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Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
965
DOI: 10.4408/IJEGE.2011-03.B-105
ASSESSMENT OF A MUDFLOW HAZARD ON THE BLACK SEA COAST
OF CAUCASUS AND IN THE ADJACENT MOUNTAINOUS AREAS
i.v. MALNEVA
(*)
&n. k. KONONOVA
(**)
(*)
All-Russian Research Institute for Hydrogeology & Engineering Geology (VSEGINGEO),
Noginsk District, Moscow Region, Russia - Email: irmaln@rambler.ru
(**)
Geography Institute of RAS, Moscow, Russia - Email: NinaKononova@yandex.ru
struction of different structures, including their prob-
able appearance during preparation of XXII Olympic
Winter Games of 2014 in Sochi. The risk of mudflows
is especially probable in the Mzymta River Basin.
METHODS AND DATA
As an initial informational data in the assessment
of a mudflow hazard, there were taken the data on mud-
flows in the region under study, information on air tem-
perature and precipitation amounts from the Russian
Hydrometeorological Center and History of alternation
of elementary circulation mechanisms (abbreviated as
ECM) in the atmosphere of the Northern Hemisphere
according to the Classification by B.L. Dzerdzeevskii
(d
zeRdzeevskii
, 1962; k
ononova
, 2010).
CONTENT OF INVESTIGATIONS
The basic characteristics which are used to assess
the hazard of mudflows include intensity of mudflow
process on a given territory, sizes of simultaneously
formed mudflow cones, discharges and velocities of
mudflows and activity of their manifestations. Here,
under activity of a mud-flowing process one under-
stands the frequency of mudflows or duration of a
period between mudflows (UNEP/UNESCO,1988;
n
atuRal
HazaRds
of
R
ussia
, 2002).
Mudflow activity changes in time and is subjected
to cyclic variations of different duration depending on
the factors causing development of mudflows. Just
the activity of mudflows directly depends on weather
ABSTRACT
Assessment of a mudflow hazard in the cur-
rent period of unstable climate and possible extreme
situations is especially important for the Caucasian
Black Sea coast. Here mudflows constantly threaten
to economic and tourist’s objects and happen due to
the mass construction of different structures, includ-
ing their probable appearance during preparation of
XXII Olympic Winter Games of 2014 in Sochi. The
hazard assessment of mudflows is made through ana-
lyzing their activity and the degree to which they af-
fect the territory. Data on the mudflow activity in the
past and present time are extrapolated for the period
up to 2015 basing on analysis of the basic changing
factors of their formation: meteorological and anthro-
pogenic ones in the interaction with geological condi-
tions. High mudflows activity is expected in the near-
est years both on the territory where they were known
earlier and also in the areas under intensive develop-
ment. The highest hazard is possible in 2011 - 2012.
K
ey
words
: mudflow, XXII Olympic winter Games, atmos-
pheric circulation
INTRODUCTION
Assessment of a mudflow hazard in the current pe-
riod of unstable climate and possible extreme situations
is especially important for the Caucasian Black Sea
coast. Here mudflows constantly threaten to economic
and tourist’s objects and happen due to the mass con-
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i.v. mAlNevA & N.K. KoNoNovA
966
5th International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment Padua, Italy - 14-17 June 2011
and Tuapse. Presently data on the number of the
past mudflows are not sufficient as well. In 1970s
the workers from VSEGINGEO have carried out the
engineering-geological investigations of the Black
Sea coast and the adjacent mountainous territory. As
a result of these investigations a special map was
compiled showing the watercourses in the areas of
Novorossiysk and Tuapse and some watercourses in
the highland zone of the Mzymta River Basin as mud-
flow-hazardous ones. Dense forests of the highland
and medium-height zones and small-scaled investiga-
tions (1:200,000) made it impossible to characterize
the mudflow streams of the given territory in more
details, but it was noted that no high intensity of them
was observed. According to the data obtained during
the investigations of the last years, only in the Kra-
snaya Polyana area 40 mudflow-hazardous streams
were registered with 37 among them located in the
Mzymta River basin (mainly from the northern slope
of Aibga Ridge) and 3 streams - in the basin of Psou
River (the southern slope of Aibga Ridge).
It is noted that the most hazardous mudflows are
formed in high mountains and medium-height lands
along watercourses that cut circus moraines or along
channels filled with slide material in the zone of
clayey shale and argillites (streamlet Galion - 2, Vo-
dopadnaya, Tobias, Sulimovsky and others). Due to
steep slopes of channels, the floods in small mudflow-
hazardous basins need little time to reach overflowing
onto flat surfaces and are characterized by sharp rises
and drawdowns of levels and high water discharges.
