Variation of sedimentation rate in the semi-enclosed bay determined by ¹³⁷Cs distribution in sediment (Kaštela Bay, Croatia)

Purpose of this research was to study the rate at which the semi-enclosed bay such as the Kaštela Bay reacts to the coastal processes of industrialization and urbanization, the extent of the influence of human activities on the bay, and the sediment distribution affected by anthropogenic influence. Temporal and spatial sedimentation rate variations were observed between three studied periods: 1954–2005, 1963–2005/2006, and 1986–2005/2006. Sedimentation rates were in the following ranges: 0.29–0.49 cm/yr for the 1954–2005 period, 0.58–0.95 cm/yr for the 1963–2005/2006 period, and 0.50–1.32 cm/yr for the 1986–2005/2006 period. The average total sedimentation rates for three periods were 0.41 cm/yr, 0.81 cm/yr, and 0.61 cm/yr, respectively. Sedimentation rate for the individual 1963–1986 period marked with two ¹³⁷Cs marker peaks was in the 0.65–1.30 cm/yr range, while the mean value was 1.06 cm/yr. Long-term sedimentation rate increase in the whole Kaštela Bay was observed and clearly connected to the industrialization and urbanization processes in the coastal area. These processes reflect very quickly, in terms of years, in the sedimentation rates. Intensive anthropogenic activities in the coastal area are reflected in the whole bay depending on the amount of the discharged sediment material, topography of the sea bottom, and water currents. Some localized areas of sediment accumulation may form. - Highlights: • Long-term sedimentation rate increase in the whole bay since the 1950s. • Sedimentation rate increased due to urbanization and industrialization. • Temporal and spatial sedimentation rate variability observed.