remotely sensed photographs of this area in the 1970s, the extent of glaciers
decreased in 40 years to 723 km
2
(Ames and Francou 1995). The latest investi-
gation demonstrated that the extent of glaciers was about 600 km
2
at the beginning
of the 21st Century (Georges 2004). These numbers show that glacier extent has
decreased by about one fourth since the 1930s. The total volume of glaciers can
also be assumed to have decreased in this period, due to downwasting. This intense
glacier retreat and thinning is visible on all glaciers within the Cordillera Blanca;
nevertheless, there are some differences in the rates of glacier retreat. Areal and
volumetric glacier retreat is mostly controlled by various combinations of the
following factors:
1. Meteorological regime—solar radiation—energy for glacier thawing is mostly
gained from solar radiation, thus a very important characteristic is the total
number of hours of sunshine in a year and aspect of slopes and its exposition
(see below) (Oerlemans and Knap 1998; Mark 2002)
•temperatures and precipitation (e.g. Huggel et al. 2004)—every part (valley)
of the Cordillera Blanca has a specific meteorological regime, but in general,
234 A. Emmer et al.
sites with higher temperatures and/or lower precipitation have greater rates of
glacier retreat
2. Topographic setting—aspect—aspect is generally considered as one of the most
important non-climatic characteristics influencing rate of glacier retreat,
because it is closely connected with hours of solar radiation. Glaciers with an
eastern aspect have the highest rate of glacier retreat within the Cordillera
Blanca, while glaciers with southwestern aspect have lower rates of glacier
retreat (Mark 2002)
•exposure—exposition is a second topographical characteristic, which con-
trols rate of solar radiation. That is, sites which are often shaded by sur-
rounding terrain receive less solar radiation than exposed sites.
3. Glacier characteristics—area (volume) of glacier—Larger glaciers have a
greater volume of ice and lower initial rates of retreat and thinning; larger ice
bodies are able to resist for a long time (Kaser 1995)
•debris coverage—the role of debris cover on glacier retreat is not uniform.
On one handglacier tongues covered by a thick debris layer are able to resist
the direct impact of solar radiation and thus may persist for a longer time in
lower altitudes (in the form of buried ice). On the other hand glacier tongues
covered by a thin debris layer thin easily, due to heat exchange between the
ice body and dark debris with a higher heat capacity and lower albedo
(Richardson and Reynolds 2000b).
The number of glacial lakes in the Cordillera Blanca during the 20th Century
increased with a decrease in the extent of the glacierized area (Table 1). The first
inventory of lakes was presented by Concha (1951) who showed that there were
230 lakes of significant size at the beginning of the 1950s, of which most of the
glacial lakes in altitudes between 4,250 and 4,600 m a.s.l. Morales et al. (1979)
updated the overall number of lakes of significant size to 267. Portocarrero (1995)
summarised 899 lakes in the Cordillera Blanca and now there are more than one
thousand of lakes overall (see Table 1), and new lakes form and develop in the
altitudes between 4,600 and 5,000 m a.s.l.
Table 1 Decreasing extent of glacierized area and increasing number of lakes since 1930 within
the Cordillera Blanca
Years Glacier extent (km
2
) Number of lakes References
1930 800–850 – Georges (2004)
1951 – 230 (lakes of significant size) Concha (1951)
1970 723 267 (lakes of significant size) Ames and Francou (1995);
Morales et al. (1979)
1995 – 899 (overall) Portocarrero (1995)
2000 600 – Georges (2004)
2012 \600 [1,000 (overall) This study
Glacier Retreat, Lakes Development and Associated Natural Hazards 235
2.2 Typology of Glacial Lakes
A glacial lake is a lake, whose basin was excavated by glacial erosion, dammed by
a glacier body or moraine or some combination of these. A number of typologies
of (glacial) lakes for different purposes and regions have been created e.g. by
Hutchinson (1957), or later by Kalff (2002) or Jansky
´et al. (2006). Typology of
lakes within the Cordillera Blanca with regard to its potential hazardousness was
first presented by Concha (1951). One of the most common typologies is one that
divides glacial lakes according to the material which forms the lake dam. This
typology generally distinguishes between:
1. bedrock-dammed lakes;
2. moraine-dammed lakes; and
3. ice-dammed lakes.
