Snow Avalanche Incidents in North-Western Anatolia, Turkey during

Natural Hazards 11: 1-16, 1995.
0 1995 Kluwer Academic Publishers. Printed in the Netherlands.
Snow Avalanche Incidents in North-Western
Anatolia, Turkey during December 1992*
IBRAHIM G ~ J R E R
Gazi University, Engineering and Architectural Faculty, Department of Civil Engineering, Maltepe,
Ankara, Turkey
HARUN TUNCEL
Ankara University, Faculty of Language, History and Geography, Department of Geography, Slhhiye,
Ankara, Turkey
0. M U R A T Y A V A S and T A R H A N E R E N B I L G E
General Directorate of Disaster Affairs, Lodumlu, Ankara, Turkey
and
AYHAN SAYIN
Turkish State Meteorological Service, Kalaba, Ankara, Turkey
(Received: 17 June 1993; in final form: 26 October 1993)
Abstract. Snow avalanches take place in the mountainous regions of Turkey mostly in the eastern
Anatolia Region with an average annual death toll of 23 people and much damage to property.
However, in the mountainous areas of the Kastamonu and Sinop provinces in the western part of the
Black Sea Region of Turkey between 25 and 30 December 1992, blizzards with heavy snowfall caused
roof collapses and major avalanche events whereby 16 people were killed and 2 injured. When past
records were investigated, there was no evidence that avalanche accidents had been encountered in
the region where the dominant precipitation type is rain in the coastal zones and snow over the
mountains. Moreover, avalanche prevention measures are so limited that the resettlement of villages
or hamlets located in risk zones is common practice. In this article, avalanche formation associated
with the meteorological conditions and geomorphologic features is discussed.
Key words. Snow avalanches, north-western Anatolia, Turkey, avalanche prevention measures
1. Introduction
Turkey is located between 36-42" N latitude and 26-45" E longitude with varying
climatological features, covering an area of 780 000 km2 and having a population
of 60 million, according to the 1990 census. There are mountain ranges running
parallel to the coast of the Black Sea at the north and the Mediterranean Sea at
the south and comparatively high mountains and plateaus at the eastern part of
* This study was partially supported by Tiibitak (Scientific and Technical Research Council of Turkey)
with Project No. YBAG-0067.
2
IBRAHIM G ~ J R E RET AL.
Table I. Statistical data of the avalanche incidents in Turkey between 1950 and 1993' (Giirer et al.,
1993)
Winters
Number of
events
Death toll
Number of
injured people
Number of
rebuilt houses
1992-1993
1991-1992
1990-1991
1989-1990
1988-1989
1987-1988
1986-1987
1985-1986
1984-1985
1983-1984
1982-1983
1981-1982
1980-1981
1979-1980
1978-1979
1977-1978
1976-1977
1975-1976
1974-1975
1973-1974
1972-1973
1971-1972
1970-1971
1969-1970
1968-1969
1967-1968
1966-1967
1965-1966
1964-1965
1963-1964
1961-1962
1959-1960
1958-1959
1955-1956
1954-1955
1952-1953
1949-1950
31
112
12
4
7
13
10
2
2
6
14
10
4
9
2
10
9
135
328
7
4
4
27
18
1
7
6
15
14
4
3
1
170
2
59
95
53
146
1656
267
47
77
365
146
16
29
94
400
117
52
102
119
145
368
97
17
12
35
65
51
156
15
18
43
18
34
15
-
5
2
2
1
3
4
9
1
1
2
3
4
1
-
21
-
28
7
1
7
9
6
3
2
1
8
4
-
1
-
33
-
17
7
-
4
-
-
" Based on the archives of the General Directorate of Disaster Affairs of Turkey.
the Anatolian peninsula. There have been drastic increases in snow avalanche
incidents during the last decade in Turkey, culminating in 112 events and 328
death during the winter of 1991-1992 (Table I). In this paper, the western part of
the Black Sea Region (Figure 1) was chosen as the study area because of the fact
that several major snow avalanches took place in the region, as well as in other
parts of Turkey, due to more severe winter conditions than in previous years
(WMO, 1993). Time series of monthly accumulated snow depths in December of
Study Area
District Center
171
1
Meteorological Station
N
SS~OW
Avalanche Areas
Road
Fig. 1. Location map of the Kastamonu and Sinop avalanche regions in the western Black Sea Region.
the period of 1966-1992 at one of the nearest meteorological stations P~narbag~,
are given in Figure 2. As the figure depicts, the maximum snow accumulation was
recorded as 120 cm in 1992. Comparing with the period of 1966-1991 during which
the maximum measured snow depth was 40 cm with a minimum of 6 cm, and an
average value of 15 cm, the December 1992 total snow depth was eight times
higher than the previous average value. In the western part of the Black Sea
Region, the coastal zone has a mild climate. However, moving inland, it changes
abruptly and heavy snowfalls occur over the mountains during the winter. The
Kiire (Isfendiyar) mountain ranges (Figure 1) with a peak of 1885 m at Yaraligoz
location are dissected by deep valleys and the inhabitants are usually settled in
IBRAHIM GURER ET AL.
