189 since 1961 BALTICA Volume 28 Number 2 December 2015: 189–199 doi: 10.5200/baltica.2015.28.16 Dynamics of sediments disposed in the marine coastal zone near the Vistula Lagoon inlet, south-eastern part of the Baltic Sea Vladimir Chechko, Andrei Sokolov, Boris Chubarenko, Dmitrii Dikii, Victoriya Topchaya Chechko, V., Sokolov, A., Chubarenko, B., Dikii, D., Topchaya, V., 2015. Dynamics of sediments disposed in the marine coastal zone near the Vistula Lagoon inlet, south-eastern part of the Baltic Sea. Baltica 28 (2), 189–199. Vilnius. ISSN 0067-3064. Manuscript submitted 01 November 2015 / Accepted 27 November 2015 / Published online 10 December 2015 © Baltica 2015 Abstract The article discusses the possibility of protecting the shore by disposing of dredged material at shallow depths. An example of a permanently eroded open marine shore segment located south of the Vistula Lagoon inlet (south-eastern part of the Baltic Sea) is considered. This shore segment is permanently caused by downstream erosion due to the moles bordering the entrance to the Vistula Lagoon (Baltiysk Strait) and interrupting longshore sediment transport. Changes of sediment distribution resulting from a demonstration disposal of clean fne sand at depths of seven to nine metres opposite the eroded segment of the shore are ex- amined. A supplementary numerical modelling analysis of sediment transport for different winds showed that the disposed material is transported northward or southward alongshore depending on the wind direction, and almost none of it is stored at the shore slope. The demonstration disposal and numerical modelling results dem- onstrate that the only way to use the dredged material to protect the eroded shore near the inlet of the Vistula Lagoon is to dispose it directly onto the beach and not into the shallow water nearby. Keywords • coastal erosion • bottom sediments • disposal • dredged material • sediment transport • numerical modelling Vladimir Chechko [che-chko@mail.ru], Dmitrii Dikii, Victoriya Topchaya, P. P. Shirshov Institute of Oceanology of Russian Academy of Sciences, Atlantic Branch, Prospect Mira, 1, 236022, Kaliningrad, Russia; Andrei Sokolov, Boris Chubarenko, Immanuel Kant Baltic Federal University, Al. Nevskogo Str., 14, 236041, Kaliningrad, Russia INTRODUCTION Nearly all entrance moles for ports and channels in the southern and eastern parts of the Baltic Sea nega- tively infuence the sediment dynamics along the adjacent coastline (Aibulatov, Bass 1983; Boldyrev 1988; Gudelis 1988; Basinski, Zmudzinski 1988). It is a common phenomenon that construction of hy- drotechnical facilities along an open sea shore is usu- ally followed by coastal erosion (Walker 1988; Pran- zini, Williams 2013). Entrance moles at the inlet to the Vistula Lagoon (the south-eastern part of the BalticSea) constructed at the end of the 18th century became an obstacle (Fig. 1) to the longshore sediment transport from the north to the south; consequently, the downstream coastal ero- sion began at the shore segment immediately south of the moles. The average erosion rate at the 2.5–3 km segment of the Vistula Spit south of the moles is currently 0.7–5.5 m a year but may reach 8 m a year (Boinagryan 1966; Bass, Zhindarev 2004; Bobykina 2007). Such long-lasting permanent erosion results in a real threat of fooding for the Kosa village located south of the Baltiysk Strait (Chechko et al. 2008). The southward sediment fux moves alongshore around the moles at a greater depth. In addition some of the sediments enter the Baltiysk Strait during infow of coastal waters into the Vistula Lagoon caused by western winds (Chechko et al. 2008). The incoming suspended material settles down forming a reversed bar immediately within the Vistula Lagoon (Chu- barenko, Margonski 2008), and reduces the depth of