Coastal Processes of the Russian Baltic (Eastern Gulf of Finland and Kaliningrad Area)

Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

Accepted Manuscript Quarterly Journal of Engineering Geology and Hydrogeology

Coastal processes of the Russian Baltic (eastern Gulf of Finland and Kaliningrad area)

Daria Ryabchuk, Alexander Sergeev, Evgeny Burnashev, Viktor Khorikov, Igor Neevin, Olga Kovaleva, Leonid Budanov, Vladimir Zhamoida & Aleksandr Danchenkov

DOI: https://doi.org/10.1144/qjegh2020-036

Received 11 February 2020 Revised 18 May 2020 Accepted 2 July 2020

© 2020 The Author(s). This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/). Published by The Geological Society of London. Publishing disclaimer: www.geolsoc.org.uk/ pub_ethics When citing this article please include the DOI provided above.

Manuscript version: Accepted Manuscript This is a PDF of an unedited manuscript that has been accepted for publication. The manuscript will undergo copyediting, typesetting and correction before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Although reasonable efforts have been made to obtain all necessary permissions from third parties to include their copyrighted content within this article, their full citation and copyright line may not be present in this Accepted Manuscript version. Before using any content from this article, please refer to the Version of Record once published for full citation and copyright details, as permissions may be required. Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

Coastal processes of the Russian Baltic (eastern Gulf of Finland and Kaliningrad area) Daria Ryabchuk1*, Alexander Sergeev1, Evgeny Burnashev2, Viktor Khorikov1, Igor Neevin1, Olga Kovaleva1, Leonid Budanov1, Vladimir Zhamoida1, Aleksandr Danchenkov3, 4

1 A.P.Karpinsky Russian Geological Research Institute (VSEGEI), 74, Sredny pr., St.Petersburg, Russia, 199106; *Correspondence ([email protected]) 2 State Budgetary Institution of Kaliningrad Region “Baltberegozaschita”, Svetlogorsk, Khutorskaya st. 1, 238560 3 Shirshov Institute of Oceanology, Russian Academy of Sciences (IO RAS), 36, Nahimovskiy prospekt, Moscow, Russia, 117997 4 I. Kant Baltic Federal University, 14, Nevskogo A. str., Kaliningrad, Russia, 236016.

Keywords: SE Baltic, Eastern Gulf of Finland, erosion, geotechnical properties, monitoring, alongshore sediment transport

Abstract Results of onshore and offshore coastal zone monitoring of the Russian Baltic reveal high intensity and recent acceleration of coastal dynamics caused by increasing frequency of hydrodynamic extreme events and anthropogenic impact on diverse geology. In the eastern Gulf of Finland stable coasts dominate, but the local shoreline recession rate is up 2.0 m/year, reaching 5 m in one extreme storm event; the coastal zone of the Kaliningrad area is essentially diverse; the Western coast of the Sambia Peninsula is controlled by anthropogenic impact linked to exploitation of geological resources. Here, when artificial sediment supply from amber opencast mines increases, the beaches are advanced; when the input is interrupted, the shoreline retreat reaches 10–20 m/year. Along the northern coast of the Sambia Peninsula active landslides and beach degradation dominate. Large areas of pre- Quaternary deposits, outcrops and boulders, in the nearshore provide evidence of offshore sediment deficiency. Coastal geological hazards can be considered to be climate-dependent. A comprehensive understanding of the main trends of climate change is important for predicting and mitigating future damage to coastal infrastructure and for selecting adaptation strategies.

Introduction

The BalticACCEPTED Sea is an intra-European, transboundary MANUSCRIPT water basin that is densely populated and has a high economically developed drainage area (Figure 1, upper right panel). Geological mapping of the Baltic Sea floor is one of the most interesting and challenging tasks of EMODnet-geology project as the seamless maps are compiled by ten partner institutions from nine countries, each with a long history of different mapping approaches and classifications. From the perspective of EMODnet-geology Work Package 4 (coastal behavior), the most remarkable feature of the Baltic Sea is its great variety of coastal types. These depend largely on differences in geological structure of the various regions of the Baltic area, and also on the diversity of land movement with sinking south-western and uplifting north-eastern coastal Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

areas (Harff et al. 2011; Harff & Meyer 2011). The main geological features of the Baltic Basin are controlled by its position between the Fennoscandian crystalline Shield represented by Precambrian magmatic and metamorphic rocks, and East European platform, characterized by Phanerozoic sedimentary cover whose thickness increase from north-east to south-west by up to several thousand meters (Šliaupa & Hoth 2011). Hard metamorphic and magmatic rocks of the Scandanavian Shield outcrop along the northern coast of the Gulf of Finland, Gulf of Bothnia and western Baltic Proper. Quaternary deposits are widespread along the southern Baltic coasts but in the areas where these are eroded the coastal cliffs are composed of relatively easily erodible sedimentary rocks: Ordovician and Devonian (in Estonia), and Paleogene - Neogene (in the South-Eastern Baltic including Kaliningrad area). Rates of glacio-isostatic rebound along the Baltic coast vary from -1.5 mm/year, in the southeastern Baltic, to +10 mm/year in the top of the Gulf of Bothnia (Harff et al., 2017). Wave impact on the Baltic Sea coastal zone differs significantly depending, for example, on geographical position, shoreline configuration and wave fetch.

The coastal zone of the Russian Baltic consists of two distinct areas – the easternmost part of the Gulf of Finland and SE Baltic within the Kaliningrad area (panel B, Figures 1 and 5). The southern coast of the Russian Gulf of Finland experiences similar processes to adjoining Estonian shores, whilst the skerries of north-west resemble much of the Finnish coast of the Gulf. The Kaliningrad area coasts consist of high cliffs of the Sambia Peninsula and two significant sediment accretion bodies – the Vistula Spit, shared with Poland at the SW, and the Curonian Spit, the north-eastern half of which lies in Lithuania. Both segments of the Russian Baltic are characterized by intense coastal erosion, with a wide spectrum of landslides evident on the cliffed coasts of the Sambia Peninsula.

Coastal areas and beaches of both parts of Russian Baltic are highly valuable, from both recreation and nature protection perspectives, and are under the great anthropogenic pressure. The urgent need for an effective coast protection strategy is recognised by local authorities and is in the early stages of development. Such a strategy needs to be based on a clear scientific understanding of natural coastal processes, considering marine and geological factors and identifying the main trends of current and future shoreline evolution.

This paper identifies the main trends of coastline evolution, calculating rates of shoreline retreat or advance, mapping the coastal geology and identifying coastal erosion “hot-spots”. The aim is to link the occurrence of different lithologies with different coastal behaviours, revealingACCEPTED natural and anthropogenic driving MANUSCRIPT forces of coastline dynamics and proposing a strategy for coastal management and protection.

There is a long history of previous investigations, with the first scientific investigation of the South-Eastern Baltic geology and coastal processes at the beginning of 20th century. Abromeit et al. (1900) described geomorphic features of the coastal zone and the problem of dune stability. Tornquist (1914) considered problems of sediment drift and storm impact on the Curonian spit. Based on field observations during the winter storm of 9–10 January 1914, he identified that during a single extreme storm event the coastal system may lose twice as much material as it accumulates over a whole year. In the vicinity of the Curonian Spit, data Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

on the geological structure of the Quaternary deposits and erratic blocks of Cretaceous rocks were published in 1919 (Wichdorff 1919).

The first map of Quaternary deposits of the Kaliningrad Region was compiled by Vereisky in 1946. Between 1958 and 1967 complex hydro-geological investigations enabled development of on-land geological, hydro-geological and geomorphic maps at a scale of 1:200 000 (Zagorodnyh & Kunaeva 2005). In 1960, the first aerial survey of the South-Eastern Baltic coastal zone was carried out by the Atlantic Branch of the Institute of Oceanology (ABIO RAS) (Boldyrev et al. 1990). At the same time, repeated bathymetric measurements accompanied by sediment sampling, beach levelling, geomorphic observations by scuba, sampling of suspended sediment and measurements of hydrodynamic parameters (waves and current) were carried out (Aibulatov et al. 1966). Further studies of the coastal dynamics of the Kaliningrad Region have continued since 1972 by the Agency of Coastal Engineering later reorganized as the Bureau “Baltberegozashita” (Boldyrev et al. 1990; Ryabkova 2000; Boldyrev & Ryabkova 2001).

