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The longshore realignment of nearshore sandbars is a morphodynamic phenomenon of multiple sandbar systems that has been known about for several decades. However, it is unknown how switching-related nearshore changes influence the evolution of subaerial beaches. This study aims to define the relationship between sandbar switching episodes and the dynamic state of the beach-foredune system along the Curonian Spit coast (Baltic Sea) using decadal satellite-derived and beach profiling data. To define this connection, sandbar switching locations, sandbar cross-shore positions, shoreline positions, and sand volume changes in the beach-foredune system were assessed on interannual and storm-related time scales. Twenty-seven sandbar switching episodes were observed with an average duration of 14.3 months. Most of the switching episodes occurred at preferred locations, coinciding with breaking points of different shoreline orientations where oblique waves and longshore currents prevailed. Shoreline retreat at an average rate of –14.2 m was observed within most of the sandbar switching zones. During major storm events, the average rate of erosion within the sandbar switching zones was significantly higher than the rate outside them. On an interannual time scale, a moderate average rate of erosion was observed within the sandbar switching zones compared to a small accretion rate outside them. Additional case studies of coastal evolution within the switching zones indicated well-correlated rates of switching-determined outer sandbar positions, shoreline positions, and sand volume on the beach and foredune during the switching episodes. The results of this study could be important for the identification of erosional hot spots and coastal prediction.

Long-term observations of nearshore bar behaviour are a vital component of coastal monitoring, management, and prediction. Optical satellite remote sensing enables the possibility of such observations over large spatial areas, but its full potential remains unexploited. This study assessed alongshore variability in cross-shore nearshore bar behaviour on a wave-dominated multi-bar coast of the Curonian Spit (south-eastern Baltic Sea) between 2011 and 2021, using satellite-derived bar data. Nearshore bars were extracted from a time series of PlanetScope and RapidEye satellite images with an automated GIS-based algorithm, previously proposed by the study authors. The cross-shore behaviour of a multiple bar system was analysed by adapting traditional bathymetry-based analysis techniques to satellite-derived data that included bar crestlines and images of multi-scale Relative Bathymetric Position Index (RBPI). The analysis was performed on 1071 shore-perpendicular transects. Multi-bar onshore and offshore migration rates were quantified on interannual and seasonal timescales. The results show that, on an interannual timescale, bars migrated offshore at rates up to 9.7 m/month, while the rates of onshore migration reached up to 11 m/month. During the months of low wave energy, bars moved offshore at rates up to 6.2 m/month, and during the months of high wave energy, up to 12.9 m/month. However onshore migration rates, during the months of low and high wave energy, reached up to 7.0 and 13.4 m/month, respectively. A complex empirical orthogonal function (CEOF) analysis was performed on RBPI-derived cross-shore profiles, and cyclic offshore directed bar behaviour was examined. For the first time, the net offshore migration (NOM) cycle with bar cycle return periods of 1.8 to 13.5 years was investigated on the south-eastern Baltic Sea coast. Bar cycle return periods increased and rates of bar cross-shore migration decreased from north to south along the Curonian Spit. Similar nearshore bar behaviour regions were identified using clustering analysis based on quantified temporal and morphological characteristics of the bars. Factors controlling alongshore variability in bar cross-shore behaviour were determined. The study results suggest that small alongshore variations in nearshore hydrodynamics, caused by the local wave climate and its interplay with the shoreline orientation, determine the morphological and temporal variability of the multi-bar system in the Curonian Spit.