As it follows from comparison of data of the
investigations, during the recent years the mudflow
hazard on the investigated territory grew, which was
caused, to a considerable degree, by the increased in-
tensity of anthropogenic impacts and in particular by
deforestation and, as a result, the related erosion on
the slopes. Such a tendency is observed generally in
Caucasus during the last decades.
An increase in intensity and activity of the mud-
flow process is considerably connected with the
geological conditions of the given territory and is
observed in the areas composed by metamorphic, ter-
rigenic and flysch rocks of different ages, especially
of Lower- and Middle-Jurassic period. The strength
of clayey and aspid slates, occurred in the upstream of
Mzymta River, highly changes depending on the wet-
ting degree. Of attention is the slight ductility of argil-
extremes, and just this activity represents a hazard of
mudflows in a particular basin or region during the
current epoch (l
in
& l
ee
, 2006; m
a
et alii, 2006;
k
ononova
& m
alneva
, 2007).
At the present time the territory under investiga-
tion is characterized by a slight hazard of mudflows.
Predominantly the mudflows, here, has a capacity of
not more than 10,000 m
3
and a low frequency (once per
15 - 30 years). In the highlands the mudflow frequency
is higher - once per 8 - 15 years. The generating sources
of the most hazardous mudflows are located in the belts
of high and medium-height mountains. The capacity of
mudflows can change from a few tens and hundreds
m
3
to 100,000 m
3
and more. Activity of mudflows is
closely connected with the regime of precipitation.
Depending on the factors that cause formation of
mudflows, the following mudflow-hazardous regions
can be distinguished on the territory under investigation:
Mud-flows that are being formed on small water-
courses and ravines flowing directly into the Black
Sea.
Their activity is especially high in the area of
Novorossiysk City where predominantly water-stony
mudflows are formed due to intensive rainfalls, and
hard fragmental streams considerably - due to dumps
from cement quarries. The slopes are composed of
Upper-Cretaceous flysch and loose sediments of 2-3
m and sometimes to 10 m thick. Mudflows along these
watercourses often damaged railways (in 1946, 1950,
1953 and 1958, as well as in 2009, 2010), causing
interruptions in train traffic, sometimes for 10 days!
In the area stretching from Tuapse to Adler, the mud-
flows are formed mainly in landslide-generating sites.
The character of generating mudflows is usually ero-
sive due to washing-out of accumulated sediments in
stream channels (UNEP/UNESCO, 1988).
Mudflows in high- and medium-height areas of
the Main Caucasian Ridge, which are formed due to
washing-out of loose fragmental rock material com-
ing into the channels of temporary and small water
streams in the form of mud avalanches, slides and de-
bris. In the alpine zone a great role in formation of
hard material flows belongs to ancient moraine.
Until 1950s of ХХ century recoding of mudflow
manifestations in the above-mentioned regions actu-
ally was not fulfilled with the exception of the most
hazardous territories, i.e. the cities of Novorossiysk
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ASSESSMENT OF A MUDFLOW HAZARD ON THE BLACK SEA COAST OF CAUCASUS
AND IN THE ADJACENT MOUNTAINOUS AREAS
Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
967
indeed, sufficiently high. However in July in the
same area the rainfall has also been heavy (Novo-
rosiysk, 23 July - 42.4 mm, 24 July - 89.9 mm), but
no information was about floods and mudflows. The
first significant manifestation of mudflows happened
on August 6, the next rains fell on the territory when
it was already prepared for activation of exogenic
processes by the weather of the previous period,
therefore they caused mass mudflows and activation
of landslides in the surface sediments.
It is known that in the north-western part of the
Black Sea coast the most mudflow-hazardous in the
sliding and erosive-sliding sites were the years with an
increased humidity - 1960, 1962, 1967, 1970, etc. In
these years the meteorological stations of Anapa and
Novorossiysk recorded an increase of days with heavy
rainfalls. In the area of Tuapse and Novorossiysk the
daily precipitation amount exceeded 100 mm in all
the cases of mudflows. As we have established, in this
part of Caucasus the daily maximum precipitation is
highest in those years when the monthly and annual
precipitation amounts considerably exceed the long-
term period average precipitation sums.
It should be noted that the multi-year course of
the annual precipitation on the Black Sea coast and in
the adjacent territory of North Caucasus (Sochi, Kras-
naya Polyana) differs slightly. The multi-year courses
of precipitation in seasons of the year at some mete-
orological stations have generally also much common.
