No abstract

The paper describes lithodynamic and morphodynamic processes occurring in the main part of the south-eastern Baltic coastal area, namely on the sea shores from the Vistula mouth in the Gulf of Gdansk to the Lithuanian-Latvian border. The study area is subject to intensive natural coastal changes, as well as shore evolution caused by anthropogenic impacts at several locations. Methods of coastal protection against erosion and shore stabilization systems applied in the past and currently are described. The paper deals with the causes of the dynamics of beach/dune shores and cliffs. It presents the authors’ field observations of 2010-2013, as well as previously gained knowledge and the results of Polish, Russian and joint Polish-Russian field surveys.

A review of morphological and morphodynamic studies of the coast of the Kaliningrad oblast has been carried out for half a century. The studies include monitoring measurements by the Atlantic Branch of the Shirshov Institute of Oceanology of the Russian Academy of Sciences (AB IO RAS) with the participation of the state institute Baltberegozashchita (BBZ), as well as pre-war studies and cartographic analyses of long-term coastline migration carried out by the private company Baltic Aerogeodetic Enterprise (BaltAGE). It shows the spatial alternation of abrasive and accumulative areas, as well as frequent changes in beach width and height within the same morphological coast type. A change in the development trend of particular coast sections from year to year was noted. The significant influence of anthropogenic factors on the coastal development was emphasized, including changes in the direction of coastal retreat/advance along an extensive coastal stretch. Comparison of the interannual and nearly century-old dynamics of the coast revealed noticeable differences between them, with opposite trends in several large-scale coast sections.

The published schemes of the net alongshore sediment transport near the eastern coast of Gdansk Bay have been systematized. Considerable discrepancies have been identified in the structure and localization of the convergence zones of opposite currents. The results of station-based measurements of bottom currents near the Strait of Baltiysk at depths of 6-16 m were used to show that, at winds >6 m/s, the alongshore currents run along the alongshore wind component. The morphodynamic accumulation (filling of the entry corner and abrasion in the shadow zone of the obstacle) and abrasion (orientation of the abrasion depression at the extreme end of the harbor moles) criteria are discussed. The abrasion criterion is shown to work better than the accumulation criterion in determining the net sediment transport in the coastal reaches with a normal or near-normal approach angle of the wave energy flow toward the shore. The specific features of the mechanism of sediment transport from south to north, by-passing Baltiisk harbor moles, from the abrasion to accumulation shore segments are given. Two schemes of the opposite Vistula and Sambian alongshore sediment flows are proposed: before the construction of the entry harbor moles in the Baltic Strait with a vast migration zone near the northern end of the Vistula Spit and after the construction of these moles, which has narrowed this zone and shifted its southern boundary northward toward the moles.