Introduction

An intensification of the coastal processes has been observed over the last few decades all over the world coasts (Bird 1985).

In the Russian Federation 25 000 km of the 61 000 km total length of the marine coast suffers from severe erosion. The most heavily eroded are the coasts of the White Sea, Sakhalin Island, the Kamchatka Peninsula, the Kaliningrad District, the Black Sea and the Azov Sea (Luk'yanova et al. 2002).

In the Russian Arctic the eroded coasts amount to 38% of the total shoreline length (Kalinina et. al. 1992). On coasts composed of easily eroded Quaternary deposits (the Laptev Sea, the East Siberian Sea, the northern coast of Yamal Peninsula in the Kara Sea) the rate of shoreline retreat reaches 3–12 m/year as a result of thermal erosion (Kaplin et al. 1991; Aibulatov 2005). In the Far East (the Bering Sea, the Sea of Okhotsk, the Sea of Japan) about 50% (about 4000 km) of coasts suffer from erosion (Kalinina et. al. 1992; Aibulatov 2005). The coasts of the southern seas, the Black Sea and the Azov Sea, are the most valuable recreational coasts for the Russian Federation. The geological structure and geomorphology of the Russian sector of the Black Sea can be subdivided into two areas. The coastal areas of the Taman Peninsula consist of plains and gently sloping hills up to 130 m high, while in the region of the Caucasus, marl, limestones, argillites and sandstone flysch form mountain slopes adjacent to the shoreline (Aibulatov 2005). 309 of the 400 km Black Sea coast of Russia is characterized by erosion and landslides (Kos’yan et al. 2005). Erosion processes are a consequence of anthropogenic impact. Until the end of XIX century the average width of beaches was 46 m and the coastal zone was stable. Removal of beach material, construction of harbours and coastal protection structures caused drastic degradation of the coasts (Kos'yan and Kuklev 2008). The coastline of the Azov Sea is 572 km, of which 227 km is eroded. Erosion and landslides are observed along 47% of northern coast and 55% of southern coast of Taganrog Bay (Luk'yanova et al. 2002). The Russian coast of the Caspian Sea (1460 km long) can be divided into deltaic sections (Volga River delta) formed from sand and shell detritus, sand accretion spits and the straight coast of Dagestan (Leont’ev 1955). Recently, due to a rise of sea-level (2 m during last 25 years), very high shoreline retreat, with yearly loss of about 2000 hectares of land, is observed (Luk'yanova et al. 2002).

The problem of coastal erosion is very topical for the people of the coast of the Russian Baltic within Kaliningrad District. Along the open the Baltic Sea coast of the Kaliningrad area the erosion processes are extremely active. The average rate of recession of the cliff coasts of the Sambian Peninsula is 0,5 to 0,7 m per year. Some significant sections of the Vistula and especially the Curonian spit coasts, both on the seaward and lagoon sides, are actively eroded. The most serious impact for the unique landscapes of the Curonian Spit National Park, as well as for the fresh-water environment of the Curonian Lagoon, is spit breaching during extreme storm events. The Curonian Spit is known to have “weak points” where storm waves can break through the sand body. Between 1988 and 1996 the seaward coast was threatened six times by extreme storms. During these storm events, the shoreline retreated 8–10 m along the distal part of the spit and 2–3 m close to Lesnoy village. In 1983, as a result of a storm event, the spit was breached along 50–60 m of the coastline near Lesnoy (Boldyrev et al. 1990).

The problem is very important for many Baltic countries (Workshop on Sea-Level Rise and Climate Change 2008). Along Latvia’s open Baltic seacoast during last 50–60 years the recession exceeded 50–60 m (up to 200 m). Coastal erosion is less along coast of the Gulf of Riga. During the last 15 years, coastal erosion has significantly increased due to severe storms (Eberhards et al. 2009). In Lithuania the total annual sand sediment budget of the coastal zone is negative with a loss of around 13000 m3. The length of accumulating sectors of Lithuanian coast between 1993- and 2003 has decreased from 36 to 20.3 km, and the length of eroded and stable coastal sectors has increased by 1.5 times (from 16 to 24.2 km and from 37.5 to 54.7 km respectively) (Bitinas et al. 2005). In Poland three types of coast are distinguished: cliffs (101 km), barriers (380 km) and wetland coasts (salt marshes) (17 km). Cliff coasts suffer from mass movements, and there are serious risks related to erosion of low and narrow barriers, which could be easily broken during storm surges (Uscinowicz et al. 2004). An increase in the intensity of coastal processes has been observed in Estonia during the last 20–30 years in spite of isostatic and neotectonic uplift (Orviku et al. 2003). On the contrary, the northern coast of the Gulf of Finland is stable due to the geological structure (solid crystalline and metamorphic rocks) and tectonic uplift.