The first and second types easily reach a significant volume of accumulated
water (from 10
6
to 10
7
m
3
) within the Cordillera Blanca, while the third type does
not.
Bedrock-dammed lakes form in depressions excavated by glacial erosion after
its retreat. The dam of the lake is composed of solid rocks, and thus is considered
to be stable (Huggel et al. 2004). Therefore, dam breach is not a possible scenario
for sudden water release, unlike the dam overflow. This type of lake is very
common within the Cordillera Blanca, but they are often insignificant in size. Of
course, there are some which exceed a volume of 10
6
m
3
(e.g. lake No. 513, lake
Auquiscocha or lake Churup), but most of them do not.
Concha (1951) distinguished between bedrock-dammed lakes with direct contact
with a glacier and without contact with a glacier, because direct contact with a glacier
and the possibility of it calving into the lake and producing displacement waves is a
very important characteristic in the potential hazardousness of the selected lake. New
bedrock-dammed lakes evolve in present days, some of them evolve in hanging
valleys mostly at altitudes ranging between 4,600 and 5,000 m a.s.l. An example of a
new, rapidly growing bedrock-dammed lake is an unnamed lake situated beneath the
eastern slopes of Chopicalqui massif (6,354 m a.s.l.). This lake enlarged its area
between 2003 (Fig. 2a) and 2011 (Fig. 2b) more than two times. The volume of
accumulated water, which is available for sudden water release, is also increasing
rapidly. The maximum length of the lake was more than 500 m in 2011 and there is a
great potential for further growth following glacier retreat.
Moraine-dammed lakes are most frequently formed behind moraines after
glacier retreat. This type represents the largest lake in the Cordillera Blanca. The
volume of accumulated water may exceed 10
7
m
3
. Some examples are Lakes
Jancarurish (12,322 910
6
m
3
; Fig. 3a); Rajucolta (17,546 910
6
m
3
; Fig. 3b),
and Placacocha (17,325 910
6
m
3
; Fig. 3c), which are all dammed by massive
moraines formed during the Little Ice Age at elevations between 4,250 and
4,600 m a.s.l. All these examples of very large contemporary moraine-dammed
lakes within the Cordillera Blanca had produced GLOFs in history (Rajucolta in
236 A. Emmer et al.
1883; Palcacocha in 1941 and 2003; and Jancarurish in 1950) (Zapata 2002). The
height of LIA moraine dams may exceed one hundred meters and their slopes are
frequently very steep and unstable. Richardson and Reynolds (2000a) showed that
lakes formed behind LIA moraines are potentially dangerous because they are
dammed by unconsolidated and poorly sorted material which enhances dam fail-
ures, and at the same time, they are often in direct contact with the glaciers
(icefalls into the lake represent the most frequent trigger for outburst floods).
Clague and Evans (2000) showed that moraine-dammed lakes most commonly fail
at the beginning of glacier retreat. The Cordillera Blanca is an example of this
scenario.
Concha (1951) divided moraine-dammed lakes of the Cordillera Blanca into
more categories. The first distinction is between moraine dams with steep slopes
and moraine dams with gentle slopes, but no critical value is given, thus the
Fig. 2 Unnamed growing bedrock-dammed lake beneath the eastern slopes of Chopicalqui
massif. Part awas taken in 2003, while part bwas taken in 2011. Clear evidence for a small
outburst flood after overflowing the dam following glacier calving or landslide of lateral moraine
into the lake is visible in part b(Source Google Earth Digital Globe 2013)
Glacier Retreat, Lakes Development and Associated Natural Hazards 237
classification is quite subjective. The second distinction, in the case of bedrock-
dammed lakes, is between moraine-dammed lakes with direct contact with glaciers
and without direct contact with glaciers. These two characteristics in a simplified
way reflect potential hazardousness of moraine-dammed lakes. That is, the slope of
a moraine dam reflects its potential to failure and contact with glaciers reflects the
possibility of icefall into the lake to trigger its failure.
