Mathematical Modeling the Dynamics of the Bottom Sediments Granulometric Composition in the Balaklava Bay Affected by the Wind Waves

Abstract

Purpose. Based on the mathematical modeling methods, influence of the wind waves on redistribution of the sand fractions in the semi-closed estuary-type water area is estimated using the Balaklava Bay as an example. Methods and Results. A two-dimensional version of the XBeach model with a constant grid spacing 10 m was used. The characteristics of wind waves were preset using the JONSWAP spectrum. The calculations were carried out for a storm event lasting about 12 hours once a year. The in-situ data on the particle size distribution in the bottom sediments resulted from the monitoring observations in the Balaklava Bay region was used in the numerical experiments. Conclusions. The results of modeling showed that the basic determining factors regulating the sediments movement were the depth and the bottom slope. It is noted that changing of the bottom inclination angle between the isobaths 6–7 and 7–8 m leads to deposition of the large and medium fractions, and in the area between the isobaths 9–10 and 10–12 m – to accumulation of fine sand. It was revealed that in the Balaklava Bay water area, the main redistribution of sand material caused by the storm waves took place within the southern basin, as well as at the bay exit in the coastal zone of the Megalo-Yalo Gulf. This is primarily determined by the features of the Balaklava Bay coast orography, namely, the knee-shaped narrowness separating the northern and southern basins. Nevertheless, in the isolated northern part of the Balaklava Bay being affected by the storm waves, insignificant dynamics of sand material was observed. The fractions of bottom sediments are redistributed from the western coast to the central part of the basin and to the eastern coast of the bay.