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Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
1101
DOI: 10.4408/IJEGE.2011-03.B-119
DISASTROUS DEBRIS FLOWS CONNECTED WITH GLACIAL PROCESSES
AND DEFENSE METHODS AGAINST THEM IN KAZAKHSTAN
R.K. YAFYAZOVA
Hydrometeorological Center “Kazhydromet”
have the greatest scales.
rarely. However these debris flows have the great-
est scales. Debris-flow activity connected with gla-
cial processes is defined by scales of glaciations and
reaches its maximum in the phase of their degradation.
The area of glaciations in the Zailiysky Alatau makes
about 262 km
2
(Kudekov (ed), 2002). During degrada-
tion of glaciations the surface and subsurface reservoirs
are formed. Their breakout leads to formation of debris
flows. During degradation of glaciations under climate
warming rainfall-caused debris flows will become
more dangerous than debris flows connected with gla-
cial processes already in the 21st century (y
afyazova
,
ABSTRACT
Due to climate warming which came after the
ending of the Small glacial age, surface and subsur-
face reservoirs started to form on the mo - raine-gla-
cial complexes of the northern slope of the Zailiysky
Alatau Mountain Range. Breakout of these reservoirs
led to disastrous debris flows in the middle of the 20th
century. Up to 60s of the 20th century rainfall-caused
debris flows with rare frequency were considered to
be of main danger and construction of large check
dams forming debris-flow reservoirs was assumed as
a basis of defence strategy against debris flows. The
sharp activation of debris flows connected with glacial
processes required revision of the existing defence
strategy against debris flows. That is why designing
and building the small reservoirs for detention of
glacial outburst water in the high-mountain zone and
preventive measures aimed at emptying lakes on the
moraine-glacial complexes started.
K
ey
words
: moraine lake, debris flow, preventive measures
INTRODUCTION
The Zailiysky Alatau is one of the northern rang-
es of the Tien Shan Mountain system (Fig. 1). This
mountain range is characterized by the high debris-
flow activity. Rainfall-caused debris flows and debris
flows connected with glacial processes have the great-
est activity. Debris flows connected with earthquakes
take place very rarely. However these debris flows
Fig. 1 - The scheme of Tien Shan orography region 1 –
rivers; 2 – lakes; 3 – ranges
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5th International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment Padua, Italy - 14-17 June 2011
The first disastrous debris flow, caused by breakout
of lake No.17 located on the Zharsay glacier (the Issyk
River basin), happened on 6 July 1958. The volume
of debris flow made 4 million m3 (Popov, 1981). The
breakout of this lake happened through a underground
channel formed in the lake dam. The debris flow did
not cause the large damage, as it partially deposited
in lake Issyk located in the middle-mountain zone.
Debris-flow mass was mainly deposited on the sites
with slight slope of the Issyk River valley and the Is-
syk River debris cone adjoining to lake Issyk (Fig. 3).
During 1959-1962 the underground channel in
the lake dam was functioning, therefore the hollow
of lake No.17 located on the Zharsay glacier was not
filled by water. In autumn and winter 1962- 1963 the
underground channel was blocked and the hollow of
lake No.17 was filled by water again. On 7 July 1963
the disastrous breakout of this lake happened through
the same underground channel, as it was on 6 July
1958 (z
ems
, 1976). The water flow came out to the
surface outside the lake dam at a distance of about
100-150 m from this lake. Then it partially went into
a underground channel. The water flow moving on the
surface rushed down in a torrent gully. There it was
transformed into a debris flow. The water flow moving
on the underground channel wetted a moraine and the
landslide was formed on the frontal part of moraine.
It transformed into a debris flow and embodied with
the debris flow formed in the torrent gully. Further the
debris flow moved along the Zharsay River valley (it is
2003; y
afyazova
, 2007a; y
afyazova
, 2009).
The settlements (including Almaty city) with the
total population of about 2 million inhabitants are lo-
cated in the foothill zone of the northern slope of the
Zailiysky Alatau. In this connection the defense against
debris flows plays an important role in the sustainable
development of the Republic of Kazakhstan. In order to
decrease damage caused by debris flows, in the major-
ity of river basins of the northern slope of the Zailiysky
Alatau debris-flow-defensive constructions were built.