Ice-dammed lakes are generally considered as one of the less stable types of
lakes (Korup and Tweed 2007). Various subtypes of ice-dammed lakes were
defined by Costa and Schuster (1988) according to the position of the lake in
relation to the glacier. Only one subtype of ice-dammed lakes is represented in
Cordillera Blanca—supraglacial lakes. This subtype of ice-dammed lakes is a
product of surface glacier melting and evolves directly on the glacier tongue body.
Merging of small lakes may produce a large one, but obvious instability of ice
dams limit the possibility of development of supraglacial lakes of significant size.
If glacier tongue is surrounded by moraines, merging of supraglacial lakes usually
foregoes to formation of moraine-dammed lake.
There is no ice-dammed lake of significant size in the Cordillera Blanca at the
moment, because these most frequently appear after damming of a lateral valley by
an advancing glacier in the main valley, or after damming of the main valley by an
advancing glacier from a lateral valley (Costa and Schuster 1988); but there is a
Fig. 3 Examples of failed moraine dams within the Cordillera Blanca. Part ashows the moraine
dam of lake Jancarurish in de Los Cedros valley (failed in 1950), part bthe moraine dam of lake
Rajucolta in the Rajucolta valley (failed in 1883) and part cthe moraine dam of lake Palcacocha
in the Cojup valley (failed in 1941)
238 A. Emmer et al.
high number of small supraglacial lakes that developed on glacier tongues with
gentle slopes. Maximal perimeter of these lakes is in the order of tens of meters
and the estimated volume of accumulated water reaches 10
4
m
3
. Example of a site
with a large number of ice-dammed lakes (subtype supraglacial lakes) is the
tongue of Kogan glacier (Fig. 4a), beneath the northern slopes of Quitaraju massif
(6,036 m a.s.l.). Development of these lakes indicates intense thinning of the
Kogan glacier. The glacier tongue is not surrounded by a terminal moraine and
thus the formation of a moraine-dammed lake by merging of small supraglacial
lakes is not a possible scenario, in contrast to the tongue of Schneider glacier
(Fig. 4b) beneath the eastern slopes of Huascarán Sur massif (6,768 m a.s.l.). The
debris-covered tongue of Schneider glacier is surrounded by moraines, so there is a
potential for future development of a significant moraine-dammed lake by merging
of small supraglacial lakes.
3 Case Studies
Three examples illustrate the interconnections between glacier retreat, dynamic
slope movements and potential hazards posed by developing glacial lakes. These
events occurred in the last decade and caused material damages in affected valleys.
3.1 Lake Palcacocha 2003 Event
Lake Palcacocha is situated at the upper part of Cojup valley, which is oriented in
the NE-SW direction under the Nevado Palcaraju (6,274 m a.s.l.) and Nevado
Pucaranra (6,165 m a.s.l.). Terminal and lateral moraines were formed during the
little ice age glacier advance, and with glacier retreat after this period a moraine-
dammed lake formed and continued to expand. On 13rd December 1941, the
moraine dam failed, probably after an icefall into the lake which produced a
displacement wave, and the wave eroded the outflow of the dam (Oppenheim
1946). The volume of water released was estimated to be between 8 910
6
m
3
(Evans and Clague 1994) to 10
7
m
3
(Vilímek et al. 2005). The resultant glacial
lake outburst flood transformed into debris flow, travelled down the valley, and
invaded the city of Huaráz, where it claimed about 6,000 lives and destroyed one
third of the whole city (Lliboutry et al. 1977). Currently, Lake Palcacocha is
dammed by a basal moraine with two artificial dams (Fig. 5a) and its volume
reached 17,325 910
6
m
3
during the 20th Century due to continuing glacier retreat
(Vilímek et al. 2005).
