Estimation of Effectiveness of Hydroengineering Structures for Ensuring a Constant Connection of Lagoons of the North-Western Black Sea Region with the Sea

Abstract

The majority of coastal lagoons, situated in the Ukrainian North-Western Black Sea region, show a long-term tendency of water volume decrease and the increase in water salinity and concentration of nutrients and pollutants due to continuing lack of the conjunction with the sea and significant deficiency in the annual freshwater balance. To compensate this, a constant multi-directional water exchange with the sea through connecting canals is needed for the lagoons. The connecting canals need to be protected from shoaling, caused by the deposition of sand on their sea parts, for ensuring a year-round bidirectional ‘sea-lagoon’ water exchange. A set of coupled numerical models for currents, waves and the sediment transport was used to estimate the efficiency of different variants of the engineering design of hydroengineering protective structure, which is being constructed at the sea part of the restored artificial canal, connecting the Tylihulskyi Lyman Lagoon with the Black Sea. A real storm situation was simulated, under which the transport of sediments reaches its maximum. Four variants of the engineering design of hydroengineering structure for wave and sediment protection were considered. It was found that the most effective embodiment of the hydroengineering structure is the variant comprised of parabolic-shaped groynes and the underwater breakwater. Reduction in the intake of sediments into the canal is achieved by sedimentation at the entrance to the protective structure. Therefore, under a long-term operation of the ‘sea-lagoon’ connecting canal, measures for removing the depositions accumulated in the inner sections of the protective structure should be implemented. The results of this study can be generalized to other lagoons of the Azov-Black Sea basin.