Modeling of the coastal zone relief and granulometric composition changes of sediments in the region of the Bogaily Lake bay-bar (the Western Crimea) during storm

Introduction . A series of numerical experiments was carried out to study the mechanism of storm deformations of the coastal zone relief and the redistribution of different sediment fractions after the parameters of the wind waves directed almost normally to the coastline, are changed. Data and methods . The lithodynamic processes taking place at the Western Crimea coastal zone in the region of the Lake Bogaily bay-bar were investigated using the XBeach mathematical model. The in-situ data on the bottom relief and the sediments granulometric composition obtained during moni-toring observations in the Western Crimea coastal zone performed by the Marine Hydrophysical Institute of RAS was used as the model input parameters. The granulometric composition was preset as a mixture of three components distributed along the profile of the underwater coastal slope; at that the ratios of volume concentrations were different. Results . It is shown that influence of the storm waves results in intensive beach erosion, strong altera-tion of the profile of the underwater coastal slope upper part and formation of an accumulative body. Main changes of the initial profile and redistribution of the sediment fractions are observed during the first 3–6 hours and depend on the wave period. The rate of the water edge retreat and the values of the coastal zone relief deformation were quantitatively assessed for various time periods of the wave action. Position of the marine boundary of the site within which significant motion of sediments and their accumulation during a storm took place was calculated. Discussion and conclusion . Possibility of the bay-bar crest erosion is analyzed for the wind wave’ different periods. It is shown that the volume concentrations of different components of the mixture change mainly after the fine fractions are rapidly removed to the seaward part of the bottom profile and the coarser fractions are redistributed in the upper part of the underwater coastal slope. The obtained results provide a possibility of indirect determining the conditions for blocking the alongshore sediments transport in case of building a hydraulic structure.