Fig. 2. Variation of maximum snow depths for December from the Plnarbay Meteorological Station
during the period of 19661992.
villages located in valleys prone to snow avalanches. About 42% of the area is
covered with beech forest, and the total amount of annual precipitation ranges
between 1000 and 1500 mm. In the region, a series of major snow avalanches
occurred in December 1992, due to severe winter conditions, killing 13 people,
injuring two, and causing an estimated property loss of about US$500 000 (Table
11).
The purpose of this paper is to investigate avalanche incidents that took place
in the western Black Sea Region during the period of 25-30 December 1992, as
a case study.
Following the extreme snow events, three field studies were carried out on 28
December 1992, and 8 and 21 January 1993. Only two avalanche locations, in the
area of the Kayaarkasi, Seyhoglu, and Catakgiiney villages of Kastamonu province, could be studied, since it was not possible to reach the avalanche district
due to stormy weather and bad road conditions. During the field trips, hydrometeorological data were compiled from nearby meteorological stations. However,
5
SNOW AVALANCHE INCIDENTS IN NORTH-WESTERN ANATOLIA, TURKEY
Table 11. Tabulation of extreme snow accumulation events and damages in northwestern Anatolia
during 25-30 December 1992
Location
Kastamonu-Kiire
Topqular (Kayaarkas~)
Kastamonu
Devrekani-BeIova
Kastamonu-SenpazarAyvatan
Sinop-Tiirkeli
Catakgiiney
Kastamonu-BozkurtSeyhoglu (Dereyolu)
People
Property loss
killed injured
house
Type of events
Date of occurrence
stock
Avalanche
25.12.1992
5
2
8
108
Snow Blizzard
28.12.1992
2
-
-
?
Roof Collapse
28.12.1992
1
0
1
?
Avalanche
29.12.1992
5
0
5
?
Avalanche
30.12.1992
Total
3
16
0
2
3
17
5
?
these stations are generally located in city or town centers, not reflecting the true
weather conditions in the remote villages where these avalanches took place.
Moreover, the study team measured such important parameters as snow depth,
density, and water equivalent of the avalanche zones during the field investigations.
Subsequently, compiled hydrometeorological, topographical, and geological data
are presented as a case study.
2. Geology-Geomorphology of the Disaster Area
The Kure mountains face the Black Sea and are located in the northwestern part
of Turkey. The study area is situated between Kastamonu city in the south and
the Black Sea in the north, Zonguldak in the west, and Sinop in the east, extending
about 50 km in N-S and 75 km in E-W directions (Figure 1). In the northeastern
part of Daday, Triassic limestone are seen transitive with other younger limestones. Liassic formations between the Azdavay Region mountain areas include
marls and partially metamorphosed dark colored shales which are cut by basalt
dykes. Upper Jurassic-Lower Cretaceous are found in the Kure mountain region
( ~ l h a n ,1976). In the vicinity of Kiire, granite and diorites which are of Alpine
origin are seen with metagraywackes. In addition to these rocks, radiolarites and
ophiolites of Paleocene are also seen locally in the region (Campbell, 1971). When
the study area is examined from the geomorphologic point of view, it is seen that
the mountains are flat topped with slopes of between 20-60" of middle Miocene
peneplain and Upper Miocene sediments of limestone with a stage of structural
evolution which influenced the landforms of folded Mesozoic (Erol, 1991). The
area is divided by a dense network of valleys and is covered by Fagus Orientalis,
Pinus Nigra and Pinus Silvestris.
6
IBRAHIM G ~ J R E RET AL.
Fig. 3(a).
Fig. 3. Surface and 500 hPa charts at 00 GMT on 21 and 25 December 1992.
3. Meteorological Conditions
When the meteorological conditions prior to the avalanche events are examined,
snowfall started on 12 December 1992 and continued intermittently until 19 December. During this period, recorded daily maximum and minimum temperature
values were 7 and -8°C at the study area (elevation = 650 m a.m.s.l.), respectively; prevailing wind directions were northerly (N) and southerly (S); and surface
wind speed was light. Daytime temperatures over 0°C caused a thawing of the
snow and kept the soil mantle with a rather high moisture content. Moreover,
surface melting of snow cover during daytime and freezing during night created a
hard crust at the top of the snow layers.