Preventive measuresare limited only preventive empty-
ing debris-flow dangerous lakes.
DEBRIS FLOWS CONNECTED WITH
GLACIAL PROCESSES ON THE NOR-
THERN SLOPE OF THE ZAILIYSKY ALA-
TAU IN THE 20TH CENTURY
Debris flows connected with glacial processes
formed due to breakout of surface and subsurface res-
ervoirs of moraine-glacial complexes. In the course
of degradation of glaciations the sizes of these reser-
voirs increase. On the northern slope of the Zailiysky
Alatau the degradation of glaciations began after the
Small glacial age. Formation of the large lakes on the
moraine-glacial complexes, which became debris-
flow dangerous, was recorded at the beginning of the
20th century (v
inoGRadov
, 1977). The basins of the
Issyk, Malaya Almatinka and Bolshaya Almatinka
Rivers are characterized by the most debris-flow ac-
tivity connected with glacial processes in comparison
with other river basins (Fig. 2).
Fig. 2 - The schematic map of the northern slope of
the Zailiysky Alatau The river basins: 1 – ka-
rakastek; 2 – Uzunkargaly; 3 – Chemolgan;
4 – kaskelen; 5 – Aksai; 6 – kargalinka; 7 –
Bolshaya Almatinka; 8 – Malaya Almatinka;
9 – Talgar; 10 – Issyk; 11 – Turgen. During
1959-1962 the underground channel in the
lake
Fig. 3 - The path of debris flows in 1958 and 1963 in
the Issyk River valley. 1 – the hollow of lake
No.17 on the Zharsay glacier; 2 – the torrent
gully; 3 – the Issyk river; 4 – lake Issyk
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DISASTROUS DEBRIS FLOWS CONNECTED WITH GLACIAL PROCESSES AND DEFENSE METHODS AGAINST THEM IN KAZAKHSTAN
Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
1103
debris flows connected with glacial processes in the
20
th
century, was the Malaya Almatinka River basin.
The first debris flow connected with glacial processes
occurred in this basin on 20 August 1951. It formed
due to breakout of lake No.2 on the Tuyuksu glacier
(C
HeRkasov
, 1953). The breakout of the lake hap-
pened through an underground channel. At that time
the lake was relatively small by volume (about 20
thousand m3). As the formed debris flow did not cause
the large damage, the conditions of its formation were
not studied (d
uysenov
, 1971; v
inoGRadov
, 1977).
On 7 August 1956 in the Malaya Almatinka
River basin a debris flow was formed due to break-
out of a subsurface reservoir located into the Tuyuksu
moraine-glacial complex. The volume of gushed wa-
ter was estimated at 1.5-2 million m
3
(v
inoGRadov
,
1977). The formed debris flow was accompanied by
a large and long postdebris- flow flood. At that time
Almaty city was not protected by the check dam but
was not damaged because the outburst water had the
discharge of about 30 m
3
/s only in its initial phase
(v
inoGRadov
, 1977). Fortunately, the water ran out
of the subsurface reservoir with the relatively small
gradually decreasing discharge, and therefore the de-
bris flow deposit did not reach Almaty city. Neverthe-
less, it caused other damage.
a tributary of the Issyk river), and then it moved along
the Issyk River valley down to lake Issyk (Figg. 3, 4).
The debris flow was entering into lake Issyk during
4 hours. Formation of waves on the surface of lake Issyk
together with increase of water level led to destruction of
the lake dam. Emptying of the lake Issyk with the vol-
ume of more than 18 million m3 lasted for a few hours.
The maximal discharge of outburst water was estimated
at 500-800 m3/s (d
uysenov
, 1971). The 1963 debris flow
had disastrous consequences. At the minimum, 54 men,
who had rested near lake Issyk, were killed. The damage
was large. The maximal discharge of debris flow made
7-12 thousand m
3
/s, the volume was 5.8 million m3, the
density of debris-flow mass made approximately 2400
kg/m3 (with the average density of solid component of
debris flow of 2650 kg/m3, the volumetric concentration
makes 85%) (z
ems
, 1976). The debris flow deposited ba-
sically in lake Issyk.