Traditionally the coastal zone of the easternmost (Russian) part of the Gulf of Finland has not been considered as an area of active litho- and morphodynamics, but our study has shown that within some coastal segments shoreline the recession rate reaches 2 – 2.5 m/year (Ryabchuk et al., 2009a). The main objectives of this paper are to evaluate the current state of the coastal zone and to identify the areas which most suffer from erosion. Another objective is to analyze recent trends with respect to the coastal dynamics and establish the geological and geomorphic reasons behind the observed processes.

Materials and methods

The Department of Marine and Environmental Geology of the A.P.Karpinsky Russian Research Geological Institute (VSEGEI) has been undertaking sea-bed mapping, geological and environmental geological investigations in the eastern Gulf of Finland since 1980 (Moskalenko et al. 2004; Spiridonov et al. 1988; Spiridonov et al. 2007). During the last decade many projects studied the coastal dynamics.

Between 2005 and 2008 VSEGEI undertook multipurpose research as a part of the project “Up-to-date assessment of mineral-resource potential, control over geological hazards and the development of a prediction model for the geological environment of the Baltic Sea and its coastal zone” funded by the Federal Agency on Mineral Resources of Russian Federation. One of the objectives of the project was to create a model of the Coastal zone Cadastre (Zhamoida et al. 2008). Field observations were carried out along the entire length of the coast of the Russian part of the Gulf of Finland and zones of intense coastal change were documented. Some of coastal segments which suffer most from erosion were selected as key areas for detailed investigation.

Within the key areas, on-land investigations and near-shore studies were undertaken. Repeated onshore observations included a detailed description and mapping of the coast (measuring beach width, photographing specific features, describing the sediments composition, sediment sampling for grain-size analyses, estimation of foredune condition). Field observations were considered alongside remote sensing data (aerial photos of 1990, resolution 0,5 m; Quick Bird space pictures of 2005, resolution 0,64 m) and charts published in the 19th and 20th centuries. Retrospective analysis of old charts and remote sensing data allowed the areas of shoreline recession and advance as well as stable coastal segments to be established and the calculation of the average rate of erosion/accretion.

Shallow water areas of the near-shore zone were studied using side-scan sonar profiling (CM2, C-MAX Ltd, UK) with a search swath of 100 m using a working acoustic frequency of 324 kHz. Within the northern coastal zone of the Kurortny District, 900 km of side-scan profiling (including 400 km of repeated survey) perpendicular to the shoreline were undertaken between 2005 and 2009. Along the southern coast 75 km of side-scan survey were carried out. The distance between profiles (186 m) gave a continuous acoustic picture of the sea bottom, allowing the study of the distribution of surface sediment types. Side-scan profiling was accompanied by echo-sounding. Repeated survey of some parts of near-shore zone and key profiles showed changes to the bottom relief based on 3D images and gave information on the sediment dynamics.

The interpretation of sonar data was confirmed by sediment sampling and under-water video observations using a video-ROV Fish106M (Intershelf, St.Petersburg, Russia). Sediment sampling (232 samples) along the side-scan sonar profiles was undertaken using a grab-sampler and a small drag-sampler. Sediment sampling on the coastal slope, from coast line to a water depth about 2.5 m was undertaken by divers.

Results of the coastal zone study

The analysis of remote sensing data and results of field observations show that erosion process differs in different parts of coastal zone.

From the geological point of view, the investigated coastal zone has features that result primarily from its location at the boundary between the Baltic Shield and Russian Platform. Geological processes resulting from the last glaciation and the alteration of continental, lacustrine and marine environments over the last 14 500 years have played an important role in the formation of the relief and the sediment distribution (Spiridonov at al., 2007). The final stage of development took place 2–2.5 thousand years ago when Ladoga Lake waters burst out to the Baltic Sea with formation of the Neva River.

Both the shore and nearshore zone are totally covered by Quaternary deposits up to 20–40 m thick. Bedrock, (rapakivi-granites), locally outcrops just to the west of Vyborg Bay. The Quaternary deposits are comprised of glacial till, lacustrine-glacial deposits of local ice lakes and the Baltic Ice Lake, and Holocene (Ancylus Lake, Litorina and Limnea marine) sand and clays (Geoecological atlas… 2002). Quaternary sands and clays are very easily eroded. As a result of glacial till erosion a bounder-pebble bench is forming and of there is a sediment deficit (caused by sediment starvation) (Ryabchuk et al. 2009a).

