10 research outputs found
Causes and systematics of inundations of the Krasnodar territory on the Russian Black Sea coast
The inundation situations on the Black Sea coast of the Krasnodar
territory for the period from 1945 until 2013 were analysed and the main
types of inundations at the coast are described. Synoptic factors of the
formation of extreme precipitation and rainfall floods, features and regularities
of the downstream flood wave transformation in the rivers are also studied.
Therefore, assessments of seasonal and maximum flow of the Black Sea coast
rivers for the period of hydrometric measurements were done. Regularities of
change of the occurrence of inundations and their characteristics on the
coastal terrain were analysed, for a year and on a perennial timescale.
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Most catastrophic and exceptional inundations arise in the summer and in
early autumn. Small inundations during the remaining year reflect the
seasonal distribution of river flow and floods in the Black Sea rivers.
Extensive and sometimes extreme precipitation dominates the river flow
regimes. The seasonal distribution of small and moderately dangerous
inundations reflects, on average, a water regime of two groups of rivers of
the coast – to the north and to the south of the Tuapse River. To the north
of the Tuapse River, floods prevail from November until March (up to 70 %
of observed floods took place in this period)
as a result of precipitation and winter snowmelt during frequent thaw
periods. In winter, high waters often overlap to form a multi-peak high water
of 2–3 weeks' duration. In the summer and in early autumn we observe a steady
low flow. The total amount of runoff increases both in a southeast direction,
and with the altitude of the river basins. Interannual variability of mean
annual runoff, as well as maximum runoff, on the contrary decreases in the
southern direction and with an increasing area of the river basins. The coastal
high waters of the rivers of the Sochi part of the coast are typical at any time of the
year, but more often floods in the cold season result from incessant rain,
and thawing snow. Annually up to 25 floods have been observed. The principal
reason of such distribution is the increase of extreme rainfall in the warm
season.
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Orographic features of the coast and detailed features of rainfall only cover
a small number of local river basins and a limited area. The geographical
correlation of individual rainfall and subsequent floods ceases to be
statistically significant for distances over 40–60 km.
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The annual flow cycle is mainly determined by two seasons, winter/spring and
summer, with strong and weak flows, respectively; almost 71 % of all
catastrophic and exceptional inundations took place in July–August
(71 %) and in October–November (29 %). The characteristic features
of dangerous floods are their rapid formation and propagation, a significant
increase of water level (up to 5–7 m and more) and the multiple increase of
water discharges in comparison with low flow period.
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Analysis of the interannual changes of the number of inundations at the
Black Sea coast of the Krasnodar territory has shown some increase of the number
of inundations in the period from the early 1970s until the early years of
the twenty-first century.
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Quantitative assessments of risk, hazard and damage for the population and
economic activities from accidental inundations in the valleys of the Black
Sea coast rivers show that economic and social losses from inundations at
the Black Sea coast of the Krasnodar territory are some of the highest in the
Russian Federation. The basic conclusion from recent inundations is the need
to consider not only the lower reaches and mouths of the Black Sea coast
rivers where the main part of the social and economic development of the
coast is concentrated, but also whole river basins and catchments. Further,
an analysis of the efficiency of the measures applied at the coast to
mitigate inundations and their after-effects is provided