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Knowledge of the coastal hydrodynamics, in particular the storm induced waves, is essential for management of the extremely vulnerable coastal environment. There, wave processes dominate surge, coastal currents, sediment transport and species distribution. Therefore, it is important to have a detailed insight into the exposure of different coastal areas to wave action. The study proposes a wave exposure classification of the Bulgarian Black Sea coast according to wave climate conditions as required by the Water Framework Directive (WFD), which focuses on ensuring good qualitative and quantitative state of water resources and ecosystems. To this end, the coast was divided into twenty-five coastal units while the applied methodology is based on numerical modelling of wave processes employing the third-generation SWAN wave model forced by wind fields spanning the period 2007-2018. The energy transport (power) of waves entering the coastal environment was estimated, which is considered an indicator for wave exposure. Furthermore, the study period is divided into two 6-year cycles, which allowed for capturing of the climatic wave fields alteration thus enabling to detect possible climate change effects. Spatial alteration of the energy transport maxima and, accordingly, wave exposure is reviewed. Results show that the northern most, middle and southern parts of the coast are the most exposed to wave action. The coastal orography, shore geographical orientation and beach slope depth have a foremost importance for the exposure type. When using the numerical modelling tools these factors are accounted for with the required level of accuracy. [ABSTRACT FROM AUTHOR]

The study presents results and discuss statistical properties of wind-generated sea waves measured in transitional waters of the Burgas Bay at the Bulgarian Black Sea. Wave measurements were acquired by Acoustic Doppler Current Profiler at two locations offshore Kraymorie and Chernomorets at water depths of approx. 15 m and 18 m, respectively. At each location, data were recorded for about three and a half months in winter seasons of 2021-2022 in front of Chernomorets and in 2022-2023 offshore Kraymorie, when storm activity intensifies posing higher risk of flooding, erosion and the threat to human activities along the coast. The study examines in statistical terms variability of significant wave height, peak wave period, mean wave direction and their interdependence. It also explores the storm activity during both periods of data collection in terms of wave height, storm duration and direction. Analysis includes clustering wave parameters as joint frequency of occurrence as percentage across predefined intervals to reveal their distribution in the time-span of measurements. [ABSTRACT FROM AUTHOR]

Since putting in operation of Chernomorets fishing port (Sozopol municipality, southern Bulgarian Black Sea coast) in January 2016, a number of negative effects have been observed in the area. The disturbance in the existing hydrodynamic balance led to intense coastal erosion and unwanted sand accumulation in the wave shadow area. Additionally, the coastal water quality has deteriorated in the port area. In order to undertake measures to mitigate the observed adverse effects, it is necessary to assess in detail the impact of the new facility on the hydrodynamic and morphodynamic regime in Chernomorets Bay. The assessment was done through geospatial morphological analysis based on satellite images, historical and present field observations, on one hand, and hydrodynamic and morphodynamic modelling, on the other one, which took into account the setting before and after the port construction. Typical seasonal wave conditions, related sea level variations, and a real storm situation based on field measurements during a storm surge event were simulated. The geospatial morphological analysis shows that there was a balance in the distribution of sandy material along the beach before the port construction. After the construction, a fast modification of the beach and bottom slope morphology has taken place resulting in ever increasing erosion in the north-western and western part of the bay and accumulation in the central and south-eastern one, accompanied by slope flattening. The modelling showed that the effect of the new port on the sediment dynamics is significant and completely irreversible in natural manner. This is due to the severely reduced natural system control on sediment fluxes balance. The presently observed beach erosion and coastal abrasion are expected to pursue, thus expanding the affected by both erosion and unwanted accumulation areas. [ABSTRACT FROM AUTHOR]

Water and sediments in coastal areas interact at different scales, thus shaping the marine environment and providing physical habitat for ecosystems. Hence, the hydromorphological conditions represent a key aspect of aquatic ecosystems considered in the Water Framework Directive as supporting quality elements (alongside the physicochemical), which are expected to provide the boundary conditions for the biological quality elements. Any alteration in those can reshape the corresponding biological conditions at various spatial and time scales. The Directive states that coastal waters might be subdivided considering significant changes in bathymetry, substrate, or exposure. Typologies established by the Directive should reflect the natural variability in hydromorphological characteristics and processes. Therefore, the aim of the present study is to establish the type-specific hydromorphological reference conditions by identifying areas within water bodies that are relatively homogeneous from a hydromorphological point of view in order to better serve both determination and management of environmental state and designation of highly modified coastal waters based on a set of clear quantitative criteria. The data employed comprise remote bathymetry measurements, sediment mapping and wave exposure type. These layers were geospatially analysed to differentiate aquatic areas of similar hydromorphological conditions. About 100 such areas were delineated, in which conditions could be considered reference. At the same time, analysis revealed eighteen modified smaller scale areas, within the above-mentioned ones, which are considered hotspots of hydromorphological change in anthropogenically modified environment; hence, an object of future monitoring and specific management actions. [ABSTRACT FROM AUTHOR]