After the 1963 debris flow it became obvious, that
debris flows connected with glacial processes could be
disastrous and cause the large damage to settlements
located on the foothill plain adjoining the northern
slope of the Zailiysky Alatau. That is why the govern-
ment of the Republic of Kazakhstan made the decision
to speed-up designing and building of a check dam
to defend Almaty city against debris flows. The dam
formed a debris-flow reservoir with the volume of 6.2
million m
3
in the Medeo tract (k
HeGay
, 1988). In 1976
the volume of debris-flow reservoir was increased up
to 12.6 million m
3
.
In autumn and winter 1976-1977 the under-
ground channel in the lake dam was blocked again.
It led to filling the hollow of lake No.17 by water.
During spring and summer melting of snow and ice
the water level in the lake No.17 increased up to the
value, at which water overflowed through the lake
dam. The situation could be aggravated with open-
ing of the underground channel. It could lead to for-
mation of a disastrous debris flow. As the dam of
lake Issyk was destroyed in 1963, the debris flow,
which could form due to breakout of the lake on the
Zharsay glacier, could reach Issyk town unhindered.
It would lead to the large damage. The decision
about preventive emptying lake No. 17 was made.
This emptying prevented formation of a disastrous
debris flow (m
oCHalov
et alii, 1980a; m
oCHalov
et
alii, 1980b).
Another river basin, with sharp activation of
Fig. 4 - The torrent gully situated into the ancient mo-
raine of the Zharsay glacier. 1 – the torrent
gully; 2 – the landslide recess (right)
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R.k. YAFYAZOVA
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5th International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment Padua, Italy - 14-17 June 2011
torrent gully by 12-15 m (in some places by 40 m).
The debris flow destroyed two open-type dams in its
way (Fig. 7). The debris-flow 15-meter high wave en-
tered the debrisflow reservoir in the Medeo tract with
the discharge of about 10 thousand m
3
/s (Fig. 7). The
volume of debris flow made 3.8 million m
3
, and the
average density of debris-flow mass was 2400 kg/m
3
(with the average density of solid component of debris
flow of 2650 kg/m
3
, the volumetric concentration is
85%) (v
inoGRadov
, 1977). It is important to note that
in its way the debris flow entrained along in debris-
flow process not only by loose rocks, but also water
of various genesis, the main part of which made inter-
stitial water equal to 455 thousand m
3
. The volume of
interstitial water entrained along with soil in the debris
flow 2 times exceeded the volume of outburst water
from the lake.
The 1973 debris flow in the Malaya Almatinka
River basin caused the large damage. Due to filled
debris-flow reservoir by debris-flow mass by 60% Al-
maty city was unprotected against debris flows for a
few years (Fig. 8). The dam kept the debris flow and
By 15 July 1973 (the date of formation of a de-
bris flow) the volume of lake No.2 on the Tuyuksu
glacier increased up to 260 thousand m
3
. The water
level in the lake was sustained constant owing to wa-
ter overflow over the lake dam. The discharge of water
over the lake dam sharply increased, most probably,
as a result of drawing the lake dam caused by thawing
of buried ice. The opening in the lake dam increased
quickly because of erosive water flow (Fig. 5).
The maximal discharge of outburst water was
about 350 m
3
/s. The volume of water which poured
out from the lake made about 224 thousand m3. De-
bris-flow mass, formed on the frontal part of modern
moraine, decayed on the glacial-carved valley on the
path to a dam in the Mynzhilki tract. As the volume
of reservoir formed b the dam was only about 10% of
the volume of the glacial outburst water, the dam was
destroyed within 3 minute (Fig. 6). Having breached
the dam, the water flow rushed down in a torrent gully
in the ancient moraine. The debris flow passed 8-kil-
ometer to the check dam in the Medeo tract in 12-13
minute (its velocity was 10- 11 m/s). It deepened the
Fig. 5 - Lake No.2 after its breakout in 1973
Fig. 6 - The dam opening after the 1973 debris flow in
the Mynzhilki tract
Fig. 7 - The open-type dam destroyed by the 1973 de-
bris flow
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DISASTROUS DEBRIS FLOWS CONNECTED WITH GLACIAL PROCESSES AND DEFENSE METHODS AGAINST THEM IN KAZAKHSTAN
Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
1105
soils participating in debris flow-forming are similar
to soils of ancient moraines in the Zailiysky Alatau).