Some parts of the eastern Gulf of Finland coastal zone, such as the granite and glacial till skerries of the northern coast (between Primorsk town and Russian-Finnish border) and the large bays (Luga Bay, Koporsky Bay) of the southern coast, are rather stable (Fig. 1). The most valuable areas from recreational, economical and social points of view, such as the northern coastal zone of Kurortny (meaning “Resort”) District, the northern coast of Neva Bay and part of southern coast between Lebyazhye village and the St.Petersburg Flood Protection Facility (Fig. 1), are situated among the most heavily eroded coastal segments.

Fig. 1
figure 1

Map of investigated area. Key areas: 1—coastal zone of Kurortny District; 2—southern coastal zone near Lebyazhye village

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The Kurortny District coastal zone

The Kurortny District of St.Petersburg is located along the northern coast of the Gulf of Finland to the west of St.Petersburg Flood Protection Facility (Fig. 1). It has special importance as a unique recreational area of the North-West Region of Russia. Sandy beaches and a comfortable climate resulted in the building of many sanatoriums, hotels and entertainment centers. Some areas (for example Zelenogorsk town, the former Terijoki, Komarovo village, the former Kuokkala, Solnechnoye village, the former Olila) have been used as fashionable resorts since the second half of 19th century. Two Nature Reserves (a sandy beach with dunes in Komarovo village and oak park “Dubki” founded by tsar Peter I) are located in this area.

Coastal erosion is a serious problem in the area. The analysis of historical materials, archive aerial photographs and modern high-resolution satellite images have shown that there are practically no sections of advancing coast—with most of the coast being eroded and retreating. The remote sensing data analysis shows that the average rate of shoreline retreat from 1990 to 2005 was 0.5 m/year, while the maximum rates reached 2 to 2.2 m/year. The maximum landward shift of the shoreline for this period of time is 35–39 m. Local areas of sand accretion and shoreline shift seaward are observed near the mouths of small rivers. Segments of boulder coast are usually stable, as is the sandy beach in the vicinity of Sestroretsk town (Ryabchuk et al., 2007). The field work monitoring observations (2004–2007) showed intense damage of sandy beaches during autumn and winter storms and the progressive erosion of dunes system (Fig. 2).

Fig. 2
figure 2

Erosion of the foredune after autumn and winter storms accompanied by sea-level rise (Komarovo Nature Reserve)

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The erosion problem is made worse by anthropogenic impacts, an old ineffective system of coast protection (Fig. 3) and intense and reaped development of recreational infrastructure.

Fig. 3
figure 3

Coastal protection structures in disrepair in the Kurort District of St.Petersburg

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The strategy for coastal protection has not changed since the beginning of 20th century. Total length of the shoreline within Kurortny District is about 40 km. About 15 km is boulder coast which was formed as a result of glacial till erosion. Along this type of coast 8 km is protected by groins perpendicular to the coast line and about 2 km is strengthened by sea-walls. Both types of construction are ineffective due to a sediment deficit and intense wave impact. They do not protect the shore and need constant repair. The impact of large hydrotechnical constructions such as quays and jetties that serve as groins stopping the littoral drift is more serious. For example, a 90 m long jetty was constructed in 1911 perpendicular to the beach of Zelenogorsk town. Analysis of old charts from the end of 19th century to the first half of 20th century and remote sensing data (1959, 1990, 2006) show the shoreline east to the jetty retreated up to 100 m between 1909–2006 (Ryabchuk et al. 2009a).

Sandy coasts amount to about 23 km and two thirds of them are significantly eroded. In 1988, attempts were made to nourish the beaches. Along a 430 m long section of the coast at Komarovo an artificial beach 50 m wide and 2 m high was created, with the total sand volume of 32250 m3. This artificial beach was an experimental type of the coastal protection, which was evidently successful as it prevented even larger shore damage for two decades. Today, the artificial beach is completely washed away (Ryabchuk et al., 2009a).

Recent development of recreational infrastructure (such as restaurants, entertaining centers, yacht-clubs etc.) caused an acceleration of erosion processes. Without an integrated strategy of coastal zone management and coastal protection, proprietors of recreational facilities try to protect segments of the shore using different approaches. Such activities may solve the problem in some areas, but in others, the state of adjacent coastal area is degraded.