Satellite remote sensing is a valuable tool for coastal management, enabling the possibility to repeatedly observe nearshore sandbars. However, a lack of methodological approaches for sandbar detection prevents the wider use of satellite data in sandbar studies. In this paper, a novel fully automated approach to extract nearshore sandbars in high–medium-resolution satellite imagery using a GIS-based algorithm is proposed. The method is composed of a multi-step workflow providing a wide range of data with morphological nearshore characteristics, which include nearshore local relief, extracted sandbars, their crests and shoreline. The proposed processing chain involves a combination of spectral indices, ISODATA unsupervised classification, multi-scale Relative Bathymetric Position Index (RBPI), criteria-based selection operations, spatial statistics and filtering. The algorithm has been tested with 145 dates of PlanetScope and RapidEye imagery using a case study of the complex multiple sandbar system on the Curonian Spit coast, Baltic Sea. The comparison of results against 4 years of in situ bathymetric surveys shows a strong agreement between measured and derived sandbar crest positions (R2 = 0.999 and 0.997) with an average RMSE of 5.8 and 7 m for PlanetScope and RapidEye sensors, respectively. The accuracy of the proposed approach implies its feasibility to study inter-annual and seasonal sandbar behaviour and short-term changes related to high-impact events. Algorithm-provided outputs enable the possibility to evaluate a range of sandbar characteristics such as distance from shoreline, length, width, count or shape at a relevant spatiotemporal scale. The design of the method determines its compatibility with most sandbar morphologies and suitability to other sandy nearshores. Tests of the described technique with Sentinel-2 MSI and Landsat-8 OLI data show that it can be applied to publicly available medium resolution satellite imagery of other sensors.

Sandy coasts are one of the most dynamic spheres; continuously changing due to natural processes (severe weather and rising water levels) and human activities (coastal protection or port construction). Coastal geodynamic processes lead to beach sediment erosion or accumulation. The coast’s dynamic tendencies determine the changes in the volume of beach sediments; grain size; mineralogical; and geochemical composition of sediments. In addition to lithological and mineralogical analysis of sediments, geochemical analysis can provide valuable information about the local and regional patterns of sediment transport, distribution, provenance, and coasts’ conditions. The study aims to assess trace metals’ temporal and spatial distribution determined in the sandy beach sediments along the south-eastern Baltic Sea coast (Lithuania) during 2011–2018. The Lithuanian seacoast is divided into two parts: mainland and spit coast. Our results revealed that the dominant group of elements on the mainland includes Ca–Mg–Mn–Ti and on the Curonian Spit Fe–Pb–As–Co–Cr–Ni–Al, which remain unchanged during the years. The analysis included additional parameters such as beach volume, grain size and sorting, and heavy mineral concentration on the beach. The spatial analysis of trace elements indicated that the trace metal content depends on the coastal processes, but it differs in the mainland and spit sea coast. We identified a higher concentration of trace metals in the erosion-dominated areas in all analysed years on the mainland coast. On the spit coast, the trace metal concentration increased in areas associated with relict coarse sand and where the loading of sediments was active on the beach due to the northward along-shore transport.

Beach-foredune sediment exchange maintains a coastal system’s stability. Sea level fluctuation is one of the most important factors that modifies the beach and foredune sediment budget. This study aims to assess beach and foredune sand budget changes depending on sea level fluctuations. On the basis of annual measurements of cross-shore profiles on the Curonian Spit in Lithuania, the sediment volumes on the beach and foredune and their changes between 2002 and 2019 were calculated. The sea level fluctuations were examined in parallel. The obtained data revealed that in the case of a sand surplus, a relatively low sea level rise does not have a significant impact on the development of a foredune (and a minimal impact on a beach) on a decadal time-scale. Short-term sea level fluctuations are reflected in year-to-year variability in a beach sediment budget. However, no significant relationship between year-to-year variability in sea level fluctuation and the foredune sediment budget has yet been identified, nor is there a reliable year-to-year variability relationship between the foredune and beach sediment budget. The foredune sediment budget remained positive both through an increase and a reduction in the sediment volume on the beach.