On 19 August 1975 debris flow was formed due to
breakout of lake No.14 located on the Kumbel glacier
(the Bolshaya Almatinka River basin). The maximal
discharge of debris flow did not exceed 160 m
3
/s. The
density of debris-flow mass reached 2500 kg/m
3
(with
the average density of solid component of debris flow
of 2650 kg/m
3
, the volumetric concentration makes
91%) (k
iRenskaya
et alii, 1977). Owing to the high
density of debris-flow mass the velocity of debris flow
(the maximal depth of debris flow equal to 5.6 m) did
not exceed 2 m/s. The traces of debris flow are shown
in Fig. 10. For debris flows with the low velocity are
characteristic the following: pronounced boundary of
debris flow surface; the absence of an aerosol mud
cloud above a debris flow; little skewing of the debris-
flow surface at bends (k
iRenskaya
et alii, 1977).
On 3 August 1977 in the Bolshaya Almatinka
River basin during preventive works on lake No.13
located on the Sovetov glacier breakout of the lake
happened and disastrous debris flow was formed
(P
oPov
et alii, 1980). As a result of failure of the lake
dam water with volume of 74.5 thousand m
3
was dis-
thereby it saved the eastern part of Almaty city from
destruction. Unfortunately, 70 men who were up-
stream of the check dam were killed (k
HeGay
, 1988;
y
afyazova
, 2007b).
According to the technical report, measuring char-
acteristics of the 1973 debris-flow deposits surface in
the debris-flow reservoir in the Medeo tract, showed
that at a distance of 350 m from the dam (the average
depth of 50 m) the slope of debris-flow deposits surface
did not exceed 0.3º; at a distance of 350-450 m (the
average depth of 40 m) it was close to 0.7º; at a distance
of 450-550 m (the average depth of 30 m) it increased
nearly to 1º and only at the next following 200 m (the
average depth of less than 20 m) it increased almost
to 2º. The fact that debris-flow deposits surface forms
slight slope while depth exceeds tens of meters in the
debris-flow reservoir is of the great importancewhen
debris-flow reservoirs are designed (Fig. 9).
The 1973 debris flow confirmed the results of ex-
periments on artificial replication of debris flows car-
ried out by the Kazakh Research Hydrometeorological
Institute in the Chemolgan River basin in the period
1972-1978 (s
tePanov
& s
tePanova
, 1991).
It was found out, that mixture of debris-flow mass
during movement of debris flow was kept up to values
of concentration of solid component in debris-flow
mass, much more exceeding values of concentration
known earlier (s
tePanov
& s
tePanova
, 1991). Just
being mixture, when the concentration of solid com-
ponent in debrisflow mass is large, conditioned an op-
portunity of formation of debris-flow mass with the
density of more than 2400 kg/m
3
(it is possible, when
granulometric and mineralogical compositions of
Fig. 8 - The debris-flow reservoir filled by the 1973
debris-flow mass in the Medeo tract
Fig. 10 - Traces of the debris flow of 19 August 1975 in
the Bolshaya Almatinka River basin
Fig. 9 - The 1973 debris-flow deposits surface in the
reservoir whichformed by dam
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5th International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment Padua, Italy - 14-17 June 2011
charged from the lake during 1 hour 25 minute. The
average discharge of water through the opening in the
lake dam was 15 m
3
/s, and the maximal discharge of
water exceeded 30 m
3
/s (Fig. 11). The solid compo-
nent of debris flow, formed on the modern moraine,
was mainly deposited on the glacial-carved valley at a
height of more than 3000 m a.s.l., located above a tor-
rent gully. The liquid component of debris flow, con-
taining in its composition the insignificant amount of
suspended particles, entered the torrent gully.
The deepening the torrent gully and the collapsing
its sides led to the outlet onto the day surface of nu-
merous underground springs. It resulted in the signifi-
cant increase of discharge and volume of debris flow
on 3 August. On subsequent days numerous formation
of debris flows with the relatively small volume took
place as a result of instability of sides of the torrent
gully. However short-term formation of debris flow
with the maximal discharge of about 10 thousand
m3/s took place on 4 August.