Hydrological studies, carried out by the ABIO RAS from 1980 to the late 1990s, classified near-bottom currents from the shoreline to the outer boundary of the coastal zone and determined the existence of sediment transport towards the east (Babakov 2002). The most recent overview of coastal geology is presented by Zhindarev et al. (2012).

Since 2000 the Laboratory of Coastal Systems of ABIORAS has conducted coastal monitoring studies along the shores of the Kaliningrad area. Numerous annual cross-shore profiles have been measured, using permanent concrete bench-marks as fixed-points to enable the calculation of coastal erosion rates (Bobykina & Boldyrev 2008). Coastal zone and nearshore bottom dynamics of the Curonian Spit are analyzed by Zhamoida et al. (2009).

The geology and geomorphology of the EGoF coasts have been studied since the 1920-1930s (Yakovlev 1925; Markov 1931). Coastal processes were first investigated by Leningrad University in the 1970s (Barkov 1989). An overview of the geology, geological history and the first classification of the coasts of the EGoF area is presented by Raukas & Hyvärinen (1992). The first geological description of the Russian coast of the Gulf of Finland was published by K. Orviku in 1991 (Orviku & Granö 1992). The authors of the current paper discuss some aspects of coastal zone dynamics e.g. Ryabchuk et al. 2011a, b, 2014; Spiridonov et al. 2011; Kosyan et al. 2013; Sergeev et al. 2018.

However,ACCEPTED this current paper presents the MANUSCRIPT first regional study based on a combination of comprehensive geological and geomorphological datasets and results of long-term coastal monitoring.

Materials and methods

Field work. Since the 1980s the Russian Geological Research Institute (VGEGEI) has carried out geological mapping and research, and since 2011 there has been annual State (Federal) monitoring of the geological environment of the Russian Baltic and the Regional Program of St. Petersburg City Coast Protection Strategy development (2015–2016). The main Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

methodological approach of coastal zone monitoring combines methods of onshore monitoring (remote sensing data, observations, levelling, terrestrial laser scanning, unmanned aerial vehicle survey, ground penetration radar (GPR), profiling) and offshore survey (e.g. sub-bottom profiling (SBP), side-scan sonar profiling (SSSP), sediment sampling, and submarine video survey; for some areas also multibeam profiling). Offshore research maps the nearshore bottom to reveal areas of bottom erosion and an absence of recent sediment cover (sands, gravel). In 2015–2019 engineering geological studies of coastal transects, from shoreline to cliff edge, were carried out by VSEGEI. Five transects were monitored annually in the Kaliningrad coastal zone and three in the eastern Gulf of Finland (EGoF). Research included sediment sampling for grain-size analysis and determination of physical and mechanical properties, and strength testing of clays with portable penetrometer and field vane tests.

In the SE Baltic annual monitoring measurements have also been undertaken by the State Budgetary Institution of Kaliningrad Region (“Baltberegozaschita”) and Atlantic Branch of P.P. Shirshov Institute of Oceanology (ABIO RAS). In 2000–2002, 70 regular ground marks were established for repeat measurements and since 2008 the number has been increased to 285 marks. Monitoring includes measurement of lithology, sediment characteristics and relief of submarine coastal slope, beach and foredune dynamics. These 285 ground marks are installed at 500 m intervals and georeferenced (WGS-84, 1977 Baltic altitude system) along 145 km of the coastline. Measurements are carried out both seaward and landward from the ground marks, with data sets including distance between ground mark and coastal escarpment base and edge, foredune base, shoreline. Comparative analyses of results allows different parameters of coastal zone dynamics to be distinguished. Precision of measurements is at cm scale, not exceeding several cm. As a result, a significant dataset has been collected for the last ten years (2008–2018) for all coasts, and for a period of nineteen years (2000–2018) for most representative coastal segments. These data can be used to analyse main coastal dynamic trends, to identify key driving forces (storm activity, storm frequency etc.), and to calculate coastal sensitivity and vulnerability in relation to geological properties. Coastal monitoring also includes remote sensing data analyses, aerial laser scanning, aerial photo survey, technical monitoring of coast protection constructions, bathymetric survey and sediment sampling of nearshore bottom, analyses of geodesic, hydrometeorological, geological, environmental and hydrotechnical surveys and scientific publications.

Retrospective analyses of topographic maps, aerial photographs, and remote sensing data (RSD)ACCEPTED. Topographic maps of 1:25,000 scale,MANUSCRIPT based on surveys of late 19th century and published in the early 20th century, were used in this study to determine the long-term trends of coastline change on the EGoF. Digitizing and GIS analyses (ArcGIS 10.0) of 89 topographic map sheets of 1:50,000 scale, published in the 1960s and covering most of the studied coastal areas, allowed us to trace specific relict coastal accretion forms located at the present time at different altitudes thus revealing coastal line changes. Georeferencing of these maps was executed based on the position of the same objects (buildings, roads) which are preserved since that time. To analyze the long-term coastal transformation of Kaliningrad coasts, we digitized four archival topographic maps of 1:25,000 scale (Gr. Dirschkeim, Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

Rauschen, Neukuhren, Palmnicken), published in 1926. Results of retrospective analyses showed a high accuracy of topographic maps, allowing us to trace the coastal escarpment position and calculate the rate of its retreat relative to modern satellite image from 2013 (available in Google Earth).

Recent coastal dynamics of the EGoF were studied using satellite imagery available via Google Earth for most parts of the coast. For the period 1984-2005, we used Landsat 1-7, cell size from 80 m to 30 m, and for the period 2005-2018 using high-resolution satellite images with cell size of several tens of centimeters. For remote sensing data analyses of the Island Kotlin coastal dynamics, aerial photos from August 15 1939 were used. For the Southern coast of the Gulf, in the vicinity of Bolshaya Izhora village, we used high resolution air photos from 1990. Analyses of the full set of satellite images enabled us not only to fix the initial and final points of the coastline position, but also to identify the dynamics of its transformation in relation to geological composition, including the formation, mobility and destruction of sand spits and bars. For some of the most dynamic coastal areas, analyses are also based on annual field observations, levelling and very high resolution space images retrospective analyses available from earlier published studies (Leont‟ev et al. 2011; Ryabchenko et al. 2018; Sergeev et al. 2018).

Terrestrial Laser Scanning (TLS) In the Sambia Peninsula coast, terrestrial laser scanning (TLS) data were collected in August 2016 and August 2017 using the TOPCON GLS-1500. The accuracy of determination of distances and angles is 4 mm for 150 m of measurements, and the angular accuracy is 2.9e-5 rad. The scanning system is equipped with a sensor system for self-calibration and elimination of levelling errors, a collimator and a rotation system that starts before each launch which does not require manual calibration (Topcon 2010). Co- registration of TLS data was performed by the back-sight method using the target (BS) installed on the tripod, as well as the GNSS receiver TOPCON GR-5. The differential correction was obtained from the internal network of base stations. To compare the results of TLS point clouds, digital elevation models (DEM) were developed using ArcGIS 10.0 with the Natural Neighbor tool for linear interpolation of point data. The GRID cell size was set at 0.1 m.

In the EGoF coasts TLS was carried out over 2012–2017 by “Alpha-Morion Ltd.” using the RIEGL VZ-400 (Austria) from twelve stable points (scan positions). Geodetic referencing to the local coordinate system SK64 and the Baltic System of Heights 1977 was established usingACCEPTED a Trimble R8 and Javad Legacy-E MANUSCRIPT satellite. Post-processing was performed using “Pinnacle” software. Horizontal and vertical fixes of the position marks were made using a LEICA TS06 Ultra (2") (Austria) total station.

Data Managements and GIS. Results of annual monitoring are collated as GIS maps. Results received in the frame of SE Baltic coastal monitoring are integrated within Informational System of Kaliningrad Region, using an on-line resource (http://www.bbz39.ru/ipas) for state coast protection strategy development.

Results Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

Eastern Gulf of Finland

The Russian part of the Gulf of Finland shoreline, not accounting for islands, is approximately 520 km in length (Figure 1). A key feature of the eastern Gulf of Finland is a very low rate of uplift, 0 to +3 mm/year, and a near zero rate of recent sea-level change (Gordeeva & Malinin 2014; Harff et al. 2017). The northern coast, from the Finnish-Russian boundary to the Beriozovy Archipelago, consists of skerries with numerous islands and small barrow bays formed by igneous and metamorphic rocks and partly covered by till. The most widespread coast type, formed as a result of erosion of Late Pleistocene moraine, is characterized by erosion scarps fronted by boulder benches in the near-shore zone. Our results indicate that the embayed coasts are straightening as the result of sediment accumulation. Sand accretion coasts with wide, 50–150 m, stable sand beaches are observed in the Narva Bay and in front of Sestroretsk town. The easternmost part of the studied coasts, within Neva River mouth, has been largely transformed by technogenic processes. About 70% of its coast (82 km over 118 km of shoreline), consists of embankments, coastal protection structures and other technogenic constructions. The St. Petersburg Flood Protection Facility (FPF)(Figure 1) has played an important role in recent coastline evolution.

