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years is about 0.5 m/year, and the maximal rate is up to 2 m/year (Ryabchuk et al.
2007 ) . The maximal distance of shoreline retreat is observed in the vicinity of the
town of Zelenogorsk (former Terijoki), where, according to the analysis of old maps
and remote sensing data, the coast retreated landward at a distance of about 100 m
in the course of a century (Ryabchuk et al. 2009 ) .
16.5.2.2 Sea Bottom Erosion and Sediment Flows
Many important features of coastal dynamics are caused by nearshore processes.
The eastern Gulf of Finland, for example, can be attributed as a wave- and storm-
dominated shallow clastic sea (Reading 1996 ) . According to Reading ( 1996 ) , the
main controls on sediment transport in such a case are (i) the frequency and inten-
sity of storm-induced currents; (ii) nature and origin of sediment supply; and (iii)
sea-level fluctuation. The important feature of the hydraulic regime of the nontidal
Gulf of Finland is the nonperiodic sea-level change. The most significant sea-level
variations in the eastern Gulf of Finland apparently occur as a result of combined
effect of wind-induced storm surge and progressive long waves caused by cyclones
moving along the Baltic Sea and the Gulf of Finland (Eremina et al. 1999 ) . The
minimal value of the sea level (-1.24 m) was registered on November 2, 1910,
and the highest surge (4.21 m) occurred on November 19, 1824. About 307 floods
higher than 160 cm are documented in the history of St. Petersburg during the
period from 1703 to 2008. Eighty-nine percent of surges were caused by west-
ern and southwestern cyclones (Pomeranets 2005 ) . The interaction of waves and
storm-induced currents with sea-level fluctuation can be the reason for the forma-
tion of bedforms, typical for tidal seas, i.e., sand ridges, sand waves, and erosional
streams.
The most significant erosion is observed within autochthonous coastal systems
(Reading 1996 ) with minor outer sediment supply, such as the northern coast of
the Gulf of Finland between capes Peschany and Dubovskoy. During fair-weather
hydraulic conditions, the nearshore surface is characterized by dynamic equilibrium;
storm surges break the balance and generate offshore sediment flows.
Configuration of the shoreline and dominated winds from the west and southwest
resulted in sediment transport along the coast in the eastern direction (Fig. 16.8a ) .
Therefore, sediment flux along the northern coast tends to decay in this direction.
In the vicinity of Zelenogorsk, sediment flux is close to 30,000 m 3 /m/year (cubic
meters per meter if shoreline per year), while near the town of Repino, sediment flux
is 20,000 m 3 /m/year and in the vicinity of Solnechnoye, it is almost zero (Leont'yev
2008 ) .
The eastern sediment transport along the coast discharges in front of Sestroretsk.
It has changed due to coastline variations (Figs. 16.7 and 16.8a ) . As a result, accre-
tion of beach sands up to 140 m wide is observed here. In the nearshore zone, there
is sand accretion as well, showing a very shallow submarine terrace surface with a
system of sandbars and furrows composed of fine-grained, well-sorted sands. But
retrospective analyses of remote sensing data have shown that the shoreline has not
aggraded here. The main reason for this phenomenon is the slope gradient (depth
increase from 2 to 5 m along the distance of 100 m) of the sand terrace which
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