According to various estimations, over the period
3-31 August the total volume of debris flows varied
from 2.4-3.2 million m
3
(P
oPov
et alii, 1980; o
siPova
& k
azannikov
, 1982) to 6 million m
3
(Y
esenov
& d
e
-
Govets
, 1979). Debris-flow events happened on 3-31
August 1977 in the Bolshaya Almatinka River basin
caused the large damage, people were killed.
As a result of debris-flow events on 3-31 August
1977 researchers made up a conclusion that intense
wetting (more than 15%) moraine can turn 1 m3 of
water into 60 m
3
of debris-flow mass. Such ratio is
applicable when wet soil is on yield stress, and granu-
lometric and mineralogical compositions of soil are
similar to soil of ancient moraines in the Zailiysky
Alatau (s
tePanova
, 1989).
During the 20
th
century debris flows connected
with glacial processes were formed also in the other
river basins of the northern slope of the Zailiysky Ala-
tau, but they had no disastrous character.
DEFENCE AGAINST DEBRIS FLOWS
CONNECTED WITH GLACIAL PROCES-
SES
The necessity of defense against debris flows of
Almaty city was realized in the second half of the
19th century (k
HeGay
, 1988). The relevance of this
problem was confirmed by the event of 1921 when the
eastern part of Almaty city was destroyed; about 500
people were killed due to a rainfall-caused debris flow.
As till 60s years of the 20
th
century it was considered,
that rainfall-caused debris flows, which had rare fre-
quency, represent the main danger, the construction of
large check dams forming debris-flow reservoirs (with
the volume of about 10 million m
3
) was assumed as
a basis of defence strategy against debris flows. The
sharp activation of debris flows connected with glacial
processes required revision of the existing defence
strategy against debris flows. That is why designing
and building the small reservoirs in the high-mountain
zone (with the volume of about 200 thousand m
3
) for
detention of glacial outburst water and carrying out
measures on preventive emptying lakes on the mo-
raine-glacial complexes were begun.
In the period 1964-1966 the using siphons for
maintenance of the safe water level in lake No. 2 lo-
cated on the Tuyuksu glacier (the Malaya Almatinka
River basin) is the beginning of preventive measures
for prevention and mitigation of consequences of
debris flows connected with glacial processes in Ka-
zakhstan. Due to difficult servicing the siphons their
work was stopped with the beginning of construction
of the check dam in the Medeo tract. Preventive emp-
tying surface reservoirs on the moraine-glacial com-
plexes in the basins of the Issyk, Malaya Almatinka
and Bolshaya Al-matinka Rivers became the follow-
ing stage in the realization of preventive measures.
Preventive emptying lake No. 17 located on the
Zharsay glacier (the Issyk River basin) in 1977 is the
first successful experience in prevention of formation
of disastrous debris flows connected with glacial proc-
esses in Kazakhstan. In 1977 the hollow of lake No. 17
Fig. 11 - Lake No.13 after its breakout in 1977. 1 –
opening in the lake dam; 2 – the hollow of lake
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DISASTROUS DEBRIS FLOWS CONNECTED WITH GLACIAL PROCESSES AND DEFENSE METHODS AGAINST THEM IN KAZAKHSTAN
Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
1107
water flow happened through the surface channel with
the discharge to 29 m
3
/s. The prevention of disastrous
flood which (as it was considered) could formed dur-
ing displacement of water from the lake due to the fast
movement of the Bogatyr pulsative glacier was by the
purpose of preventive emptying this lake. The evacua-
tion channel was formed by explosion. The explosive
was tamped in the holes, which were located along the
planned evacuation channel at a depth of from 3 to 11
m. The total weight of an explosive was about 14 tons.
As a result of explosion the frozen moraine soil and
buried ice of about 10 thousand m3 was ejected from
the lake dam. The gradual increasing the water dis-
charge to 105 m
3
/s was observed in the channel within
6 hours. Then the water discharge gradually decreased.
The emptying lake No. 9 lasted about two days. The
volume of the water was decreased by 6.2 million m3,
the water level was lowered by 14.5 m. The evacuation
channel was deepened by 15-20 m due to thermal and
mechanical erosion, and its throat advanced into the
lake by 200 m (b
izHanov
et alii, 1998).
