The Impact of the Sopot Pier Marina on the Local Surf Zone

Abstract

An accelerated accumulation of sand in the area of the Sopot Pier Marina has been observed since 2010. The beach near the pier has grown by several meters and local depths have been decreasing. Before construction of the marina, spit type shoreline form had sometimes formed. But it has never begun to grow in the way it has grown after 2010, as a result of disturbed sediment transport in the local surf zone. The main goal of this work is to estimate where this process is going on. To assess the influence of the marina on the longshore drift, geometrical analysis of the existing marina has been performed and numerical model of sediment transport has been implemented. A simple analysis of the Sopot Pier dimensions suggests that the final form of growing spit will be tombolo. For the purpose of having an additional point of view, a numerical model of sediment transport based on MIKE by DHI product has been developed. The model results show that the Sopot Pier Marina has a strong influence on the sediment transport by generating a wave shadow zone. Consequently, it disturbs the continuity of sediment transport along the beach, which as a result impacts the costal line. The model indicates that 80% of this sand was transported from the area located southeast of the Sopot Pier, whereas the remaining 20% from the northwest area. Simulations showed that accumulated sand came from local surf zone and beaches. This result has been confirmed by bathymetry measurements performed by the Maritime Office in Gdynia.