A small GLOF was produced from Palcacocha Lake during March 19th 2003
by a planar landslide which crashed into the lake. The probable triggering factor
was the over-saturation of the moraine material by precipitation. The 2003 land-
slide occurred in the inner part of the left lateral moraine adjacent to the glacial
Glacier Retreat, Lakes Development and Associated Natural Hazards 239
tongue—in the location where prominent drop-offs of the moraine slope were
identified on the 1970 aerial pictures (Vilímek et al. 2005). These features were
also seen during fieldwork in 2003 (Zapata et al. 2003), and we assume that these
might have played an important role in water infiltration and in the evolution of the
planar sliding plane of the landslide. The landslide hits partly the glacial tongue.
The volume of the slope movement was estimated to be about 50,000–75,000 m
3
.
A displacement wave which was created in the lake was at least 8 m high. The
wave reached the frontal dam of Palcacocha Lake and after overtopping, it created
a small GLOF in Cojup stream and Quilcay River. Fortunately large damages were
avoided, nevertheless the water treatment plant for Huarás, capital city of Ancash
Fig. 4 Tongues of Kogan glacier in 2012 (part a) and Schneider glacier in 2003 (part b) with
tens of small supra-glacial lakes. The debris-covered tongue of Schneider glacier is surrounded by
moraines and thus there is a potential for future formation and development of a moraine-
dammed lake (Source Google Earth Digital Globe 2013)
240 A. Emmer et al.
department, was blocked by sediment-laden currents and also an aritificial dam of
the lake was partly damaged (Fig. 5b). The landslide left no significant accumu-
lation on the lakeshore. A secondary debris flow originated from the highly sat-
urated material from the upper part of the moraine slope and produced a small
accumulation cone. Field mapping around the glacial lake showed that the right
lateral moraine on the opposite side of the lake shows signs of rather fresh but
smaller planar landslides.
The most active parts of the entire inner slopes are those adjacent to the glacial
tongue.The adjacent slopes became distabilized as the glacier retreated (Vilímek
et al. 2005). This condition finally led to the landslides. Slopes without glacial
support are turning towards a more stable profile based on the mechanical prop-
erties of the moraine material. This led to a gradual decrease in the inner moraine
slopes and to the accumulation of moraine material in the lake. Evans and Clague
(1994) mentioned with respect to high mountain slopes that the slope instability
could persist after glacier retreat for perhaps hundreds of years. Comparison of
remotely sensed data showed that the main phase of the glacial tongue retreat did
not happend since 1970 (Vilímek et al. 2005). As a result of these processes, the
maximal width of the lake is in the part adjacent to the glacial tongue.
The precise role of landslides in glacial retreat is not clear, but field investi-
gations in 2004, after the March 2003 landslide, proved that part of the glacial
tongue was destroyed and broken to small ice blocks by the landslide. The impact
of these landslides might have contributed to glacier’s disintegration in the past
and therefore to its more rapid thawing. Our recent research in this area is focused
Fig. 5 View on lake Palcacocha with two artificial dams (highlighted by the orange line); steep
nearly vertical lateral moraines are visible on both sides surrounding the lake. The detail picture
(Part b) was taken after the 2003 event and captures the damaged artificial dam
Glacier Retreat, Lakes Development and Associated Natural Hazards 241
on calculation of slope stability in moraines and on geophysical profiling, because
other moraine blocks are distinguishably separated into left lateral moraine. The
precise detachment zones have to be fixed to calculate their volumes.
3.2 Lake No. 513 2010 Event
The Lake No. 513 is a bedrock-dammed lake which is the largest of a group of
three lakes situated in the central part of the Cordillera Blanca beneath the western
slopes under Mt. Hualcán (6,122 m a.s.l.) with a water level of 4,437 m a.s.l.