Since the foundation of St. Petersburg hazardous floods have threatened the city‟s population and the earliest plans to protect the city date from just after the catastrophic flood of 1824. In 1858, in the Report to The Russian Geographical Society, E. Tillo presented eight different potential projects for the flood defense of St. Petersburg. One of these proposed projects was developed in 1824-1827 by professor Pierre Dominic Basen. There were no further developments until after the Second World War when discussions began again at a new, more technical level. As a consequence in 1979 the construction work began on a huge hydrotechnical structure, the Flood Protection Facility (FPF). In the1990s the FPF construction was interrupted due to need to carry out an ecological risk assessment, but in late 2000s it was continued. Since 2011 the FPF, one of the largest hydrotechnical constructions in the Gulf of Finland (total length 25.4 km, height 6.4 m above the average long-term water level), has been fully functional (Ryabchuk et al. 2017). The FPF consists of eleven dams, six water sluices and two navigation gates (https://dambaspb.ru/#intro). Its functioning is very important to protect the city of St. Petersburgh from flooding, but in the 1990s there was a discussion about its possible impact on the environmental status of the EGoF and, especially, Neva Bay. Particular consideration was given to the risk of increasing water and bottom sediment pollution with hazardous substances, such as heavy metals, as a result of the interactionACCEPTED of the FPF with St. Petersburg MANUSCRIPT waste waters. Testing and monitoring of bottom sediment revealed no negative impact of the FPF, instead indicating a general decreasing trend in the concentration of hazardous substances since the 1980s (Ryabchuk et al., 2017). The decline in heavy metal concentrations was attributed, in the main, to temporal decreasing anthropogenic loads in the 1990's, and later (since 2000s) associated with efforts of the VODOKANAL State Enterprise in improving St. Petersburg water treatment since the beginning of 2000s (http://www.vodokanal.spb.ru/en).

Low coasts dominate within the EGoF; the average height of the recent marine terrace is 1–2 m, with the exception of 30 m high cliffs occurring in unconsolidated sediments near Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

Krasnaya Gorka village. The coasts of the EGoF are exposed to the influence of multi- directional waves. The most dramatic impact to the coasts is brought by western and south- western waves associated with the prevailing wind direction (Ryabchuk et al. 2011a), with the coasts of the Kurortny region, village Lebyazhye, Kotlin Island, Narva Bay being most vulnerable. Wave energy along these coasts increases during the autumn and winter periods (Kovaleva et al. 2017) when unprotected and exposed coasts can retreated significantly. However, the erosive effects of the waves may be mitigated by stable ice cover which usually forms in late November (Soloshchuk 2010) thus reducing the erosional consequences usually associated with surge storm events. During calm spring and summer periods waves and currents induce normal long-shore and cross-shore sediment transportation which does not significantly reshape the beach profiles.

According to remote sensing data (RSD) analyses, the coasts of the EGoF can be subdivided into several types: i) erosion dominated (foredune erosion or retreat of the coastal escarpment), ii) accumulative (beach aggradation, stable foredune); iii) intense longshore sand drift sufficient to develope sand spits and longshore sandwaves; iv) stable (skerries and technogenic) (Figure 1). Combined analyses of monitoring observations and remote sensing data have enabled identification of the most dynamic parts of the EGoF coast: the shores of the Kurortny district of St. Petersburg, the western coast of Kotlin Island and the southern coast of the gulf between Lebyazhye and Bolshaya Izhora villages.

The average rate of coastal escarpment retreat within erosion dominant coasts is 0.25 m/year. Locally it increases to 1.5–2.0 m/year, and during severe storms the escarpment can retreat landward by up to 5 m per storm (Ryabchuk et al. 2014). It is important to mention that such high-magnitude erosional events have recently become more frequent and have been observed four times since 2004. The coastal area of the Kurortny district is exposed to the greatest erosion under the impact of western and south-western storms. The longest series of leveling measurements of the beach cross-sectional profile and results of repeated terrestrial laser scanning (TLS) survey for the Komarovo village showed that from 1988 to 2018, the average annual beach erosion rate of the beach-face escarpment is 0.9 m/year (Sergeev et al. 2018). This long-term erosion rate masks significant annual variations whereby there may be 0 m of erosion over several consecutive calm years followed by 5 m during an extreme storm event. Similarly, following a series of storms in 2011 the coastal cliff retreated by up to 6.5 m landward. Using only TLS data collected annually from 2012 to 2017 we calculated the volume of sand as a difference between beach surfaces for each year. The totalACCEPTED balance shows a reduction of beach MANUSCRIPT sediments by 413 m³ along a 90 m segment. The average loss of sand as a result of storms over this five-year period was 4.5 m³ per 1 m of shore.

For the western coast of Kotlin Island analysis of remote sensing data for 76 years, using aerial photo of August 15, 1939 and high-resolution satellite image of 2015, shows that along-shore transport of sand material and alignment of the coast contour dominate here with intense erosion of capes and filling of the small bays. Capes are eroded and sediment accumulation is observed in the eastern part of this coastal segment. The average rate of coastline retreat was 0.25–0.5 m/year, reaching 1.2–1.6 m/year on more exposed parts of the Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

coast (Figure 2B). The maximum erosion rate of up to 2 m/year was recorded at the most western part of the island (Ryabchenko et al. 2018).

The coast to the west of the village Lebyazhye (southern coast of the Gulf of Finland) differs from the neighboring shores by the presence of an active coastal cliff up to 15–20 m high and composed of sandy sediments and boulder sandy loams (silty-clay with boulders). Boulders and coarse-grained sand prevail on the surface of the beach. The lower part of the cliff is composed of sub-horizontal layers of boulder-pebble deposits. Several of these layers can be traced along the cliffs because of their large quantity of boulders. The upper part of the cliff is composed of layers of sand, pebbles and gravel. Geotechnical properties of deposits are shown in the Table on Figure 3.

Repeated TLS surveys of the beach surface and coastal cliff in 2016 and 2017 showed that slope erosion occurs primarily due to intense landslides triggered by a surplus rainfall. The volume of material displaced down the slope reached 5.8 m³ per 1 m of shoreline. An analysis of satellite images, from 2005 to 2018, showed that the edge of the coastal escarpment retreated landward by 13 m, approximately 0.8 m/year. Sand accretion is observed locally, mainly near the mouths of rivers, and results in the formation of stable beaches of up to 100 m wide. There are no advancing sand beaches within study area.

Dynamics of the spit coast are most active. Within the north-eastern coast of the Gulf there are several small, up to 100 m long, short-term sand spits shifting in an eastern direction at an average rate of 30 to 60 m/year observed between 2013–2018 (Figure 1). In the southern coast, near Bolshaya Izhora village, much larger sand spits of up to 1100 m long and 200 m wide occur (Ryabchuk et al. 2011b). Special features of the coastal zone geological structure here include a sufficient volume of sand material, produced by onshore and offshore erosion of the Holocene sand terrace, which has resulted in development of dynamic forms of coastal relief - “alongshore sandy waves” (Leont‟ev et al. 2011). The shoreline contour of the seaward edge of the contemporary marine sand spit is characterized by a smooth curving shape. An important feature of the observed large sand cusps, longshore sand waves, is an increase in their size, both length and amplitude, in the eastern direction. The amplitude of the cusps grows to the east from 15 m to 100 m with downdrift straight shoreline segments. Comparison of remote sensing data and annual field monitoring results showed that over the period of observations, from 2011 to 2018, the annual alongshore “waves” displacement reached is 8-20 m/year (Figure 4). While the beach is eroded from the west side of the protrudingACCEPTED section of the coast (“waves”), theMANUSCRIPT whole sand wave feature is migrating along the coast in an easterly direction. Similar coastal forms are observed along the western shore of Kotlin Island. The development of these longshore sand waves is explained by the fact that the prevailing waves, induced by the westerly winds, are propagated almost parallel to the shoreline.