As depicted in the surface and 500 hPa charts of 21 December 1992 (DMI,
1992) (Figures 3a and 3b), a high pressure center was located over Turkey at
the surface, indicating fair weather conditions but fog and, consequently, no
precipitation was recorded. The surface temperatures were between 0 and 3°C
during daytime and 0 and -17°C during the night. Surface prevailing wind direction was northerly (N), light or calm.
During the period of 22-25 December 1992, the passage of a family of depres-
SNOW AVALANCHE INCIDENTS IN NORTH-WESTERN ANATOLIA, TURKEY
7
Fig. 3(b).
sions associated with cold and warm fronts brought heavy precipitation in the form
of snowfalls with depths of more than 2 m and even greater at some remote
locations (Figure 3c and 3d). The same meteorological conditions continued until
the end of December.
Field investigation showed that the triggering effects of snow avalanches were
as follows: fresh snowfalls over old snow which had a 25 cm thick crust, strong
winds (gusty) which were not recorded by nearby meteorological stations but
mentioned by local people just before the avalanche and recorded temperatures
that were below zero degrees Celsius. Consequently, the fresh snow on the hills
slid through the forest openings on the south facing slopes down to the villages,
killing several people and causing much damage to property.
The depth, density, and water equivalent values of the snowpacks in the two
avalanche zones measured during the field studies, are given in Table 111.
Since it was not possible to collect the meteorological data at exact avalanche
locations, the Pinarbasi meteorological station, among others, was chosen to give
an idea of the meteorological conditions in the region (Table IV). During the
same period of avalanche events, the recorded maximum snow depths at various
meteorological stations were as follows: 120, 150,29,73 cm at Pinarbagi, Azdavay,
Daday, and Devrekani, respectively. It is interesting to note that a quite large
8
IBRAHIM GiJRER ET AL.
Fig. 3(c)
variation of snow depths within the same sub-climatological regions justifies the
possibility of having snow depths as high as 4 m on leeward slopes and strong
winds mentioned by local people during interviews in the avalanche zone. The
tabulation of the snow depth (cm), surface air temperature ("C), and wind speeds
(mlsec) at 07h00,14h00, and 21h00 of local time; and daily maximum and minimum
temperatures and snow depth variations are presented in Table IV and in graphical
form in Figure 4.
Case 1. Avalanche in Kayaarkass Village
Kayaarkasi village is located in the northern part of Kastamonu province. The
avalanche path slopes from the northeast towards the southwest (Figure 5 ) and
its slope angle, measured by inclinometers, varies between 28 and 35". Above the
village at the starting point of the avalanche, there used to be a dense forest of
Orientalis and Quercus Aegilops (Gokmen, 1962), but this has been destroyed
by inhabitants for heating and construction material over many years. Thereby,
currently, there is only a small belt of forest extending between 700 and 750 m
(Figure 6).
Prior to the avalanche release, outside the avalanche path, the accumulated,
9
SNOW AVALANCHE INCIDENTS IN NORTH-WESTERN ANATOLIA. TURKEY
Fig. 3(d).
Table 111. Tabulation of the depth, the density and the water equivalent of the snowpack at two
avalanche locations
Location
Kastamonu, Kiire,
Top~ular,Kayaarkasi
Kastamonu, Bozkurt,
Seyhoklu (Dereyolu)
Observation
Date
Depth
s d (cm)
Density
s d (kg/m3)
Water Eq.
SWle(cm)
29.12.1992"
195 (outside)
120 (at the center)
150
283
29.3
34
21.01.1993~
>6 m (at toe)
-
?
" Field investigation carried out three days after the avalanche.
Investigation carried out 22 days after the avalanche.
undisturbed snow depth was of 195 cm. Actually, permanent snow cover had
started on 15 December, subsequently it melted and refroze forming a crust, thus
creating favorable conditions for the avalanche release. Table IV and Figure 4
show the time series of the meteorological parameters of the nearby meteorological
station of the avalanche zone.
The avalanche mass under the effects of dynamic forces slid from the 1100 m
high hill toward the village at an elevation of 650 m on 25 December 1992 at 8
a.m., killing five people and 108 cattle, injuring two persons and damaging eight
houses out of 25.
10
IBRAHIM GURER ET AL.