In the multi-year course of annual precipitation
amounts there are seen the extreme years when pre-
cipitation much exceeds the norm (1924, 1932, 1937,
1939, 1940, 1953, 1955, 1958, 1967, 1977, 1988-1989,
2002). The territory under investigation is character-
lites, clayey shale, aleurolites to weathering processes,
especially in areas of tectonic crushing. In many cases
rocks are soaked and swollen or become even flu-
ent. On clayey shale such a zone with highly soaking
heavy loams with inclusion of rock debris can have a
thickness of 1 to 5 m. Typical to such rocks is a de-
crease in resistance to shearing and development of a
sliding process, including in sites of originating mud-
flows. Simultaneously with this is lower resistance to
erosive wash-out. It is natural that in the zone of the
Lower-Jurassic, Eocene-Oligocene clayey rocks that
are low-stable to denudation, and loamy slope forma-
tions of different genesis, there are formed mud-stony
streams different by thickness and density.
Investigations of the conditions of forming mud-
flows on the Black Sea coast of Caucasus and in the
adjacent mountainous areas have established that the
basic factor increasing their activity is the degree and
regime of territory wetting.
Analysis of all the known cases of mudflow for-
mation makes it possible to note that a close linkage
exists between precipitation and mudflows in the given
region, especially in lowlands. Thus, in the area of Tu-
apse and Novorossiysk the daily precipitation amount
during mudflows exceeds, as a rule, 100 mm. Sources
of hard stony streams here are small-sized landslides,
detrital cones of ravines, covers of alluvial sediments
at slope foots, as well as sediments from the channels
washed out by floor erosion. The high mudflow hazard
of the Tuapse region is evidenced by the sad events oc-
curred in the beginning of August 1991, which covered
the mountains and the coast in the area of Tuapse-So-
chi and distributed over the northern macro-slope up to
Maikop City. At night from July 31 to August 1 a heavy
rainfall happened in these areas. The rainfall caused a
high water in the rivers and activated mudflows. The
similar tragedy occurred here in October 2010.
In the area of Novorossiysk the catastrophic mani-
festation of mudflows in August 2002 was also caused
by anomalous precipitation. The center of catastrophic
events was in the area of Novorossiysk City. Heavy
rains covered the entire Krasnodar Region and caused
mud streams. The precipitation amounts in those days
are presented in Table 1.
Thus, on some days (5 and 8 August in Novorossi-
ysk and August 6-8 in Anapa) daily precipitation sums
exceeded the long-term monthly average sum.
The above-indicated precipitation amounts are,
Tab. 1 - Daily precipitation sums in August 2002
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i.v. mAlNevA & N.K. KoNoNovA
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5th International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment Padua, Italy - 14-17 June 2011
ity of slopes occurs. Here, mudflows are connected,
first of all, with those macro-circulation processes, at
which the probability of rainfalls is not less than 60%,
and with those which bring intensive precipitation
with a 10% provision, most often - heavy rains.
It is established that the most dangerous weather
for any sites of mudflow origination on the given ter-
ritory is connected with those ECM-mechanisms, at
which the Mediterranean cyclones outcrop to the Black
Sea coast of Caucasus. The unstable weather, brought
by these ECM, form favorable conditions for alternate
wetting-drying of easily breakable rocks in mudflow-
generating sites and accumulation of loose detrital rock
materials; intensive rainfalls cause run-off of crushed
rock materials and formation of liquid mudflows. For
the basin of Mzymta River and the adjacent areas of the
Krasnodar Region the same ECMs are dangerous. The
dynamic schemes of them are shown in Figg.1 and 2.
As activation of mudflows needs abundant rain-
falls, then through analyzing the linkage of daily pre-
cipitation sums, recorded at meteorological stations of
Sochi, Krasnaya Polyana, Novorossiysk and Tuapse,
with the elementary circulation mechanisms, those
ECMs were distinguished, at which precipitation
falls out not less than in 60% of cases of manifest-
ing the given ECM and amounts in total to not less
than 50% of the monthly precipitation in a concrete
month. These turned out to be ECMs 12a and 13 s. It
can be seen from the schemes of Figures. 1 and 2 that
at these mechanisms North Caucasus expects coming
ized by a high homogeneity of the multi-year regime
of precipitation. This is confirmed by the high correla-
tion coefficients between the rows of annual precipi-
tation at different meteorological points. These coeffi-
cients are equal to: Achishkho-Krasnaya Polyana-0.89;
Achishkho-Goitkh-0.76; Sochi-Krasnaya Polyana-
0.89. However, according to the values of heat- and
moisture provision, the regime of meteorological fac-
tors, which determine activity of exogenic geological
processes, in highlands and medium-height areas will
significantly differ from those located on the coast and
in the piedmont areas both between years with extreme
precipitation values and by the sum of precipitation.