Intense erosion may be entirely natural. The coastline of the area is open to storm waves resulting from westerly and south-westerly winds which are frequent and strong in the study area. The sediments of the coastal zone, as discussed above, are easily eroded Quaternary deposits. The northern coast of the Gulf of Finland within the Kurortny District is located in an area of differentiated vertical tectonic movements, with prevailing uplift. The rate of modern tectonic movements is close to 0 near Zelenogorsk. To the west it increases to +1,5 mm/year and to the east it decreases to −2,5 mm/year (Yaduta 2002).

The nearshore bottom investigation showed some morphological and litho-dynamic features important with respect to the coastal processes. Firstly, an easterly alongshore sediment flow deposits sediment in front of Sestroretsk due to a change in coastal orientation coastal line extend changing. As a result there is sand accretion of up to 140 m on the beach. In the nearshore zone a very shallow submarine terrace surface with a system of sand bars and runnels composed by fine-grained well sorted sands is developing. However an analysis of remote sensing data has shown that the shoreline is not advancing. The main reason for this is the steep slope (depth increase from 2 to 5 m over 100 m) of a narrow sand accretion terrace about 500 m from the shoreline, leading to significant sand accumulation at the foot of the terrace.

An alongshore submarine terrace is very narrow in eastern part of investigated area but becomes 2–2.5 km wide on the northern coast near Komarovo village. The terrace surface is at the depth of 4–5 m, and is base is at a depth of 8–12 m. There are sand ridges on the terrace surface at an angle of about 450 to the coastline (Fig. 4). Repeated profiling of the submarine terrace located between Cape Peschany and Repino village and comparison with old nautical charts shows the progressive erosion of the marine edge of the terrace. While a terrace with the surface at the depth 3–5 m exists, some erosion protection is provided to the coast. Erosion of the terrace is therefore a problem, with coastal erosion being correlated with the state of the submarine terrace.

Fig. 4
figure 4

3D-diagram of the submarine terrace in front of northern coast of the Gulf of Finland

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Near the base of the terrace there are interesting bottom relief forms. Canyon-like erosion runnels (up to 30–50 cm deep) have been observed at a depth 8 to 12 m (Ryabchuk et al. 2007). Repeated survey has shown that these forms are very stable in spite of their relatively shallow depths. Erosion runnels were found all along the coast in a westerly direction between Cape Peschany and Repino village. The bottom of the erosion runnels is characterized by very distinct ripples (up to 20 cm high) composed of coarse-grained sand. The ripples are perpendicularly orientated to the runnel direction. The distance between ripples crests varies from 40 cm to 1 m (Fig. 5).

Fig. 5
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Side-scan sonar images of erosion runnels

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The southern coastal zone

The southern coastal zone between Lebyazhye village and the St.Petersburg Flood Protection Facility (Fig. 1) is less developed as a recreational area. Nevertheless sand beaches located in the vicinity of St.-Petersburg are likely to see future development. The study area is also very important for nature protection as the "Lebiazhii" Sanctuary (a RAMSAR Site for migrating bird feeding in spring and autumn) is located here.

The southern coastal zone can be subdivided into three types—erosion, sand accumulative and artificial. Near Bolshaya Izhora village there is an area of long-term sand accretion with a complex sandy spit system consisting of “hooked spits” of different form, size and age, a feature unique in the eastern Gulf of Finland. The distance between the shoreline, which was formed before the spit development began, and the modern shoreline is about 500 m. There are elongated shallow water lagoons between the spits. The marine coast of the spit to the east of Tchernaya River is actively eroded. Under the eroded spit is an outcrop of organic rich silty-clay. In 2008, sediment sampling of the relict lagoon mud was undertaken using a post-hole digger. 14C-dating of relict silty-clay mud from the shoreline (0–20 cm under the modern sandy spit) has an age 1800 ± 170 BP (calibrated years). A 1 to 1.5 m thick relict sand spit is located 100 m landward from the modern shoreline. 14C-dating of the organic rich sandy-clay layer from 1.3–1.5 m depth is 2060 ± 150 BP. Sand accretion and spit growth has therefore taken place at least over the last two thousand years (Ryabchuk et al. 2009b).

Coastal zone dynamics in this area are very active. Many observations (Geology of the Gulf of Finland 1992) during the 1970s and 1980s in the area of Lebyazhye and Bolshaya Izhora show that the processes resulting in coastal erosion have become more intense. The analysis of aerial photos of sandy beaches to the west of Lebyazhye from 1975–1976 to 1989–1990 show that they were eroded by up to 70 m near Bolshaya Izora and up to 70 m at the coastline extent of 200–300 m.

