Analytical studies of the dynamics of pocket beach

Abstract

The beach site is located in the utmost northeastern part of the Nevskaya Bay. A boulder dam is built on the western side, which, however, fails to protect the beach from the effects of waves that cause longshore sediment transport. The planned construction of transverse beach–retaining structures outlines in the “Water Sports Base in Primorsky District” initiative, mightchange the current situation. This study objective is to predict the evolution of the coastal contour resulting from the planned construction in the next few decades. A natural analogue of such an artificial structure could be a pocket beach located between two natural promontories. The sediment equilibrium at this study location includes three main components: volumes of erosion, accumulation and bypassing. The results include the computed wave patterns and the movement of sediment along the shoreline. The lateral sediment transport diminishes notably over time, driven by the alteration of the shoreline contour and the reduction in the angle between the wave equilibrium and the coastal resultant. The erosion and accumulation volumes increase over time, but their rates slow down. The shoreline displacement becomes more prominent over time; however, the rates of erosion differ from accumulation. The shoreline is moving particularly fast in the first years after construction, and then the process slows down gradually. The introduction of artificial beach protection structures in the 300th Anniversary Park of St. Petersburg will considerably reduce both the pace of beach erosion and the affected area. However, the erosion process will not be completely halted.