Near-shore areas of the most heavily eroded segments of EGoF coastal zone are fully covered by side-scan sonar profiling survey. These surveys have revealed the occurrence of vast boulder-pebble sediment areas, dominating at water depths of 0–5 m, along the northern coasts of the outer Neva Bay estuary, the nearshore of Kotlin Island and the submarine Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

periphery of some capes. Results of these investigations have revealed a nearshore sediment deficit (Ryabchuk et al. 2011a; Ryabchenko et al. 2018), and the results presented here support close links between sediment balance offshore and the onshore rate of coastal erosion.

South-Eastern Baltic

The coasts of the Kaliningrad sector of the SE Baltic can be genetically subdivided into the erosion-dominated Sambia Peninsula shore and two accretion-dominated spits – Vistula and Curonian. According to morphology and recent processes trends, ten different coastal subtypes can be distinguished (Petrov 2010).

The shoreline shape of the Sambia Peninsula (Figure 5), with alternation of capes and bays, is caused by long-term selective erosion of coastal cliffs that are composed of unconsolidated sandy and clayey Paleogene, Neogene and Quaternary deposits (Zhindarev et al. 2012). Cliff height decreases gradually in eastern and southern directions from 55 m to 5–10 m. The escarpments of both the Western Sambia Peninsula, south of Cape Taran, and the Northern Sambia, east of the Cape, are dissected by numerous ravines.

Study of the coastal escarpment cross-sections shows that they consist of alternating relatively thin (1–10 m) layers of variable grain-size composition consisting of sands, sandy loam (silt), clayey loam (silty clay) clays and course grained sediments. The geotechnical properties of these layers differ slightly but are predominantly unconsolidated and easily erodible ((Figures 6, 7).

The cliff near the village of Donskoye has a very heterogeneous structure. Unconsolidated deposits of different grain size composition form many layers. Sands, as shown in Figure 6, vary in grain size from silty sand to coarse-grained sand. Clay layers of the cliff are thin with a moisture content of 23–26% and a density of 1.87–2.02 g / cm3. Cemented sands of the upper part of the cliff, where the slope angles reach 90 degrees, are characterized by the highest level of mass movement hazard.

The cliff in Filino village (Figure 7) is composed mainly of medium-grained sandy sediments and in the lower part of the cliff they are densely folded forming a vertical wall. Sands of the upper part of cliff are more friable. The top 3–4 m are represented by silt with a high content of boulders and pebbles and with a low moisture content (16.2%), and a density of 2.11 g / cm3. ACCEPTED MANUSCRIPT

In the southeastern part of the Baltic Sea, wave activity due to shallow water and a semi- closed position is determined by the direction of the winds and wave interaction with the bottom of the sea (BACC Author Team 2015). A pronounced annual pattern of wind waves is observed – a decrease in significant wave height during the spring-summer period (0.6–0.7 m) and an increase in the autumn-winter period (0.8–0.9 m) (Rózyński 2010; Zaitseva- Pärnaste et al. 2011). Storm waves, of over 2 m, occur in less than 5% of all observations (Kelpšaite et al. 2008). South-westerly waves (1.4–1.8%), to which both the northern and western coasts of the Sambia Peninsula are exposed, possess the highest frequency. Typical Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

wave periods are 3–6 s (Kahma et al. 2003; Soomere 2008). During the last four decades, associated with a positive NAO index, there has been a significant increase the occurrence of SW winds from 15% to 25% (Kelpšaitė et al. 2011). Positive NAO index air pressure is higher than average over the southern part of the North Atlantic or lower than average over the northern part (Dailidienė et al. 2006). Modern evolution of the Sambia Peninsula coasts is driven by a complicated system of currents, controlled by winds, their directions and underwater slope morphology (Babakov 2002). The most severe erosional events, accompanied by nearshore sediment transfer, are observed during short but intense storms of 1 – 2 days duration. Between these storm events the beach systems are party regenerated (Boldyrev et al. 1990).

Both the Northern and Western coasts of the Sambia Peninsula are characterized by active sediment dynamics (Figure 5). The Western coast of the Sambia Peninsula is an outstanding example of “positive” anthropogenic impact on shoreline evolution whereby large volumes of sediment are provided to the coast from mining activities. Early 20th century topographic maps demonstrate an embayed shoreline. Near Sinyavino settlement the shoreline was embayed at about 150 m, near Yantarny approximately 700 m and, to the south of Okynevo approximately 300 m (Figure 8). Since 1958 the Amber mining factory, located onshore in Yantarny settlement, annually dumped from 1.5 to 4.5 M. tonnes of clayey sand mining waste from amber extraction into the Baltic Sea (Bass & Zhindarev 2007; Bobikina & Karmanov 2009). This dumped material was incorporated into cross-shore and longshore sediment drift. By the 1970s it had resulted in the formation of an 800 m wide and 5.5 km long anthropogenic accretion terrace and local foredune belt along shoreline between Yantarny and Sinyavino. The volume of sediment accumulated in the terrace was about 50 M. m3 of sand. As a result, the coastal cliffs have become inactive and overgrown by vegetation. Since 1971 sediment dumping has moved to Pokrovskaya Bay and the anthropogenic accretion terrace between Yantarny and Sinyavino has begun to erode. Meanwhile, dumping of 20 M. m3 of sediments into Pokrovskaya Bay between 1971and 1986 has resulted in total filling of the bay, shifting the shoreline to what was previously 9–10 m water depth and forming a protective beach in front of Pokrovskoye.

In 2000 sediment dumping was suddenly halted due to the introduction of environmental restrictions. Subsequently coastal erosion has intensified along the whole western coast of the Sambia Peninsula illustrating the sensitivity of the coastal zone to technogenic impact. Sediment supply from even small onshore dumps, of about 100–200 m long, can initiate coastlineACCEPTED progradation of up to 15–20 m per MANUSCRIPT year, while any attempts of illegal amber mining can trigger acceleration of erosion. Landsat images for the study area from 1984, indicate that a wide technogenic terrace still existed at that time. By 2005 coastal erosion had decreased the terrace width, the sand spit was destroyed completely, and an anthropogenic lagoon adjoined the Baltic Sea. The shoreline position was similar to that of 1936 with the exception of the Sinyavino Bay where it was positioned 150–200 m seaward. In 2007 sediment dumping from the Amber Factory resumed with sediment volumes of 0.5 to 1.2 M. m3 annually. This resulted in reducing the coastline retreat to the south of Pokrovskoye village to 0.8–2.5 m/year. Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

Over the last ten years the average rate of coastal erosion of Sambia Peninsula is 0.5 m/year, but the rate and patterns of coastal dynamics differ significantly. The coast between the Baltic Channel and the Taran Cape can be divided into more than ten segments of different dynamics, with rates of shoreline shift from -8.2 to +2.8 m/year (Figure 5). So, locally, recent coastal erosion rates along most part of the western coast of Sambia Peninsula are very high.

In the southern part of Pokrovskaya Bay the recent coastal escarpment retreat rate reaches 2.5 m/year (2008–2018), whilst the long-term rate is 1.4 m/year (1936–2013). The coastal escarpment of the cape Peschany has retreated by 6–16 m between 2008 and 2018, with an average retreat rate over this recent period of 0.6–1.6 m/year, and a longer-term rate of 0.4– 0.5 m/year (1936 – 2013).

The technogenic terrace of the Sinyavino Bay, formed by the Amber Factory mining waste, according to monitoring levelling is eroded and has retreated at a rate of 8.2 m/year in 2008– 2018, while the coastal escarpment here is stable.

Maximal rates of coastal retreat are observed near the Donskoye village. To the north of Donskoye the 15 m high escarpment shifted landward by 80–100 m along 800 m of the coast. Recent and longer-term erosion rates are similar: 1.1 m/year, 2008-2018; 1.1-1.3 m/year, 1936-2013.

An analysis of TLS results has enabled us to demonstrate a mechanism of coastal escarpment destruction and retreat. The escarpment is characterized by steep slopes and high cliffs of up to 40 m. TLS measurements for 40 m high cliffs with steep (70–87°) slopes in the southern part of Donskoye village were made from 11 scan stations in August 2016 and 10 scan stations in August 2017 (Figure 9). DEM analysis allowed us to obtain the volume of changes that occurred at this case study site over one year (Table 3). Due to the high value of coastal land and intense erosion (average rate of shoreline retreat 0.25 m/year, and maximal rate up to 1.4 m/year), the total length of coast protection structures on this stretch of coastline is 10.7 km. But, unlike the Western coast, technogenic impact on the Northern coast of the Sambia Peninsula has not changed the main trends of natural processes.

