Modeling the interaction of artificial reefs with a wave field (case study: Odessa coast)

Abstract

One of the prospective areas of today’s marine and oceanic resource management is creation of artificial reefs. Artificial reefs do not represent a universal solution to environmental problems of water areas; their creation serves as a comprehensive flexible approach to restoration of aquatic ecosystems. Natural conditions and species composition of aquatic organisms in the North-Western part of the Black Sea significantly differ from conditions in the World Ocean area, where artificial reefs are traditionally built and used. This article presents generalized results of experiments featuring creation of artificial reefs in natural regional conditions of the Odessa coast in the 20th century. The international experience in creating artificial reefs with preset properties was analyzed, and peculiarities of applying mathematical modeling of wave processes when designing artificial reefs were reviewed. One of the prospective areas is to create combined-purpose artificial reefs on the Odesa coast: an alternative option of reconstructing and repairing hydraulic engineering structures; coast protection structures suitable for population with aquatic organisms and capable of producing alluviums and debris for nourishment of the coastal area. The interaction of three artificial reef variants with a wind wave field was studied. The modeling was done using a third-generation SWAN wave model, version 41.10. The model’s input parameters included: design parameters of waves in hazardous wave directions 4% occurrence in regime, a digital model of the submarine relief, the depth of location and geometric parameters of artificial reefs. The modeling has revealed that the analyzed artificial reef variants perform the wave protection function. Depending on the ratio between the depth and geometric location, wave protection functions could be performed not only by individual structures but by their entirety: a reef complex. A decrease in the wave height by 0.1–0.2 m was observed in the place where the structures are located. Benthal orbital wave speed is the highest on the wave crest, and low at the distance of 0.25 of the length of an oncoming storm wave from the structure. With these figures, the material of crests with the fineness of 10–20 mm and the bottom of artificial reefs with the fineness of 4–10 mm will not be eroded.