An analysis of the dynamics of wind velocity along the Baltic coast of Lithuania is presented, based on data collected during field experiments in the summer, fall and winter of 1999–2001 and 2007–2009 at several sites (Būtingė, Šaipiai, Smiltynė, Juodkrantė, Pervalka and Nida). The locations were chosen in order to encompass a wide spectrum of beach and dune ridge morphology. The relationship between wind velocity dynamics and coastal morphology was established, based on measurements of the slope angle, height and shape of the dune crest, as well as measurements of the morphology of the area behind the foredune ridge. On the basis of a comparison of near-surface wind velocity patterns, shear velocity (U*) and surface roughness length (z0) were calculated. It was determined that U* decreases from the middle of the beach towards the foredune toe, then increases towards the crest of the foredune and decreases down the lee slope. A direct correlation exists between U* and the stoss slope inclination, and the relative height of the foredune. Surface roughness length also increases from the beach towards the foredune crest.

As the safe depth for navigation is no longer ensured due to intense accumulation of sediments in the avanport of the old port, which was constructed in 1923–1940, reconstruction of Šventoji port jetties was planned, which should commence in 2013. The assessment of impact of Šventoji port jetties was done on the nearby coasts, based on analysis of the 20th and 21st century cartographic material as well as monitoring data on coastal dynamics. The old port construction caused the formation of the accumulative cape; the area of which has grown to 44.90 ha. The coastline erosion processes have become especially intense northwards from the formed cape to the Latvian border. Approx. 38.41 ha area of land has been washed-out in the section. During the last 17 years, the southern jetty has become more and more pervious to sediments. Sediment volume stabilization occurred on the northern side of the jetty, and accumulation tendency was in the southern part of the port. Results of sediment transport modelling with MIKE 21 confirm that the reconstruction of Šventoji port according to alternative “1” (length of jetties – 400 m) answers the minimal requirements of port and makes the least impact for the hydrodynamic and lithodynamic processes in the Baltic Sea nearshore. The reconstruction of port according to alternative “2” (length of jetties – 800 m) will cause the intensive changes of the Baltic Sea coastline dynamics in adjacent regions. First published online: 14 Dec 2012

During the reconstruction of 2001–2002, the Klaipėda port jetties were lengthened (the northern jetty by 205 m and the southern by 278 m). These works produced an impact on dynamic coastal processes in the neighbourhood of the port. The evaluation of the impact of jetties reconstruction was based on the data obtained in 1995–2010 during the monitoring of coastal dynamics in the port of Klaipėda. Study area includes 10 km coastal strip of mainland and 12 km coastal strip of Curonian Spit. The analysis of the data concerning the changes in the annual amount of coastal sediment served as a basis to evaluate the impact of Klaipėda port jetties on the trends in coastal dynamics prevailing before the reconstruction and their changes after it. It was found that in the mainland coastal stretch closest to the jetties, where in the last decade before jetties extension the seashore was relatively stable, the coastal erosion trends were dominant. Meanwhile, the closest to the jetties coastal stretch of the Curonion Spit, where erosion processes dominated in the last decade before jetties extension, stabilized right after the reconstruction and with a passage of time sediment accumulation trends have become prevailing. Santrauka 2001–2002 m. vykdant Klaipėdos jūrų uosto rekonstrukcijos darbus buvo prailginti molai (šiaurinis 205 m, pietinis – 278 m). Vertinant molų rekonstrukcijos įtaką jūros krantų greta uosto dinamikai remtasi nuo 1995 m. atliekamos jos stebėsenos duomenimis. Tyrimų rajonas apėmė 10 km ilgio žemyno kranto juostą ir 12 km ilgio Kuršių nerijos kranto juostą. Matavimai buvo atliekami 18 profilių žemyno krante ir 12 profilių Kuršių nerijos krante. Analizuojant kasmetinės kranto sąnašų kiekio kaitos duomenis įvertinta Klaipėdos uosto molų įtaka gretimų krantų dinamikos tendencijoms, vyravusioms iki molų rekonstrukcijos, ir jų pokyčiams po molų rekonstrukcijos. Nustatyta, kad žemyne, arčiausiai molų esančioje kranto atkarpoje, kurioje pastarąjį dešimtmetį iki uosto molų prailginimo krantas buvo santykinai stabilus, po rekonstrukcijos įsivyravo kranto ardos tendencijos. Kuršių nerijos krante, kur pastarąjį dešimtmetį iki molų prailginimo arčiausioje nuo molo kranto atkarpoje vyravo intensyviõs ardos procesai, po molų rekonstrukcijos krantas iš pradžių stabilizavosi, o vėliau čia pradėjo vyrauti sąnašų akumuliacijos tendencijos. Reikšminiai žodžiai: aplinkos stebėsena, Klaipėdos uostas, molai, kranto sąnašos, įplaukos kanalo pagilinimas