To the west of Filino village the coastal areas are susceptible to large landslides, of several hundred metres in diameter, due to the combination of heterogeneous cliff geology and hydrogeology. Dense ferruginized Paleogene sandstones outcrop in the lower sections of coastal cliffs (up to 10–12 m), while the upper part consists of unconsolidated Neogene sandy clay (Figure 5 B). Cliff destruction caused by debris flows and landslides is the predominant processACCEPTED along with erosion at the toe of theMANUSCRIPT cliff. The long-term rate of coastal escarpment retreat is 0.1 m/year (1936–2013) and instrumental measurements of 2008–2018 have shown the same erosion rate. This is because, in 1987–1991, a complex coastal protection project was implemented in Filino Bay. The slope itself was engineered to a new shape, large volumes of sediment were used for beach nourishment, and wave absorbers were constructed in the backshore. The program included reshaping of the cliff height up to 44–47 m. The most eroded part of the cliff, composed of Neogene sands, was removed and the residual material (2.3 M. m3) was dumped in the nearshore. To the west of the dumping site at Filino Bay this increased the beach width by up to 140 m along a segment of approximately 2.5 km, and the Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

beach of the Primorye village was widened to 110 m. In addition, this sand entered the longshore transport system and maintained the net sediment balance of the Svetlogorsk Bay for the next 5 years (Boldyrev & Ryabkova 2001).

The geological structure of the coastal zone between Filino and Otradnoye villages is very different, with local capes formed of glacial till thought to be the remains of an end-moraine structure (Zhindarev et al. 2012). Along this stretch of coast, glacial tectonics and selective denudation have resulted in the formation of several valleys perpendicular to the recent shoreline. At the present time these valleys have associated with them intense landslides and surface runoff flow processes. Mass movement and erosion processes within coastal zones of Otradnoye village and Svetlogorsk town are very rapid. There are several coastal segments straightened by various types of hard coastal protection structures constructed in 1960s– 1980s but since beginning of 2000s these have had a less positive effect. Longer-term (1936– 2013) rate of coastal escarpment retreat is up to 0.3 m/year. Recent coast protection measures have stabilized the escarpment.

Between Svetlogorsk and Rybnoye villages, the height of the coastal cliffs declines due to occurrence of wide palaeo river valley. Here the longer-term rate of coastal escarpment retreat reaches 0.2 m/year (1936-2013), whilst the recent rate is reduced to 0.9 m/year (2008- 2018). To the east, towards the cape Kupalny escarpment which consists of sandy and clayey loam (silty clay), the recent retreat rate decreases to 0.3 m/year. But the longer-term rate remains at 0.2 m/year. The long pier of the Pionersky harbor, perpendicular to shoreline, has caused the formation of a stable sandy beach to the east of construction. From the Pionersky to the cape Gvardeisky, with the exception of local areas with coast protection structures, mass movement and erosion processes are very active. Here, longer--term rates of coastal escarpment retreat are 0.4–0.7 m/year (1936-2013) and recent rates have increased to 0.9 m/year (2008-2018).

Offshore research of the marine periphery of the Sambia Peninsula has revealed the wide distribution of boulder bottom and pre-Quaternary deposits and a lack of sand material in the nearshore so there is limited potential for onshore movement of sand to maintain beach volumes (Information…, 2014). Discussion and recommendations for coastal protection

Analyses of archive maps, remote sensing data and monitoring measurements reveal high erosion rates within most valuable, from recreational point of view, segments of the coast of both ACCEPTEDRussian sectors of the Baltic Sea. Moreover, MANUSCRIPT the comparative study of longer-term and recent erosion rates of SE Baltic and monitoring observation in the EGoF coastal zone demonstrate a recent acceleration of erosion within most parts of study area coasts. The geological and geomorphic factors determine the long-term coastal zone evolution. The most important prerequisite for the relatively rapid coastal erosion in the Russian Baltic coastal zone is the geological composition and properties of the coastal deposits.

The coasts of the EGoF mostly consist of easily erodible Quaternary deposits (clays and sands). They evolve under an overall sediment deficit in the nearshore which is partially augmented by numerous boulder belts formed as a result of glacial till erosion. Coastal cliffs Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

of the SE Baltic are composed of unconsolidated sandy and clayey Paleogene, Neogene and Quaternary deposits. The relatively small thickness of the layers (1–10 m), changeable grain- size composition (alternating clayey sands, sands and sandy clays, clays and coarse grained sediments), and multiple points of spring water discharge from three aquifers in Neogene deposits predetermine the conditions for active mass movements. Coastal erosion, coupled with surplus rainfall, is one of the most important triggers of landslides. The main driving forces of the cliff landslides are wave erosion at their foot, frost weathering and precipitation. Fluvial processes in which temporary waterways in the coastal ledge, fed by precipitation, produce channels, wash away the material and cause instability of the gulley walls. Results of offshore investigations reveal a significant sediment deficiency in the nearshore of both study areas, and this is one of the most important reasons of active coastal erosion.

Analysis of extreme water levels for the whole Baltic Sea showed that the amplitude could reach 3 m for the SE Baltic and 3.5 m for the EGoF for the period 1960–2010. The region of the EGoF suffers from the most dangerous storms due to particularities of the atmosphere movement (Wolski et al. 2014). Geographical distribution of the storms across the Baltic Sea demonstrates a higher storm occurrence (more than 300 for the period 1960–2010) at the EGoF compared with the SE Baltic (100–200 for the same period) (Wolski et al. 2014).

To demonstrate the changes an analysis of archival wind data (velocity, direction, gusts) and storm wave generation was performed. Waves of more than 1–1.2 m height were accepted as a threshold for coastal storm waves (Boccotti, 2000). For the period 2010–2019, using data from the Kronshtadt meteorological station (https://rp5.ru) for the EGoF, storm events of more than 6 h duration with wind speed > 5 m/s were sufficient to produce storm waves of 1 – 1.2 m height (Ryabchuk et al. 2011) (Figure 10a). There was no significant rise in storm activity during this period and the maximal storm frequency of 30% occurred in 2019 with the average number of storm events in the EGoF being 16% per year.

For the 2010–2019 period, using data from the D6 platform station for the SE Baltic, storm events of more than 6 h duration with wind speed > 12 m / s were required to produce storm waves of more than 1–1.2 m height (Bobykina & Stont 2015; Figure 10b). In the SE Baltic in 2010–2019 there was no significant increase in the occurrence of storm events. The peak number of events over 10 years was observed in 2014 (2%). The average occurrence for intense events is 0.7% per year.

An increase in the frequency of strong storm events has been noted for both the SE Baltic Sea and theACCEPTED Gulf of Finland in recent decades MANUSCRIPT (Soomere et al. 2007; Ryabchuk et al. 2011a; Wolski et al. 2014; BACC Author Team 2015; Bobykina & Stont 2015). They occur up to four times per ten years for the EGoF, whilst in the second half of XX century such events occurred only once in 25 years (Barkov 1989). The impact of this increased storm activity on the coasts of the SE Baltic Sea is reflected in the destruction of coastal protection structures and flooding of inland territories due to foredune ridge erosion (Stont & Bobykina 2013; Danchenkov & Belov 2019; Danchenkov et al. 2019; Stont et al. 2019; Ryabchuk et al. 2011a). Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

According to VSEGEI monitoring observations, in the EGoF the most extreme erosion events are controlled by a specific combination of long-lasting western or south-western storms that bring high waves to the area in question, high water levels and an absence of stable sea ice during such events. Drastic reduction of beach material was observed after extreme erosion events in the Gulf of Finland (Eelsalu et al. 2015; Sergeev et al. 2018). Based on terrestrial laser scanning data to assess sand losses after storms, the depth of beach and foredune sediment was reduced by up to 0.9–1.2 m in a single autumn-winter storm event (Sergeev et al. 2018).

In the SE Baltic, wave activity is still the major driver of coastal processes (Kelpšaitė et al. 2011). The Sambia Peninsula has historically been considered as a source for bidirectional alongshore sediment flows (Harff et al. 2017). Most of the storms are associated with W– NW–N wind directions, the frequency of which is increasing (Kurennoy & Kelpsaite 2014) and for which the fetch length is maximum for this part of the sea. Wave heights in the shallow water along the cliffs of the Sambia Peninsula can reach significant values due to large bottom slopes (0.015 rad – 0.2 rad), compared with much lower angled slopes (0.005 rad) in the accumulation region of Pokrovskoye settlement where wave energy dissipation is much more significant. Thus steeper bottom slopes, caused by sediment deficits on the underwater coastal slope, lead to a greater energy content of storm waves. These, combined with the surge phenomena, intensively affect the shores of the Sambia Peninsula causing their erosion.