Formation of mudflows on the investigated terri-
tory depends not only on absolute values of air tem-
perature and precipitation amount, but also on the
character of weather in general which can be quan-
titatively expressed by a number of days with one
or other macro-circulation processes in the Northern
Hemisphere (d
zeRdzeevskii
, 1962).
For analysis of circulation conditions it is reason-
able to use the Classification of elementary circulation
mechanisms (abbreviated as ECM) of the Northern
Hemisphere, developed by B.L. Dzerdzeevskii jointly
with his. graduates The information on the Classifi-
cation can be found on the website www.atmospher-
ic-circulation.ru
. The entire variety of circulation
processes on the Hemisphere is represented in this
Classification by 41 elementary circulation mecha-
nisms (ECM). For each ECM a scheme of cyclones
movement and stationing of anticyclones is given pro-
viding the possibility to imagine vividly a manifesta-
tion of each ECM in any region of the Hemisphere.
The History of alternation of ECM is compiled
since 1899 till the present time, where for each day the
appropriate ECM is indicated. By means of compar-
ing the time of mudflow activation with the Calendar
of ECM alternation it was determined at which ECM
that kind of weather is formed which causes activation
of mudflows in different sites of their origination.
In the erosion sites, these are the ECM that cause
intensive destruction of rocks due to frequent changes
of their wetting state into drying and freezing into
thawing, as well as intensive run-off of weathering
products and wash-out of channel sediments.
In the sliding sites for the formation of mudflows,
of importance are amounts of precipitation and such
a regime of its fall-out, at which destruction of stabil-
Fig. 1 - Dynamic scheme of ECM 12a:. Letters ‘H’ and ‘L’
denote correspondingly high atmosphere pressure
(anticyclone) and low one (cyclone)
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ASSESSMENT OF A MUDFLOW HAZARD ON THE BLACK SEA COAST OF CAUCASUS
AND IN THE ADJACENT MOUNTAINOUS AREAS
Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
969
is casual. Implementation of this model by means of the
program MAPR makes it possible to fulfill extrapola-
tion for the fourth part of the time row. Accuracy of the
predictive assessment with 60%-provision is within the
standard deviation, with 90%-provision is within twice
standard deviation.
Using the above-mentioned program and with the
aid of statistical criteria one finds a trend and cycles
in the time rows, determines parameters of the func-
tions which describe regular changes; and as a result,
by regular and casual components of the initial time
row the predictive values are produced.
The obtained results give the possibility to com-
pare the time rows of different mudflow-forming fac-
tors. The degree of mudflow activity in concrete years
depends on the force with which the factors influence
the mudflow process. The activity is considered strong
when mudflows cover over 60% of mudflow streams
within a territory under study; medium activity - when
mudflows cover 30 to 60% of streams, and weak -
when less than 30% of territory.
On the basis of extrapolation of the basic chang-
of Mediterranean cyclones.
The total annual duration of these ECM (Figure.
3) according to the data of 2009 significantly exceeds
the average one for 1899 - 2009. The tendency of last
changes shows a curve 3 (10-year smoothing). It is
seen that the total annual duration of precipitation
forming ECM for the Black Sea coast in the modern
period is the highest of all time since 1899. This gives
the grounds to suppose that in the nearest 10 - 15 years
the risk of mudflows in this region will remain high.
The above-described statements allow us to pass
to the assessment of mudflow activity using the data
of the above-indicated fast-changing factors caus-
ing the development of mudflows. Here, it should
be noted that assessment of mudflow activity for
the nearest decade on the regional level represents
only the assessment of probability of appearance of a
mudflow-hazardous situation. The given assessment
requires yearly specification.