An intensive abrasion of the coast of the most popular Lithuanian Palanga health‐resort necessitates consideration of the most effective ways of its stabilization. Based on the data of field investigations and literary sources, the possibilities of Palanga coastal zone regeneration using the sand dredged from the entrance channel of Klaipeda port are considered. Based on the current geodynamic trends of Palanga coastal zone and results obtained by comparative analysis of granulometric composition of sediments dredged from the entrance channel of Klaipeda Port, the optimal possibilities of using the dredged sand for coast regeneration were determined. It was established that formation of underwater sandbar (analogue of natural bar) in the surf zone of coastal sector between the Palanga Pier and Birute Mount at a depth of 3 m would be the best solution for coast regeneration under the current conditions. Santrauka Intensyvi populiariausio Lietuvoje Palangos kurorto jūros kranto arda verčia ieškoti efektyviu kranto stabilizavimo metodu. Pastaruoju metu (2003–2008 m.) atlikti apsauginio paplūdimio kopagūbrio tvirtinimo bei paplūdimio sanašu atsargu papildymo Palangos rekreacineje zonoje darbai leme tik trumpalaiki kranto apsaugos efekta. Straipsnyje, remiantis natūriniu tyrimu bei literatūros duomenimis, ivertintos smelio, iškasamo iš Klaipedos iplaukos kanalo, naudojimo Palangos kranto zonai regeneruoti galimybes. Atsižvelgus i dabartines Palangos kranto zonos geodinamines tendencijas bei atlikus šio ruožo ir iškasamo iš Klaipedos uosto iplaukos kanalo biriu sanašu sudeties lyginamaja analize, nustatytos optimalios iškasamo smelio panaudojimo kranto zonai regeneruoti galimybes. Esant dabartinei situacijai efektyviausias kranto zonos regeneravimo būdas ‐ povandeninio volo (gamtinio sekliaus analogo) 3 m gylyje kranto ruožo tarp Palangos tilto ir Birutes kalno gožos zonoje formavimas. Резюме Интенсивный размыв морского берега в рекреационной зоне самого популярного курорта Литвы – Палангe вынуждает искать эффективные способы его стабилизации. Выполненные за последнее время (2003–2008 гг.) работы по укреплению дюнного вала и попытка пополнить пляж наносами в береговой зоне г. Паланги дали лишь кратковременный берегозащитный эффект. На основе натурных данных в статье оценены возможности использования для регенерации береговой зоны Паланги песка, выкапываемого из подвходного канала порта Клайпеды. Учитывая полученные результаты исследований современных геодинамических тенденций береговой зоны г. Паланги, состав наносов подвходного канала порта г. Клайпеды и изучаемого участка, установлены оптимальные возможности использования добываемого песка для стабилизации береговой зоны г. Паланги. Установлено, что при нынешней ситуации самым эффективным способом регенерации береговой зоны является формирование подводного вала (аналог природного) в прибойной зоне на глубине 3 метров на участке между Палангским мостом и мысом горы Бируте. First Publish Online: 21 Jun 2011 Reikšminiai žodžiai: kranto zonos sąnašų papildymas, dirbtinis sėklius, sąnašų granuliometrinė sudėtis. Ключевые слова: подпитка береговой зоны, искусственный подводный вал, гранулометрический состав наносов.