Geographia Technica, Vol 13, Issue no. 1/2018, pp. 62-72
ASSESSMENT OF EFFECTIVENESS OF COASTAL PROTECTION STRUCTURES FOR ENSURING A CONSTANT LAGOON-SEA WATER EXCHANGE IN THE NORTH-WESTERN BLACK SEA REGION
Dmytro KUSHNIR, Yuri TUCHKOVENKO
ABSTRACT: Coastal lagoons of the Northern-Western Black Sea region show a long-term tendency in decreasing their water volume while increasing in water salinity as well as in nutrient and pollutant concentration. This occurs due to a limited connection between the lagoons and the sea, on the one hand, and the significant negative freshwater balance, on the other hand. To compensate this, a constant multi-directional water exchange with the sea through connecting canals is needed for the lagoons. However, the connecting canals require marine engineering, ensuring the protection from the sand deposition at their sea parts, in order to guarantee a year-round bidirectional ‘sea-lagoon’ water exchange. In the present work, a case study has been implemented to the Tylihulskyi Lyman lagoon, for which the existing canal has been reconstructed. A coupled numerical model for currents, waves and sediment transport has been used to estimate the efficiency of various engineering options 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 pattern with maximum sediment transport has been simulated. Four variants of the engineering design of hydroengineering structure for wave and sediment protection were considered. Results have shown that the optimal solution for 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.
Keywords: North-Western Black Sea Region, lagoons, canals, sediment deposition, modelling.
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