These slopes are formed by steep rock-walls fully covered by glaciers. This area
consists of intrusive rocks formed from sharp modelled peaks and crests. Litho-
logically, they are composed of coarse-grained granodiorites and tonalites. Several
hanging ice blocks were identified during our field inspection (2010 and 2011) as
well as from satellite images. Ice and rock falls originating from similar settings
represents devastating disasters in the Cordillera Blanca many times in the past
(e.g. Zapata 2002; Klimeš et al. 2009). Frontal parts of the glaciers in the lake
surrounding terminate in the altitude between 4,600 and 4,800 m a.s.l. depending
on local morphology. However, the longest tongue reached the lake with an ice-
fall crossing a 150 m high rocky step. Lake No. 513 is classified as a bedrock-
dammed lake, before the artificial lowering of the water level, a combined bedrock
and moraine dam was formed here after the glacier retreat. Now the moraine crest
does not hold any water, which is entirely contained behind solid rocks.
During the 1970 earthquake in Ancash Peru, an ice avalanche from the eastern
wall of the Hualcán mountain crashed into Lake Librón in the Huichajanca valley,
in the Marañón River basin (Zapata 2002). Another event from Lake No. 513
happened in 1991 and was described by Carey et al. (2012). In April 11th 2010 a
large block of glacier together with rocks, crashed from the southwestern part of
Mt. Hualcán slope (Fig. 6a) into Lake No. 513 and part of the lake water over-
flowed the dam and created a GLOF in the Chucchún River valley, a right tributary
to the Santa River. During this event some houses, roads, bridges and an important
water treatment facility were destroyed, fortunately no fatality was recorded. The
rather low extent of damage is due to the fact that the valley is not densely
populated and some villages were out of reach of the debris flow. The debris flow
went into the city of Carhuaz as well, but again only limited damages occurred.
However, from geomorphologic point of view, this event was rather strong,
because a large amount of material was transported down the valley. Lateral
erosion was documented inside the valley (Fig. 6b) as well as large blocks
accumulated at several places in the valley where stream power decreased
(Fig. 6c). However, for the case of larger rock- or ice-fall into the lake, a much
more serious disaster is likely to occur within the area in the near future.
242 A. Emmer et al.
3.3 Lakes Artizon Alto and Artizon Bajo 2012 Event
Lakes Artizon Alto and Artizon Bajo are situated in a head of Artizon valley,
which is a left-sided tributary of the Santa Cruz valley in northern part of the
Cordillera Blanca. This is a part of the Rio Santa basin which drains into the
Pacific Ocean. The Artizon valley is oriented to the North and is surrounded by
three conspicuous peaks—Nevado Artesonraju (6,035 m a.s.l.) from the south-
west, Nevado Parón (5,600 m a.s.l.) from the South, and Nevado Millisraju
(5,500 m a.s.l.) from the East. The event which occurred on 8th February 2012 is
one of the most recent GLOF events in the Cordillera Blanca, and it affected four
lakes and two valleys. The sequence of important events in the formation and
development of the Artizon lakes is reinterpreted below:
1. Glacier retreat was followed by formation and development (deepening) of the
Artizon lakes; moraine-dammed lake Artizon Bajo is about 300 m long and
140 m wide with volume of accumulated water, 333,000 m
3
(Huaman 2001);
Fig. 6 Part ashows Hualcán massif above Lake No. 513; the source area of 2010 ice and rock
avalanche is highlighted by orange circle. Part bshows a part of Chucchún valley with
dominance of erosional processes and part cshows a part of valley with dominance of
accumulation processes
Glacier Retreat, Lakes Development and Associated Natural Hazards 243
bedrock dammed Lake Artizon Alto is about 750 m long and 200 m wide,
with a significant rock peninsula which divides the lake into two sub-basins
(Fig. 7a)
2. Continuing retreat and thinning of the glacier tongue above the Lake Artizon
Alto to the altitude of about 4,800 m a.s.l.