One of the most important purposes of this study was the detailed analysis of the changing coastal dynamics to establish both mesoscale (decadal) and small scale (seasonal) alterations.

The comparison of coastline GPS surveys with nautical and topographic charts published in the 1980s shows considerable change over the period. The configuration of sand bodies has changes since 1982 with the eastern part of the sand body having migrated up to 230 m and the western part of the sand spits having eroded about 80 m (Fig. 6).

Fig. 6
figure 6

Comparison of the results of GPS-survey of different years

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For two km west of river mouth (Fig. 6) longshore sand waves have been formed over the last 20 years. The size of the longshore sand waves increases to the east (the wave amplitude and the length of adjacent straight segment of shoreline is 15 m and 100 m for the westernmost cusp; 30 m and 250 m for the second cusp; 70 m and 400 m for the third; 100 m and 900 m for the easternmost cusp). The shoreline therefore consist of straight coastal segments, accretionary areas (distal parts of straight coastal segments) and erosional areas (concave coastal segments to the east of the accretion zones).

Annual GPS surveys of the shoreline show the rate of longshore sand wave movement in easterly direction is from 13 to 20 m per year.

To the west of the River Tchernaya mouth a large accretionary sand body was formed over the last 2 decades. Topographic charts, aerial and satellite photos and GPS survey results show three stages of sand body generation a) the beginning of the sand spit growth in an easterly direction (1982–1986), b) the extension of a narrow sand spit to the mouth of small river and the enclosure of a lagoon between the spit and former shoreline (1989), and c) the spit become wider and the lagoon infilling (Fig. 7).

Fig. 7
figure 7

Costal line changing as a result of intensive sand drift of eastern direction (south coast of the Gulf of Finland)

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To the east of the mouth of the River Tchernaya a hooked spit is formed. On the distal (eastern) part of the spit the accretion processes is continuing, while the attached part of the spit is intently eroding.

Unlike other parts of the bed of the Gulf of Finland the underwater coastal slope is very smooth here, with the average incline being only 0.0010. The 1 m isobath is 500–800 m and the 5-m isobath is 2.5–3.5 km from the shoreline. The nearshore seabed is comprised of sand. Along the shore there is a sand accretion terrace up to 1–2 km wide. A sediment deficit is therefore not a driver of the coastal dynamics.

The shoreline orientation prevents south-westerly and westerly storms from impacting the shore. Neotectonic movement is probably the most important process driver of coastal evolution with recent tectonic sinking being important on this part of the coast (Yaduta and Dvernitsky 1997). Recent acceleration of erosion processes may be caused by submarine sand mining which took place within the “London Shallow” (to the west of study area) in 1960s–1990s.

Discussion and conclusion

Erosion in the coastal zone of the eastern Gulf of Finland is influenced significantly by rapid changes to water level during St.Petersburg floods, accompanied by severe storms with winds from the west and south-west.

The highest floods were induced by progressive waves in resonance with cyclones moving along the Baltic Sea and the Gulf of Finland. After entering the eastern part of the gulf, the long wave bound due to narrowing of the gulf cross-section, and water level sharply rises in height as a result significant shallowing. Seiching may also contribute to the water level fluctuations (Nekrasov et al. 1999). A history of floods produced by the St.Petersburg Regional Center for Hydrometeorology and Environmental Monitoring for St.Petersburg from 1703 to 2008 shows 307 floods higher than 160 cm. During the last 300 years, three catastrophic floods occurred in 1777 (3.21 m higher sea level), 1824 (4.21 m) and 1924 (3.80 m) (www.meteo.nw.ru, www.eurosion.org). No regular pattern of floods has been found (Nekrasov et al. 1999).

Some scientists suggest that the main reason for an intensification of erosion processes is an increase of storm activity both in the Gulf of Finland and in the whole Baltic Sea (Geology of the Gulf of Finland 1992). A recent study of marine winds and storminess has shown significant increase to both in the Baltic Proper (Soomere 2001) and in western part of the Gulf of Finland (Orviku et al. 2003; Soomere et al. 2008).