Table IV. Tabulation of the available relevant climatological data of P l n a r b a ~meteorological
~
station,
during 22-31.12.1992. P l n a r b a ~ ~h(e1evation)
,
= 650 m location: 41°36' N-33"07' E
Date
Snow depth
(cm)
Temperature ("C)
07h00
14h00
Wind direction and speed
(mtsec)
21h00
07h00
14h00
21h00
Case 2. Avalanche in Dereyolu Village
Located in the northern part of Kastamonu province, Dereyolu village is surrounded by hills which are mainly covered with Fagus Orientalis forest, although
trees in the avalanche path have been destroyed by local people and goats. The
descending zone of the avalanche mass starts at 1640 m and ends at 800 m (Figure
7) with a path length of 2000m and the slope angles of the path, measured by
inclinometers, were 55-60, 40, and 20" at the upper, middle, and lower parts,
respectively. The width of the path was in the range of 20-50 m with a depth of
snow and debris 6 m at the toe of the avalanche (Figure 8).
As in the first case, Table IV and Figure 4 show the time series of the meteorological parameters. Information obtained from the local people on the accumulation of the 4 m snow depth, along with blizzard prior to the avalanche event,
indicate much worse conditions than those concluded from the meteorological
measurements.
The avalanche, released with a thunder and burst of clouds, killed three people,
damaged three houses completely and five partially, and caused some loss of
livestock. The following measurements are good indicators of the destructive
power of the avalanche. The estimated surface area was of 60 000 m2 with a volume
of 75 000 m3 of material.
Conclusion
Major snow avalanches took place in north-western Anatolia during the period of
25-30 December 1992, killing 13 people and livestock, injuring two people and
damaging 17 houses. This was due to the facts that the 1992 winter conditions in
Turkey were colder and more stormy than in previous years, and there has been
a fast depletion of the forest canopy over the years, and there has been a lack of
SNOW AVALANCHE INCIDENTS IN NORTH-WESTERN ANATOLIA. TURKEY
11
Dates
Fig. 4. Snow depth, maximum and minimum temperature variations at the Plnarba~iMeteorological
Station during 2 4 3 1 December 1992.
IBRAHIM GiJRER ET AL.
Fig. 5. Topographical map and avalanche path of the Kastamonu-Kayaarkas~avalanche.
SNOW AVALANCHE INCIDENTS IN NORTH-WESTERN ANATOLIA, TURKEY
13
Fig. 6. The Kastamonu-Kayaarkas~avalanche region.
avalanche prevention measures, etc. In addition, two people were lost in blizzards
and one house collapsed because of a heavy snow load, killing one person. Also,
it is quite interesting to note the seriousness of the scope of the avalanche hazard
in the region because local records showed that no avalanche events have occurred
during the last 100 years. Because of the harsh winter conditions coupled with a
deteriorated forest canopy and land use, fatal avalanche events took place which
caused much damages. Therefore, it is extremely urgent to take the following
precautions to prevent avalanche accidents in Turkey:
IBRAHIM GURER E T AL.
Fig. 7. Topographical map and avalanche path of the Kastamonu-Dereyolu avalanche.
SNOW AVALANCHE INCIDENTS IN NORTH-WESTERN ANATOLIA, TURKEY
15
Fig. 8. The Kastamonu-Dereyolu avalanche region.
(1) Avalanche risk maps should be prepared because of the fact that avalanche
incidents occur not only in the western Black Sea Region, as investigated
in this paper, but also mostly in the mountainous regions of eastern Anatolia
where the annual frequency is around nine cases, which is much higher than
in the rest of the country.
(2) Depending on the particular avalanche zone requirements, proper prevention measures such as tunnels, snow racks, snow bridges, and artificial
IBRAHIM G ~ ~ R EE R
T AL.
avalanche release, should be taken by responsible organizations together.
Moreover, the current common policy for avoiding danger from avalanches
is to evacuate the endangered villages, hamlets, or building if deemed
necessary by the state.
(3) There is no responsible. organization to deal directly with avalanche forecasting. The State ~ e t e o r o l o ~ i c aService
l
issues heavy precipitation warnings in addition to its daily and weekly weather forecast information, yet
it is not sufficient for avalanche forecasting. Also, meteorological stations
are located in cities or do not represent real meteorological conditions in
avalanche zones. Thus, avalanche observation networks and a department
of the State Meteorological Service for avalanche forecasting should be
established.
(4) Training of staff, as well as local people who live in areas prone to avalanche
hazard, should be undertaken immediately. Pioneering work has been initiated by the General Directorate of Disaster Affairs and priority has been
given to local awareness.
(5) Presently, there are no rescue teams for special avalanche missions. In
general, rescue efforts are disorganized and conducted by untrained state
workers using unsuitable equipment which mainly consists of heavy construction machines that sometimes cause undesired death of victims. Consequently, proper rescue teams should be established on a regional basis.
References
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