3. Steep lateral moraines are no longer supported by the glacier body and thus
they are predisposed to slope movements; in 2001 it was recommended to
lower the water level of Lake Artizon Bajo due to the possibility of landslides
into Lake Artizon Alto (Huaman 2001)
4. On 8th February 2012, a landslide of the left lateral moraine (approximate
volume in order of 3–8 910
5
m
3
) into Lake Artizon Alto occurred (Fig. 7b),
generating a displacement wave
•the direct trigger of the landslide is not exactly known, but a probable
trigger is precipitation (according to SENAHMI precipitation measurements
in Yungay and Pamabamba, both about 25 km far from Arteson valley),
there was intense precipitation during the last few days before this event)
•another common trigger of dynamic slope movements in the Cordillera
Blanca is earthquake, but according to the USGS earthquake archive, there
was no earthquake on 8th February 2012 in the northern part of the Cordillera
Blanca
•we suggest that a moraine landslide may have occurred due to precipitation
in combination with degradation caused by ice core melting.
5. The displacement wave following the landslide entered into the lake and
overflowed the bedrock dam of Lake Artizon Alto and reached Lake Artizon
Bajo.
6. The moraine dam of Lake Artizon Bajo was overflowed and a ‘‘positive
feedback’’ effect caused a breach and moraine dam failure; the flood wave
from Lake Artizon Alto increased its overall volume of about 2 910
5
m
3
water from Lake Artizon Bajo.
7. Escaped water transported a large amount of moraine material and signifi-
cantly affected the Artizon valley (erosion in the upper part of the valley and
deposition in the form of an alluvial fan in the mouth of the valley into the
Santa Cruz valley. The central part of the Santa Cruz valley was also affected,
mostly by accumulation processes, sand bar formation, and partial transfer of
stream channel (Fig. 7c).
8. The released volume of water reached and then was partly absorbed by
landslide-dammed lake Jatuncocha in the Santa Cruz valley; also material
influx into the lake was significant, the lake was shortened by about 80 m and
the lake area also decreased.
9. There was also minor damage to the artificial dam of Lake Jatuncocha due to
increased flow rate.
244 A. Emmer et al.
Fig. 7 Lakes Artizon Alto and Artizon Bajo in 2003 before (part a) and in 2012 after (part b) the
2012 GLOF event. The orange highlighted line represents the extent of the glacier. Please note
the significant glacier retreat. The yellow color in part brepresents the accumulation of landslide
of a lateral moraine, which entered the lake Artizon Alto on 8th February 2012. Part c
demonstrates the dominant processes in the valleys Artizon and Santa Cruz after water release
(red color—parts of the valley with erosion processes dominant; green color—parts of the valley
with accumulation processes dominant) (Source Google Earth Digital Globe 2013)
Glacier Retreat, Lakes Development and Associated Natural Hazards 245
10. Increased flow rate from Lake Jatuncocha with no sediment load eroded part
of Santa Cruz valley before reaching another landslide-dammed lake (Lake
Ichiccocha).
11. The rest of the flood wave was absorbed by Lake Ichiccocha.
In the affected valleys (the Artizon and Santa Cruz), we may generally dis-
tinguish between areas where erosion processes are prevalent and areas where
accumulation processes are prevalent. Erosion processes are prevalent on the
steeper parts of the valley, while accumulation processes are prevalent on the
flatter parts (Fig. 7c), except for a short flat part of the Santa Cruz valley beneath
the Lake Jatuncocha which was eroded by increased flow rate from this lake,
because all transported material was retained in the Jatuncocha Lake basin. The
stream banks in the steeper upper part of Artizon valley are more prone to slope
movements after the incision of the stream channel (undercutting the slopes), thus
there is a possibility of future slope movements and formation of a landslide-
dammed lake. An alluvial fan that was originally 300 m wide on the flatter part of
the Artizon valley has been extended to 500 m wide by transported material. The
position of the stream channel in the Santa Cruz valley has been changed by the
accumulation of sediment bars. This example shows how a local landslide into
the lake may subsequently affect valleys and lakes, which are kilometers away.