Nearshore sand mining, which took place in the nearshore in 1960s – 1990s, and damage of coastal dunes are the main negative technogenic factors of coastline evolution. In addition, construction of the St. Petersburg Flood Protection Facility (FPF) has been an important anthropogenic factor influencing coastal dynamics. Sea water level is a critical factor influencing the intensity of coastal erosion. The main aim of the FPF's function is to decrease the water level during floods within Neva Bay. Closing of the FPF gates prevents sea level increase within the Neva Bay during hazardous westerly cyclones, but at the same time the water level on the outer side of FPF (to the west of the construction) is higher than natural conditions. As a result, the FPF influence on coastal stability varies depending upon location. Inside Neva Bay is much better protected from erosion since the Facility started to operate in 2011. Outside the FPF the coastline experiences more severe wave impact associated with increased water-levels outside of the Facility during storm surges. In theACCEPTED EGoF the earliest coast protection measures,MANUSCRIPT aiming to stop erosion and protect sandy beaches, began at the end of the XIX century. Hard engineering structures, mostly groynes emplaced perpendicular to the shoreline and sea-walls, without sand nourishment were not effective due to the sediment deficit. Most of them are heavily damaged and have caused intensification of beach erosion with, in some instances, full loss of sand material both onland and offshore. As a consequence they have not protected the coast and, in fact, have reduced its recreation value. The first Coast Protection Plan, the „General Scheme of Coast Protection‟, for the most eastern part of the Gulf of Finland coasts was developed in the late 1980s but it was not realized. The only successful attempt of coast protection on this part of Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

the coast was an experimental beach nourishment in Komarovo village carried out in 1988 (Sergeev et al. 2018). By now the effect of that sand nourishment is depleted.

The first coastal protection structures along the Sambia Peninsula coast, mostly groynes perpendicular to the shoreline, were constructed before the Second World War. Their effectiveness has constantly decreased over time together with a growing sediment deficiency in the nearshore. Since the 1960s hard coastal protection constructions, seawalls, have been the main method of erosion minimization. These constructions have prevented some emergency situations in the coastal resorts, but at the same time they have initiated a sediment deficit that has decreased beach width and accelerated erosion of adjoining coastal segments.

Results generated in the frame of this presented study were recently incorporated into the Coast Protection plans of Kaliningrad Region and St. Petersburg City. Coasts of the Sambia Peninsula can be protected using complex engineering structures – sand nourishment with construction of artificial beaches to prevent storm impact on the escarpment base and compensate sediment deficit; wooden groynes perpendicular to shoreline to decrease the artificial beach erosion; gabions in the base of the coast escarpment and stabilization of its slope to prevent landslides. In 2016–2019 this complex of coast protection has started in the resort towns of Zelenorgadsk and Svetlogorsk in the frame of the development of the State Program of Kaliningrad Region.

In the EGoF in 2015–2016 the St. Petersburg City Marine Coast Protection Program was developed. This is based on both the Mater Plan of St. Petersburg city and the analyses of distribution of coastal erosion “hot spots”, erosion rates, coastal zone geology and morphology and existing coast protection constructions. The Program has identifed five areas of high priority for coastal protection within Kurortny District (to the west of FPF), two areas on the western coast of Kotlin Island and six areas within the Neva Bay. The key mode coastal protection here is also sand nourishment together with groynes or wave-breakers within the most heavily eroded and most valuable coastal segments. Unfortunately, realization of the Program has been postponed due to legislation and financial problems.

Conclusions

A comparative analysis of historical data, since 1936, and recent coastal monitoring measurements, for the last ten years, show an acceleration of coastal retreat of up to 1.4–1.6 m/yearACCEPTED in both Russian sectors of the Baltic MANUSCRIPT Sea. This activation of hazardous exogenous geological processes in coastal zones during the last decade is related to climatic changes and sediment deficits.

Combination of tectonic (vertical movement of the earth's crust), geological (geotechnical properties of coast forming deposits) and geomorphic factors controls the long-term coastal zone evolution. The coasts of the EGoF and coastal cliffs of the Russian SE Baltic are mainly formed of easily destructible clastic deposits of different grain-size (clay, silty sand, mixed sediments). Coastal erosion at the toe of the slope, coupled with surplus rainfall, numerous groundwater outlets and frost weathering are the main triggers of landslides. Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

Recently anthropogenic impact has become an important factor, both negatively and positively affecting coastline evolution, and comparable by its potency when compared with natural processes especially in the Kaliningrad Region.

The short-term, but most extreme erosion in the coastal zone is associated with long-duration storms combined with higher surge water levels. Such storms occur most frequently during the autumn-winter period and cause significant erosion where stable sea ice is absent. Recently the frequency of such storm events has increased due to climate warming.

Monitoring of the coastal geological processes and forecasting of the main trends of the Russian Baltic coast‟s evolution are very important to inform plans for coastal protection measures and to help ensure the future sustainable development of its coastal territories.

Acknowledgement

Article was prepared in frame of EMODnet–geology project. Analysis of the coastal dynamics of the Eastern Gulf of Finland was supported by the RSF project № 17–77–20041. Analysis of the coastal dynamics of the Kaliningrad area was done with a support of the state assignment of IO RAS (Theme No. 0149–2019–0013). We are cordially grateful to Reviewers for very useful and important comments and Cherith Moses for helping to improve the English of our manuscript.

References

Abromeit, J., Bock, P. & Jensch, A. 1900. Handbuch Des Deutschen Dünenbaues. Berlin. Aibulatov, N.A., Dolotov, Y.S., Orlova, G.A. & M.G., Y. 1966. Some features of flat sand coast dynamics [In Russian]. In: Investigations of Hydro- and Morphodynamic Processes of the Sea Coastal Zone. Moscow (Nauka), 38–103. Babakov, A.N. 2002. Spatiotemporal Structure of Coastal Currents and Sediment Transportation in the Coastal Zone of the South-Eastern Baltic Sea. AB IO RAS.

BACC Author Team, S. 2015. Second Assessment of Climate Change for the Baltic Sea Basin. The BACC II Author Team (ed.). Cham, Springer International Publishing, Regional Climate Studies, https://doi.org/10.1007/978-3-319-16006-1.

Barkov, L.. 1989. About lithodynamics of coastal zone and bottom of the eastern Gulf of Finland [In Russian]. Vestnik of the Leningrad University, 28, 25–32. Bass,ACCEPTED O.V. & Zhindarev, L.A.. 2007. Technogenesis MANUSCRIPT of sandy beaches coastal zones of enclosed seas. Geomorphology, 4, 17–24. Bobikina, V.P. & Karmanov, K.V. 2009. Coastal dynamics of the Gdansk Bay apex and connections with anthropogenic influence. In: Development of Artificial Territories in Coastal Zones of Seas, Lakes and Water Storage Reservoirs. Novosibirsk, Publisher of SB RAS, 119–124. Bobykina, V. & Boldyrev, V. 2008. Tendency in shore dynamics in the Kaliningrad Oblast according to five years monitoring information. In: Integrated Management, Sustainable Development Indicators, Spatial Planning and Monitoring of the South-Eastern Baltic Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

Coastal Regions. Kaliningrad, 46–47.

Bobykina, V.P. & Stont, Z.I. 2015. Winter storm activity in 2011–2012 and its consequences for the Southeastern Baltic coast. Water resources, 42, 371–377.

Boccotti, P. 2000. Wave Mechanics for Ocean Engineering. Elsevier Oceanography Series. Amsterdam, Elsevier Science. Boldyrev, V.L. & Ryabkova, O.I. 2001. Dynamics of coastal processes of the Kaliningrad region, Baltic Sea. Proceedings of the Russian Geographical Society, 133, 41–48. Boldyrev, V.L., Lashenkov, V.M. & Ryabkova, O.I. 1990. Storm deformation of coasts of the Kaliningrad region, Baltic Sea. Issues of coastal dynamics and paleogeography of the Baltic Sea coastal zone, 1, 97–129.