In 1997 lake No. 6 located on the Manshuk Mame-
tova glacier (the Malaya Almatinka River basin) was
recognized the most dangerous moraine lake on the
northern slope of the Zailiysky Alatau. Preventive
emptying this lake has a long history. In the second
half of the last century some attempts for its preventive
emptying were carried out for decreasing the volume
of the lake to a safe water level. The first attempt for
its emptying was carried out in the period 1976-1978,
when the volume of the lake was about 40 thousand
m
3
. As a result of the performed work the volume of
the lake was reduced to 36 thousand m
3
(b
izHanov
et
alii, 1998). The second attempt for its emptying was
carried out in 1997. At this time the volume of the lake
was about 190 thousand m
3
. According to the technique
of emptying the lake it was supposed, that decreasing
overflow crest of channel on the lake dam by washing
away and transporting moraine soil will be carried out
by using water energy. It was supposed to carry out
by discharges water from the lake by means of «soft
(made of tarpaulin) and «rigid» (made of metal) gates.
The shortterm discharges of water with the discharge
of 10-12 m
3
/s were formed by “soft” gate for destruc-
tion of stone riprap. The stone riprap was formed after
every discharge water. The long-term discharges water
with the discharge of 3-4 m
3
/s were formed by «rigid»
gate for deepening the channel. The non-observance of
was filled again by water. The hollow was filled and
empted with formation of the disastrous debris flows
in 1958 and 1963. As having surface overflow water
through the lake dam was inevitable (in the lake the
water level was increased by approximately 0.5 m pe
day), and breakout of underground channel with the
disastrous discharge of water could happen within the
next few days, the decision was accepted to make use
by the surface channels formed still in 1963 for con-
trollable empting the lake. For this purpose the moraine
soil was got out of the surfaces of channels. Having
over - flow water on these channels led to their gradual
deepening. The regulation of intensity of thawing of
ice in the channels was carried out by cleaning of soil
in the channels. As a result of the described measures it
was possible to carry out controllable discharge water
equal to more than 200 thousand m3 from lake and to
ensure further spontaneous empting of 220 thousand
m3 of water The average discharge of water through
the lake dam made about 1.8 m3/s, and the maximal
discharge was 6-8 m
3
/s (m
oCHalov
& s
tePanov
, 1980;
s
tePanov
et alii, 2001).
By the beginning of August 1977 the moraine soil
adjoining to the channel unfreeze due to land reclama-
tion work and the thermal effect of water flow. On 3
August when the water level in the lake rising by 0.7
m relative to the natural overflow crest of channel the
spontaneous destruction of embankment happened and
a debris-flow process began directly on the lake dam. It
led to disastrous empting the lake. An initial phase of
destruction of the lake dam was not observed (P
oPov
et
alii, 1980; s
tePanov
et alii, 2001).
Preventive emptying lake No.9 located on the
Bogatyr glacier (the Chilik River basin) was the most
scale preventive measure. The Chilik River basin is
located on the southern slope of the Zailiysky Alatau,
the northern slope of the Kungey Alatau, and the east-
ern slope of the Chilik-Kemin cross connection. Lake
No.9 is located at a height of 3460 m a.s.l. In 1985
before the beginning of preventive measure the lake
was as long as 1,850 m, as wide as 670 m, with the
average depth of 13.3 m and the maximal depth of 34.9
m. The area of water surface of the lake was 690 thou-
sand m
2
and its volume was 9.3 million m
3
. The lake
dam was combined the frozen moraine soil and buried
ice. The temperature of frozen moraine soil changed
from 0 to -3.3 ºС at a depth from 3 to 10 m. In summer
period, when the water level in the lake was maximal,
background image
R.k. YAFYAZOVA
1108
5th International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment Padua, Italy - 14-17 June 2011
plexes
At the present time the most dangerous lake in the
Zailiysky Alatau is lake No. 6 located on the Manshuk
Mametova glacier. Its volume is about 230 thousand
m
3
. According to existing estimations, the volume of
debris flow, which can be formed during breakout of
this lake, can exceed 10 million m
3
. This is commen-
surable with the volume of the debris-flow reservoir
which was constructed in the Medeo tract for defence
against debris flows of Almaty city. The overflow of
the debris-flow reservoir can lead to destruction of the
eastern part of Almaty city.