4 GLOFs: A Manageable Hazard??
The region of the Cordillera Blanca is relatively densely populated, so there is
urgent need to manage various natural hazards including GLOFs following sudden
release of water from any type of glacial lake. As shown above, occurence of
GLOF is a highly complex question which is strongly linked with other types of
natural hazards, mainly with dynamic slope movements or large earthquakes.
These hazards are difficult to quantify or to predict precisely in time, thus it is not
possible to completely prevent hazards associated with sudden release of water
from glacial lakes. Richardson and Reynolds (2000a) listed three phases of glacial
hazard management: the first phase is identification of a potential hazard, followed
by hazard assessment (second phase), and ideally, the third phase is hazard mit-
igation. Thanks to ongoing formation and development of all types of glacial lakes
in the Cordillera Blanca, it is important to reassess their potential hazards thor-
oughly. Potential hazard identification and reliable assessment are crucial steps in
risk estimation and effective management (Fig. 8).
246 A. Emmer et al.
4.1 Hazard Assessment
New potentially dangerous lakes are forming and developing (Klimeš 2012), and
existing lakes are rapidly changing their characteristics. It is highly important to
realize that potential hazardousness of glacial lakes is changing significantly
during short time periods, because high mountain environment is one of the most
dynamic natural environments worldwide. The previous examples of Lake Palc-
acocha and Lake No. 513 showed that GLOFs may occur even from a lake on
whose dam has been remediated, and which was considered as safe. Lake Palc-
acocha changed from a ‘‘safe lake’’ to one producing a GLOF in 30 years between
the 19700s and 2003 (Vilímek et al. 2005). During this period, the glacier retreated
about 1,000 m. This intense deglaciation led to rapid increase of water volume
accumulated in the lake. Also, lateral moraines with steep slopes were uncovered
and thus ready for landslide into the lake (2003 event). These are remarkable
changes, and also the reason why the results of hazard assessment should be
reevaluated after a certain period of time.
There are two phases of GLOF hazard assessment. The first phase aims at
estimating the possibility of sudden water release from any given glacial lake,
while the second phase aims at modelling the flood wave downstream, determining
Fig. 8 Schematic procedure for GLOF risk management [According to: Huggel et al. (2004);
Hegglin and Huggel (2008); Richardson (2010), and Shrestha (2010)]
Glacier Retreat, Lakes Development and Associated Natural Hazards 247
the endangered areas, estimating the probability of debris-flow occurrence and the
probable maximal travel distance (Huggel et al. 2004). There are a number of
methods for GLOF hazard assessment, but these events in Cordillera Blanca differ
in some ways from other world regions. These differences consist in share and
representation of causes of sudden water release and also in high number of
remedial work applied on dams in the Cordillera Blanca (see Sect. 4.2 Hazard
mitigation). This is necessary to be accounted for in precise hazard assessment for
glacial lakes within the Cordillera Blanca (Emmer and Vilímek, 2013).
4.2 Hazard Mitigation
Lakes of the Cordillera Blanca are famous for the high number of remedial pro-
jects (Carey 2005), which have been implemented since the 1940s. There are about
forty glacial lakes with dams that have been remediated (Reynolds 2003). Three
different types of remedial works were most commonly applied on glacial lakes
within this region:
1. Open cut—Open cut is carried out by countersinking the outlet of lakes which
do not have a solid rock dam (moraine-dammed lakes). The countersunken
outlet is usually combined with artificial dam construction, but sometimes is not
(e.g. Lake Arhueycocha). Open cut cannot be applied to bedrock-dammed
lakes, therefore in this case tunnels are used (see below) to lower the water
level permanently. Open cut allows the water level to be decreased and thus
reduces the volume of accumulated water.