Dailidienė, I., Davulienė, L., Tilickis, B., Stankevičius, A. & Myrberg, K. 2006. Sea level variability at the Lithuanian coast of the Baltic Sea. Boreal Environment Research, 11, 109–121.

Danchenkov, A., Belov, N. & Stont, Z. 2019. Using the terrestrial laser scanning technique for aeolian sediment transport assessment in the coastal zone in seasonal scale. Estuarine, Coastal and Shelf Science, 223, 105–114.

Danchenkov, A.R. & Belov, N.S. 2019. Morphological changes in the beach-foredune system caused by a series of storms. Russ. J. Earth Sci, 19. Eelsalu, M., Soomere, T. & Julge, K. 2015. Quantification of changes in the beach volume by the application of an inverse of the Bruun Rule and laser scanning technology. Proceedings of the Estonian Academy of Sciences, 64, 240–248, https://doi.org/10.3176/proc.2015.3.06.

Gordeeva, S. & Malinin, V. 2014. Gulf of Finland Sea Level Variability. St. Petersburg, RSHU Publishers. Harff, J., Deng, J., et al. 2017. What Determines the Change of Coastlines in the Baltic Sea? In: Coastline Changes of the Baltic Sea from South to East. Springer, 15–35.

Information Bulletin on status of near-shore geological environment of Barents, White and Baltic Seas in 2013.Eds.: Petrov O.V., Lygin A.M. SPb, VSEGEI, 2014, 120 p. [In Russian].

Kahma, K., Pettersson, H. & Tuomi, L. 2003. Scatter diagram wave statistics from the northern Baltic Sea. MERI–Report Series of the Finnish Institute of Marine Research, 49ACCEPTED, 15–32. MANUSCRIPT

Kelpšaite, L., Herrmann, H. & Soomere, T. 2008. Wave regime differences along the eastern coast of the Baltic Proper. Proceedings of the Estonian Academy of Sciences, 57, 225– 231, https://doi.org/10.3176/proc.2008.4.04.

Kelpšaitė, L., Dailidienė, I. & Soomere, T. 2011. Changes in wave dynamics at the southeastern coast of the Baltic Proper during 1993–2008. Boreal Environment Research, 16, 220–232.

Kosyan, R., Krylenko, M., Ryabchuk, D. & Chubarenko, B. 2013. Russia. In: Pranzini, E. & Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

Williams, A. (eds) Coastal Erosion and Protection in Europe. London, Routledge, 19– 33. Kovaleva, O., Eelsalu, M. & Soomere, T. 2017. Hot-spots of large wave energy resources in relatively sheltered sections of the Baltic Sea coast. Renewable and Sustainable Energy Reviews, 74, https://doi.org/10.1016/j.rser.2017.02.033. Kurennoy, D. & Kelpsaite, L. 2014. Comparison of wind wave properties in Neva Bay and Curonian Lagoon based on modeled data. In: IEEE/OES Baltic International Symposium (BALTIC). 1–7. Leont‟ev, I.O., Ryabchuk, D.V., Sergeev, A.Y. & Sukhacheva, L.L. 2011. On the genesis of some bottom and coastal features in the Eastern Gulf of Finland. Oceanology, 51, 688– 698. Markov, K.K. 1931. Development of the Relief in the North-Western Part of the Leningrad District [In Russian]. Moscow-Leningrad.

Orviku, K. & Granö, O. 1992. Contemporary coasts. In: Raukas, A. & Hyvärinen, H. (eds) Geology of the Gulf of Finland. Tallinn, Valgus, 219–238. Petrov, O.V. (ed.). 2010. Atlas of Geological and Environmental Geological Maps of the Russian Area of the Baltic Sea. Saint Petersburg, Russia. Raukas, A. & Hyvärinen, H. (eds). 1992. Geology of the Gulf of Finland [In Russian]. Tallinn, Valgus.

Rózyński, G. 2010. Wave Climate in the Gulf of Gdańsk vs. Open Baltic Sea near Lubiatowo, Poland. Archives of Hydroengineering and Environmental Mechanics, 57, 167–176.

Ryabchenko, V.A., Leontyev, I.O., Ryabchuk, D. V., Sergeev, A.Y., Dvornikov, A.Y., Martyanov, S.D. & Zhamoida, V.A. 2018. Mitigation measures of coastal erosion on the Kotlin Island‟s shores in the Gulf of Finland, the Baltic Sea. Fundamentalnaya i Prikladnaya Gidrofizika, 11, 36–50.

Ryabchuk, D., Kolesov, A., Chubarenko, B., Spiridonov, M., Kurennoy, D. & Soomere, T. 2011a. Coastal erosion processes in the eastern Gulf of Finland and their links with geological and hydrometeorological factors. Boreal Environment Research, 16, 117– 137.

Ryabchuk, D., Leont‟yev, I., Sergeev, A., Nesterova, E., Sukhacheva, L. & Zhamoida, V. 2011b.ACCEPTED The morphology of sand spits andMANUSCRIPT the genesis of longshore sand waves on the coast of the eastern Gulf of Finland. Baltica, 24, 13–24.

Ryabchuk, D., Zhamoida, V., Sergeev, A., Kovaleva, O., Nesterova, E. & Budanov, L. 2014. The Coastal Erosion Map for Different Climate Change Scenarios. Compilation - Methodology and Results. Saint Petersburg.

Ryabchuk, D., Vallius, H., et al. 2017. Pollution history of Neva Bay bottom sediments (eastern Gulf of Finland, Baltic Sea). Baltica, 30, 31–46.

Ryabkova, O.I. 2000. Nature management and tasks of coastal protection in Kaliningrad Region shores [In Russian]. In: Physical Geography of the Ocean and Nature Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

Management at the Turn of XXI Century. Kaliningrad, 49–64.

Sergeev, A., Ryabchuk, D., Zhamoida, V., Leont‟yev, I., Kolesov, A., Kovaleva, O. & Orviku, K. 2018. Coastal dynamics of the eastern gulf of finland, the baltic sea: Toward a quantitative assessment. Baltica, 31, https://doi.org/10.5200/baltica.2018.31.05.

Šliaupa, S. & Hoth, P. 2011. Geological Evolution and Resources of the Baltic Sea Area from the Precambrian to the Quaternary. In: Harff, J. (ed.) The Baltic Sea Basin. 13–51.

Soloshchuk, P.V. 2010. Changes in the climate and ice conditions in the Gulf of Finland–the Neva Bay– the Neva river water system in the autumn-winter period in the past 15 years. Scientific notes of the Russian state hydrometeorological University, 14, 34–41. Soomere, T. 2008. Extremes and decadal variations of the northern Baltic Sea wave conditions. In: Extreme Ocean Waves. Springer, Dordrecht, 139–157., https://doi.org/https://doi.org/10.1007/978-1-4020-8314-3. Soomere, T., Kask, A., Kask, J. & Nerman, R. 2007. Transport and distribution of bottom sediments at Pirita Beach. Estonian Journal of Earth Sciences, 56, 233–254, https://doi.org/10.3176/earth.2007.04. Stont, Z. & Bobykina, V. 2013. About the winter storm activity of 2011 – 2012 and its implications for the Curonian Spit. Problems of studying and protecting the natural and cultural heritage of the “Curonian Spit” National park, 126–134. Stont, Z., Ulyanova, M., Krek, E., Churin, D., Gubareva & D. 2019. Storm activity during autumn-winter period of 2018-2019 in the Southeastern Baltic Sea. KSTU News, 53, 61– 71. Spiridonov, M., Ryabchuk, D., Zhamoida, V., Sergeev, A., Sivkov, V. & Boldyrev, V. 2011. Geological hazard potential at the Baltic Sea and its coastal zone: examples from the Eastern Gulf of Finland and the Kaliningrad Area. In: Harff, J., Björck, S. & Hoth, P. (eds) The Baltic Sea Basin. Springer-Verlag Berlin Heidelberg, 337–364., https://doi.org/10.1007/978-3-642-17220-5.

Tornquist, A. 1914. Die Wirkung der Sturmflüt vom 9 bis 10 Januar 1914 auf Samland und Nehrung. Schriften der Physikökonom. Gesellschaft, 245–246. Wichdorff, von H.H. 1919. Die Geologic Der Kurischen Nehrung Und Des Samlands, in Abhandl. Preuss. Geol. Landesanst.

