Accounting for the Local Wave and Morphodynamic Processes in Coastal Hydraulic Engineering

Purpose. Estimates of wave parameters in the coastal waters are of great practical importance for designing and operating coastal infrastructure facilities. On the example of the Saki bay-bar region (Western Crimea), the experience of studying the wave and morphodynamic processes in the coastal zone is presented being applied to the tasks of designing and building protective hydraulic structures. Methods and Results. Mathematical modeling of the wave and morphodynamic processes in the area under study was done using the following: spectral model of the wind waves SWAN, hydrodynamic model SWASH, complex morphodynamic model XBeach and integral model of the coastal zone evolution GenCade. The wave regime was analyzed using the 41-year time series (1979–2019) of wave parameters resulted from the retrospective calculations of wind waves based on the SWAN model and the ERA atmospheric reanalysis data. The operational and extreme characteristics of wind waves were obtained. The spatial structure of the wave fields for different types of wind effects was modeled. The most intense waves are shown to occur during the southwest wind. The height and length of wave run-up on the coast and the coastal zone profile deformations for the storms of different durations were estimated. The values of the total annual along-coastal sediment flow in the design area were obtained for 1979–2019. In 70% of the cases, the sediment flow was established to be directed towards the Evpatoriya coast. Conclusions. The studies have shown that neglecting scientifically based recommendations when designing coastal infrastructure facilities can lead both to disruption of the existing system of the coastal zone natural formation, and to significant negative consequences for the coastline of almost 10 km length. These consequences can be manifested in a reduction of the beach zone width, a decrease in elevation marks, and replacement of sand with the pebble-gravel fractions in some areas that worsen recreational features of the beaches. Having been analyzed and taken into account, the planned location of the base of the enclosing wall shows that in some parts, the embankment wall can be possibly washed away and damaged. These conclusions were confirmed in practice already during the facility construction. Based on the results of the performed study, the constructions contributing significantly to the changes in the coastal zone morphodynamics were recommended for exclusion from the project

Morphodynamics of Sevastopol Bays under Anthropogenic Impact

The degradation of the Crimean shores under the influence of the anthropogenic factor has become a serious problem to overcome which significant efforts and financial resources are spent. The purpose of the article is to consider retrospectively the morphodynamics of Sevastopol bays under the influence of anthropogenic activity. We used materials of MHI RAS observations, satellite and aerial photographs, literary sources as well as a range of maps and plans, mainly of the 19th century. It is shown that the natural environment of Sevastopol bays has changed significantly as a result of anthropogenic activity. The greatest impact is noted in the area of Sevastopol Bay, where the shores have been subjected to significant anthropogenic impact (the removal of cliffs, concreting of the coastline, construction of piers, etc.). The shores, which can be classified as untransformed, have survived only on 1.1 km (or 3 %) of the original length of the coastline. The outer shores of the coastal bays have preserved their natural state to the greatest extent. Only 1.3 km (17 %) were subject to anthropogenic impact consisting in cutting and planning of cliffs and erection of coastal protection and beach-retaining structures. The shores of the coastal bays themselves were subject to a much greater impact. Only one of them preserves the average level of technogenic impact, whereas in three of them it is the maximum, and in three others it is extreme. Out of 33.5 km of the inner perimeter of the bays, about 10 km (30 %) remain relatively unchanged. It is noted that by now only 0.3 km or 10 % of the pre-existing shores with sandy beaches have remained in the region under consideration. It is observed that as a result of anthropogenic activity, the Sevastopol group of salt lakes, which were previously used medicinally, has been almost destroyed

Quasi-Periodicity of the Black Sea Wind Spatial-Temporal Variability and Its Relation with the North Atlantic Oscillation phases

Quasi-periodic features of the inter-annual and inter-decadal spatial-temporal variability of the wind speed absolute value (W) in the Black Sea area are assessed based on a series of 60–100-year-long direct observations performed at eight coastal stations, and also on the reanalysis data obtained from the NDP-048, WDC, NCDC, NCEP/NCAR (1948–2011) and MERRA (1980–2015) arrays. Three groups of oscillations with the periods T about 60–90, 20–40 and 3–15 years that present in the W direct data are shown by means of the wavelet analysis. As for long-period oscillations (Т ~ 60–90 years), possible relations of such quasi-periodicity with the phases of the North Atlantic Oscillation index characterizing the atmospheric circulation features are investigated. Calculated according to the MERRA array reanalysis, the mean anomalies of January – February average W series separately for groups of years with the values of the NAO index > +1 and ←1 demonstrated in their dynamics the values of different signs for the same Black Sea areas. It is revealed that during the periods when the index positive phase is mainly predominant, the W positive anomaly is formed over the south-western, south-eastern and eastern parts of the sea adjacent to the coast at a distance 20–100 km from it, and the W negative anomaly – over the rest of the sea. During the years when the index phase is mainly negative, the signs of the W anomalies over almost the same regions change to the opposite ones