2. Artificial dam—The main purpose of an artificial dam is to increase dam
freeboard and thus enable the dam to be resistant against displacement waves
generated by dynamic slope movements into the lake. Most significant glacial
lakes within the Cordillera Blanca were remediated by a combination of a
concrete outflow and an artificial dam [e.g. Lake Llaca (Fig. 9a), or Lake
Rajucolta (Fig. 9b)]
3. Tunnel—Tunnels are used to decrease and limit the water level of bedrock-
dammed lakes (e.g. Lake No. 513; Fig. 9c), or of moraine-dammed lakes with a
naturally high freeboard but without a natural surface outflow (e.g. Lake Safuna
Alta).
4. Siphon—Siphons are used to lower the water level before remedial work is
done (usually before open cut countersink or tunnel excavation is carried out),
however this is not a permanent solution. Figure 9d shows siphons installed in
2011 to lower the water level of Lake Palcacocha.
As shown above, sudden water release from Lake Palcacocha and Lake No. 513
occured despite the fact that they had been remediated. These lakes were chosen to
be remediated, because they were adjudged to be potentially hazardous, and thus
remedial work was done. If remedial work had not been done, the volume of
released water would have been much larger and thus the impacts would have been
248 A. Emmer et al.
more catastrophic. Water released from lakes of remediated dams should not be
interpreted as failure of the remedial works, but as improvement in hazard
assessment, because it is not entirely possible to prevent GLOFs only by remedial
work on the lake dam. Also, vulnerability mitigation such as urban planning based
on demarcation of potentially endangered areas should be done to eliminate
fatalities and significant material damages.
5 Conclusions
The number of potentially hazardous lakes within the Cordilllera Blanca is
increasing due to the ongoing glacier retreat and parallel glacial lake formation and
development in this heavily glacierized tropical range of the world. Furthermore,
the number of lakes is currently estimated to be more than one thousand within this
region and this number is still increasing. There are three types of glacial lakes
within the Cordillera Blanca which evolve with glacier retreat in altitudes between
Fig. 9 Examples of remedial works. Part ashows artificial dam and concrete outlet of lake Llaca
in the central part of the Cordillera Blanca; dam freeboard is 12 m. Part bcaptures ongoing work
on the dam of lake Rajucolta in 2004. Part cshows the entrance to the tunnel excavated in the
bedrock dam of lake No. 513 (red arrow). Part dshows six siphons installed in fall 2011 to drain
and lower the water level of lake Palcacocha
Glacier Retreat, Lakes Development and Associated Natural Hazards 249
4,600 m a.s.l. and 5,000 m a.s.l. These are: (1) bedrock-dammed lakes; (2) mor-
aine-dammed lakes; and (3) ice-dammed lakes. Significant lakes, having volumes
exceeding 10
6
m
3
of accumulated water, are of the first and second type, while ice-
dammed lakes do not reach this volume in the Cordillera Blanca. All types of
glacial lakes may produce glacial lake outburst floods, nevertheless lakes dammed
by Little Ice Age moraines are generally supposed to be potentially the most
hazardous in these days, because they are dammed by unstable moraines and are
frequently close to the present glaciers and the volume of accumulated water is
often great. Floods from any type of glacial lake are most commonly caused by
dynamic slope movements into the lake, producing displacement waves, which
breach or overflow the lake dam. The slope movements can be either direct or
indirect, and are associated with deglaciation. Dynamic slope movements are
mostly icefalls from hanging or calving glaciers or landslides of newly exposed
lateral moraines. These events claimed thousands of lives and caused significant
material damage within the Cordillera Blanca since the end of the Little Ice Age.
Presented examples of Lake Palcacocha, Lake No. 513 and Lakes Artizon Alto and
Artizon Bajo showed that the threat of GLOF is real and will require appropriate
and continued attention well into the 21st Century when glacier retreat continues
and even accelerates.
Acknowledgments The authors would like to thank Prof. Richard Crago (Bucknell University)
for the consultation and staff of Authoridad National de Agua (Huaráz) for scientific and logistic
support. The Grant agency of the Czech Republic (Project GACR P 209/11/1000) and Grant
agency of the Charles University (Project GAUK No. 70413) are acknowledged for financially
supporting this project.
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