Wolski, T., Wiśniewski, B., et al. 2014. Extreme sea levels at selected stations on the Baltic SeaACCEPTED coast. Oceanologia, 56, 259–290, MANUSCRIPThttps://doi.org/10.5697/oc.56-2.259. Yakovlev, S.A. 1925. Relief and Sediments of Leningrad Area [In Russian]. Zaitseva-Pärnaste, I., Soomere, T. & Tribštok, O. 2011. Spatial variations in the wave climate change in the Baltic Sea. Journal of Coastal Research, 195–199.

Zagorodnyh, V.A. & Kunaeva, N.A. 2005. Geology and mineral resources of Kaliningrad Region, Kaliningrad (Yantarny Skaz) [In Russian].

Zhamoida, V.A., Ryabchuk, D. V., Kropatchev, Y.P., Kurennoy, D., Boldyrev, V.L. & Sivkov, V. V. 2009. Recent sedimentation processes in the coastal zone of the Curonian Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

Spit (Kaliningrad region, Baltic Sea). Zeitschrift der Deutschen Gesellschaft für Geowissenschaften, 160, 143–157, https://doi.org/10.1127/1860-1804/2009/0160-0143. Zhindarev, L.A., Ryabkova, O.I. & Sivkov, V.V. 2012. Geology and geomorphology of sea coasts. In: Sivkov, V. V., Kadzhoyan, Y. S., Pichuzhkina, O. E. & Feldman, V. N. (eds) Oil and Environment of the Kaliningrad Region. Vol. II. The Sea. Kaliningrad, Terra Baltica, 19–36.

Figure captions Figure 1. А - Scheme of morphogenetic classification and coastal dynamics of the Eastern Gulf of Finland (EGoF). Measuring points – points of retrospective analyses of coastal escarpment and beach position according to remote sensing data (RSD) (rates in m/year); Relict uplifted Holocene marine terraces – terraces formed during maximum of Holocene transgressions (Ancylus Lake and Littorina Sea), covered mostly by sand; Coastal types – morphogenetic coastal types (legend in Table 1). B – location map of study area. FPF – St. Petersburg Flood Protection Facility. Figure 2. Areas of erosion and accumulation of Kotlin Island shoreline digitized from aerial photographs 15.08.1939 and satellite image of 2015 (Ryabchenko et al. 2018) with photos of coasts. Figure 3. Monitoring (2016–2019) coastal cross-section of southern coast of the EGoF in the vicinity of Lebyazhye village. A – cross-section description (2018) with samples position; B – aerial photo (by unmanned aerial vehicle); C – model of coastal relief with slope angles. Figure 4. Longshore sand waves and spit developing in the vicinity of the Bolshaya Izhora village. A – coastline transformation in 1990–2019 according to aerial photography and space image analyses. B – aerial image of eastern part of hooked spits. Figure 5. A – Scheme of morpho-genetic classification and coastal dynamics of Sambia Peninsula: 1–7 – Coastal types – morpho-genetic coastal types (legend in Table 2); 8 – measuring points of “Baltberegozaschita”; 9 – points of retrospective analyses of coastal escarpment and beach position according to RSD (rates of escarpment shift in m/year) with photos of coastal cliffs of Northern coast of Sambia Peninsula: a, b – landslides and erosion processes; c – glacial dislocations of quaternary deposits, d, e – panoramic view of geological structures of coastal cliffs of Svetlogorsk town: Q – Quaternary deposits; N – Neogene deposits; ₽ – Paleogene deposits. B – location map of study area. Figure 6. Monitoring (2016–2019) coastal cross-section of western coast of the Sambia Peninsula in the vicinity of the Donskoye village. A – representative cross-section description (2018) with samples position; B – aerial photo (by unmanned aerial vehicle); C – model of coastal relief with slope angles. FigureACCEPTED 7. Monitoring (2016–2019) coastal MANUSCRIPT cross-section of northern coast of Sambia Peninsula in the vicinity of Filino village. A – representative cross-section description (2018); B –aerial photo (by unmanned aerial vehicle); C – digital terrain model of the coast with slope angles. Figure 8. A– comparison of 1:25000 scale topographic map (1936) and high resolution space image (Bing Maps, 2013): 1 – coastal line; 2 – cliff edge. B – aerial photo of technogenic terrace in Pokrovskaya Bay (2019). Figure 9. 3D rendering of the frontal elevation of the surveying cliff at 2016 generated from over 7 million survey points (a); 3D rendering of the frontal elevation of the surveying cliff at 2017 generated from over 7 million survey points (b); DEM of difference between 2016 and Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

2017 surveys represents annual changes of volumes (c); Linear difference (m) of cliff crest positions obtained from TLS point cloud (d). Figure 10. Occurrence of storm events in a – Eastern Gulf of Finland; b – SE Baltic.

ACCEPTED MANUSCRIPT Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

Table 1. Parameters of coastal dynamics for different coastal types of the EGoF (based on Shepard classification (Shepard 1948)) Average rate Average rate of of cross-shore longshore coastal Legend dynamics (spits, Coastal type Description dynamics # sandwaves) (m/year) / (m/year)/ number of number of spits measurements 1 Skerries Primary coasts – drowned glacial erosion 0.05 / 2 0 coasts. Embayed coasts consisted of hard rocks 2 Sand accretion Primary coasts – river deposition coasts. 0.1 0 alluvial coast Coasts of deltas and estuaries 3 Moraine Primary coasts – glacial deposition coasts. -0.1 / 69 18 /2 (bouldery) erosion Coasts consisted of moraine deposits and coast with local developed following erosional processes pocket coarse- grained beaches 4 Erosion dominated Secondary coasts – wave erosion coasts. -0.25 / 43 47 /3 coast on Holocene Permanently straightening coasts consisted of marine terrace, soft Holocene deposits, erosional processes straightening are developed within marine palaeo-terraces 5 Erosion dominated Secondary coasts – wave erosion coasts. -0.5 / 4 30 / 1 coast on Holocene Straightening of coasts are finished, coasts marine terrace, consisted of soft Holocene deposits, erosional straightened processes are developed within marine palaeo-terraces 6 Sand accretion Secondary coasts – marine depositional 0.2 / 9 16 / 1 coasts coasts. Accumulative processes are dominated due to sediment inflow 7 Sand accretion Secondary coasts – marine depositional -0.7 / 5 14 / 4 coast with cuspate coasts. Movement of beach sand spits is foreland observed combining with accumulative processes 8 Technogenic (with No natural development of coasts due to - - hard coast technogenic impact (coast protection) protection structures)

ACCEPTED MANUSCRIPT Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

Table 2. Parameters of coastal dynamics for different coastal types of the South- Eastern Baltic (based on Shepard classification (Shepard 1948)) Rate of cliff dynamics Legend (m/year) / number of Coastal type Description # measurements for period 2008-2018 years 1 Active erosion cliff Secondary coasts – wave-straightened average -0.24; min 0.7; coasts. Active cliff is on the back of a max -1.1 / 26 beach 2 Active erosion cliff of Secondary coasts – wave-straightened average 0; min 0; landslide toe material coasts. max -0.1 / 8 3 Active erosion cliff Secondary coasts – wave-straightened average 0; min 0; max - with ravine erosion coasts. Ravine erosion as a main relief- 0.1 / 8 formed factor accelerates negative processes 4 Stable erosion cliff Secondary coasts – wave-straightened average -0.1; min 0; max - coasts. Stabilized cliff, no current 0.8 / 11 processes are observed 5 Eroded technogenic Secondary coasts – wave-straightened average -2.6; min 1.9; nourished coast coasts. Main input of material is max -8.2 / 12 initiated by the Amber Factory. 6 Progradating Secondary coasts – wave-straightened average -1.4; min -0.3; technogenic coasts. Accumulation of material on the max -2.9 / 7 nourished coast coasts is occurred by long-shore sediment transport from the northern part of the coast. 7 Hydroengineering Stable technogenic coast - facilities

ACCEPTED MANUSCRIPT Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

Table 3. Volume of yearly coastal cliff changes due to different processes Total Landslides Ravine Area, m2 5920 5111 809 Volume of changes, m3 -2426 -2213 -213 Volume of negative changes, m3 4751 4421 330 Volume of positive changes (redeposition), m3 2325 2208 117 Rate of annual negative changes, m3/m2 per year 0.76 0.75 0.77 Rate of annual changes, m3/m2 per year -0.5 -0.42 -0.68

ACCEPTED MANUSCRIPT Downloaded from http://qjegh.lyellcollection.org/ by guest on September 24, 2021

ACCEPTED MANUSCRIPT