Aforesaid concerns to dangerous surface res-
ervoirs. At the same time subsurface reservoirs of
moraine-glacial complexes are represented not the
smaller danger. In Kazakhstan there are no meth-
ods for detection of subsurface reservoirs and their
preventive emptying. So, the 1956 debris flow was
formed the Malaya Almatinka River basin due to brea-
kout of the subsurface reservoir located into the Tuy-
uksu moraine-glacial complex. If the total outlet water
transformed into debris flow, no one dam constructed
in the valleys of the northern slope of the Zailiysky
Alatau by the present time could not check it.
As a reduction of sizes of moraine-glacial com-
plexes due to climate warming in the Zailiysky Alatau
rainfall-caused debris flows will become more dan-
gerous than debris flows connected with glacial proc-
esses (y
afyazova
, 2009).
DISCUSSION AND CONCLUDING RE-
MARKS
The defence against debris flows of the settle-
ments located on the foothill plain adjoining to the
northern slope of the Zailiysky Alatau is based on
the scientific consideration about debris flows in the
middle of the last century. The results of researches
carried out in the last decades testify to significant in-
consistency of protection rate of these settlements to
the real threats which debris flows create under the cli-
mate conditions in the 21
st
century (y
afyazova
, 2009
y
afyazova
, 2010). During recent decades the reality
of global warming has been confirmed. For the Tien
Shan region warming is causing significant decrease
in the area and volume of glaciers, enhancing perma-
frost thaw, relocating the forest boundary along moun-
tainsides to higher altitudes, increasing the number
of glacial lakes and associated breakout floods, and
the technique led to formation of stone riprap, which
the water flow with the discharge of 10-12 m
3
/s could
not destroyed. Due to the water level in the lake was
lowered by 2.6 m in place of planned of 5 m.
During the past decades the preventive emptying
of some debris-flow dangerous lakes was made in the
other river basins of the northern slope of the Zaili-
ysky Alatau. However these lakes had the small vol-
umes and did not represent the large threat.
The building dams in the high-mountain zone
for detention of water flows formed during breakout
of moraine lakes is a very effective way for defence
against debris flows connected with glacial processes
in the Zailiysky Alatau. In the high-mountain zone the
valleys are characterized relatively slight slopes and
large width. The dam forming a reservoir for deten-
tion of glacial outburst water in the Mynzhilki tract
at a height of 3000 m a.s.l. is an example of building
dams in the high-mountain zone. The volume of reser-
voir is 230 thousand m3. On the efficiency this dam is
equivalent to a dam forming a reservoir for detention
of debris-flow mass with the volume of about 4 mil-
lion m
3
and located at a height of 1700-1800 m.
DEBRIS-FLOW DANGER CONNECTED
WITH GLACIAL PROCESSES AT PRE-
SENT TIME
Due to global climate warming there is an inten-
sive thawing of glaciers on the northern slope of the
Zailiysky Alatau. For 35 years the area of glaciers
decreased by 30% (v
ilesov
, 1997). The most likely,
by the end of the 21
st
century in the Zailiysky Ala-
tau the glaciers will disappear (v
ilesov
, 1997). How-
ever within the next decades the danger of formation
of debris flows connected with glacial processes can
even be increased. The existing methods for preven-
tive emptying moraine lakes will allow to avoid the
large material damage and to keep health and life of
people. However the preventive emptying of moraine
lake is not a unique way for prevention of debris flows
connected with glacial processes. Existing experience
of glacial monitoring allows to assert, that the preven-
tion of occurrence and development of surface reser-
voirs on the moraine-glacial complexes is the most
effective and safe way for prevention of debris-flow
danger. Unfortunately, till now in Kazakhstan the due
attention is not given to prevention of occurrence and
development of lakes on the moraine-glacial com-
background image
DISASTROUS DEBRIS FLOWS CONNECTED WITH GLACIAL PROCESSES AND DEFENSE METHODS AGAINST THEM IN KAZAKHSTAN
Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
1109
measures based on the sizes of debris flows in the pas
century will not provide reliable protection. The de-
velopment of a defensive strategy against debris flows
under climate warming is a prerequisite for the sus-
tainable development of the Republic of Kazakhstan
increasing rainfall-induced debris flows activity. In
this region, the defense strategy against debris flows
is based on the frequency of rare, large debris flows
typical under the climate conditions of the 19-20th
centuries. Therefore, under global warming defensive
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Statistics