For all the factors determining the activity of
mudflows in the given region the time rows are com-
piled. Analysis of the time rows gives the possibility
with sufficient substantiation to predict the degree of
mudflow-hazardous situations in the zones of low-
height mountains, medium-height and high mountains
of the territory under investigation. Knowledge of the
cyclic character of mudflows helps the mathematical
model’s extrapolation process:
x(t) = η(t) + z(t) + e(t)
where the components η(е) and z(t) are regular, and e(t)
Fig. 2 - Dynamic scheme of ECM 13s:. Letters ‘H’ and ‘L’
denote correspondingly high atmosphere pressure
(anticyclone) and low one (cyclone)
Fig. 3 - Total annual duration of ECM 12a and 13s. 1 - an-
nual duration, 2 - average for 1899 - 2009, 3 - an-
nual duration smoothed by a sliding 10-years
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i.v. mAlNevA & N.K. KoNoNovA
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5th International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment Padua, Italy - 14-17 June 2011
ing factors of mudflow formation in the Mzymta River
basin and the adjacent territory of the Krasnodar Re-
gion it is possible to assess the mudflow-hazardous situ-
ation for the nearest ten years. Thus, in the nearest years
the amount of precipitation on the Caucasian Black
Sea coast and in the adjacent mountainous areas will
remain sufficiently high, especially in the area of low
mountains. A considerable increase in precipitation is
possible in 2012. In this year the precipitation increase
is expected in January and February, which may lead to
development of a sliding process in this area and, hence,
to activation of mudflow origination. In summer when
heavy rainfalls are possible at ECM 13s, an increase of
precipitation is also possible in 2012. The above-pro-
posed high duration of ECM 12a in spring and 13s in
summer and extreme character of weather at these ECM
confirm the truth of the statistical predictions.
Prediction of mudflows for this region was made
first in 1975. Increase in mudflow activity was expected
in the years of 1981-1982, 1987-1988 and 1992-1993.
The prediction proved to be correct. The proposed high
activity of mudflows in 2002 proved also to be correct.
The natural conditions of mudflow formation on
the territory under study are considerably disturbed
by anthropogenic activities, the intensity of which is
presently increasing fast. All this considerably affects
the geological environment. Many types of economic
development of the territory cause watering of soils,
a rise of shallow groundwater level, soaking of rocks
and decrease of their strength properties, which on
the given territory are not so high, as it was shown
above. When the natural and anthropogenic factors act
jointly, the hazard of mudflows in the above-discussed
rock complexes will be especially high.
Taking into account the construction of Olympic
objects, activity of formation of stony streams will
considerably increase and, with anomalous wetting,
can lead to formation of mudflows with a capacity of
to 200,000 m
3
.
The hazard of mudflow formation is explained by
the fact that even small mudflows formed, for example,
in water streams on the slope of Aibga Ridge and so on,
can be added with active landslides developed on the
left- and right-hand shores of Mzymta River. As a result,
Mzymta can be dammed by the formed catastrophic
mudflow. Therefore, a special attention should be given
to assessment of the present-day activity of landslides of
different genetic types, and to their possible manifesta-
tions as sources of a hard component of mudflows.
Attention should be paid also to other areas with a
high intensity of landslides in the basin of Mzymta Riv-
er, with which manifestations of large-sized mudflows
can be connected, in particular, the basin of Medoveev-
ka River. Also, a very dangerous area is the basin of
Kepshi River, characterized by an extremely high risk
of mudflows. There are known mudflows here, which
are connected with landslide-originating sites. With ac-
tivation of a landslide, formation of a catastrophic mud
flow of a capacity of to 300,000 m
3
is possible.
CONCLUSIONS
1. In the nearest years one should expect a high in-
crease of mudflow hazard on the Black Sea coast
and in the adjacent mountainous areas due to in-
creasing intensity and activity of mudflow process
as a result of natural and anthropogenic factors.
2. According to analysis of the conditions for de-
velopment of mudflows and factors that cause
them, the next increase of mudflow activity is
expected in 2011-2012.
3. With a considerable increase in mudflow hazard,
the mudflows in the given area can be formed in
places where they never happened. The expected
increasing anthropogenic load connected with the
Olympic Games of 2014, the total impact of na-
tural and anthropogenic factors can be especially
high. Many economic objects can be damaged
even by small mudflows. Thus, for some certain
objects, for example, oil- and gas pipelines, high-
ways even the mudflows of low capacity will be
dangerous. They can interrupt the traffic for a long
time and cause a large material damage.
4. To prevent possible catastrophic events is impos-
sible, but negative consequences of them can be
minimized to conduct systematic monitoring of
hazardous exogenic geological processes.
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ononova
N.K. (2001) - Long-term fluctuations of Northern Hemisphere atmospheric circulation according to Dzerdzeevskii’s
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ASSESSMENT OF A MUDFLOW HAZARD ON THE BLACK SEA COAST OF CAUCASUS
AND IN THE ADJACENT MOUNTAINOUS AREAS
Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
971
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Statistics