In the Baltic Region considerable warming has occurred during the winters. On the Estonian coasts adjoining the Russian part of the Gulf of Finland over the last 20–30 years the most marked coastal changes resulted from a combination of strong storms, high sea-level induced by storm surge, an ice-free sea and unfrozen sediments (Orviku et al. 2003). It is important to note that catastrophic erosion of the dunes (Fig. 2) was observed in January 2007 under exactly the same hydro-meteorological and litho-dynamic conditions. Recent studies have shown that the most extreme erosion events are controlled by a specific combination of hydrometeorological factors. Such events occur when three unfavorable conditions occur simultaneously: (i) long-lasting westerly or south-westerly storms, (ii) a high water level (more than 2 m above the mean level as measured at the Gorny Institute observation post, and, most importantly, (iii) the absence of stable sea ice during such events. During the last decade, the frequency of occurrence of this combinations of events, especially of late freezing, has increased (Ryabchuk et al. in press).

It is important to mention that according to a modeling study (Konstantin Klevanny, personal communication) when the Flood Protection Facility is completely constructed, the coastal areas adjacent to Neva Bay (including the historical centre of St.Petersburg) will be protected from floods. On the other hand, within the eastern Gulf of Finland outside the dam, water levels during floods will be higher than now. The model shows that near the Kurortny District shore the water level during floods will be 20–30 cm higher than before the Flood Protection Facility construction. In this case extreme erosion events will probably become more frequent.

Alternating sections of stable and intense eroded areas can be caused by difference in the geological structure and the morphology of the nearshore coastal slope.

The analyses of the submarine coastal slope morphology of the northern coast of the Gulf of Finland within Kurortny District showed some points of sediment loss: (i) the sand beaches of Sestroretsk do not grow in spite of longshore sediment flow discharge in the area, due to the steep slope of submarine terrace, which leads to sediment loss; (ii) the longshore submarine terrace of the northern coastal zone with surface at the depth 3–5 m, which can protect the shore from the most severe storms, is eroded and its marine edge has shifted landward; (iii) the erosion runnels, which are located at the depth from 8 to 12 m, where near-bottom currents remove sand material seaward.

The intense erosion on the southern coast has different causes. A wide shallow water sand terrace which is a source of sediment material should prevent coastal erosion. However, as opposed to the tectonically stable northern coast where the rate of vertical tectonic movement is almost 0, this part of coastal area is sinking with an average rate of tectonic movement about 2 mm per year. Another possible reason of coastal process intensification could relate to sand extraction. In 1970s and 1980s underwater sand mining took place in the “London Shallow” which is located to the east of Lebyazhye. The “London Shallow” was the main source of sand material for supplying the coast in the study area.

Since the end of 1990s coasts of the Russian part of the Gulf of Finland have become the areas of intense anthropogenic activity. Over the last decade three large port complexes (in Primorsk, Ust-Luga and St.Petersburg) were built or significantly expanded, and as a result ship traffic is increasing. Some ongoing and planned projects are connected by dredging. In the eastern part of Neva Bay between 2006 and 2008 there has been reclamation of 476 hectares for the New Sea passenger port; with another 300 hectares planned near Sestroretsk town. In 2010 the “Nord-Stream” submarine gas pipe-line will commence construction. Another significant coastal zone development is for recreation. Seven nature protected areas (including three RAMSAR Sites) are situated on the coasts of the Eastern Gulf of Finland and in adjacent near-shore water. Six more Nature Reserves (Nature Conservation Atlas, 2006) are planned. Sustainable development requires ICZM methodology, an important aspect of which is understanding the natural (hydrometheorological, geological, geomorphologic) and anthropogenic drivers of coastal dynamic processes.

The main conclusions of this study are as follows:

The coastal dynamics of the Eastern Gulf of Finland are more active that was previously understood with many sections of coast in the easternmost part of the gulf being heavily eroded. Maximum rates of shoreline recession in some areas reach 2 m/year.

Recently extreme erosion events in the Eastern Gulf of Finland are being observed more frequently.

The most extreme erosion events are observed when three hydrometeorological factors act together: long-lasting westerly or south-westerly storms, high water levels, and the absence of stable sea ice. Over the last decade the frequency of occurrence of these combinations has increased due to late freezing.

As the coastal zone of the Eastern Gulf of Finland is composed of Quaternary deposits (glacial till, sands and clay) along its whoelelenght, the most important geological factor for coastal erosion are the neotectonic movements.

The morphology of nearshore profile plays an important role in coastal processes. In the northern coastal areas the most important causes of sediment loss are (i) the steep slope of narrow submarine terraces within the area of sediment drift discharge, (ii) erosion of the alongshore submarine sandy terrace and (iii) canyon-like erosion runnels at a depth 8–12 m.