Symulacja i predykcja erozji wybrzeża wybranych odcinków Zatoki Gdańskiej w modelu SWAN

The increasing climatic changes and their possible negative impact on the marine and coastal environment prompt the search for alternative estimating and predicting dangerous phenomena. Hydrodynamic modeling is an underappreciated model which enables forecasting waves and their effects. In the presented work, the author assessed the influence of the dynamics of undulations on the morphological changes of the Gulf of Gdańsk coast in three transects representing different geomorphological zones of the shore. Using the SWAN wave model, simulations were carried out reflecting the hydrodynamic conditions of the most giant storms in 2015-2020, calculating the amount of eroded sediment material in bottom and suspension transport. In addition, based on the significant wave height data from ERA5-ECMWFfrom 1981-2020 and the assumed scenarios, a prediction was made of a potential increase in coastal erosion caused by the rise in the mean value of the significant wave height. Taking into account the implemented and set atmospheric, hydrodynamic, and sedimentological conditions, it has been estimated that the highest erosion characterizes the cliff area in Gdynia-Orłowo (transect B), where the average amount of erosion of the bottom sediment is 0.5 kg/m/s, of the sediment in suspension - 20 kg/m/s, and the average speed of the transported sediment exceeds 2 m s-1. The lowest dynamics of changes is characteristic for the western part of the Vistula Spit (transect C), where the average velocity of the transported sediment is 0.28 m s-1, and the average size of the eroded bottom sediment is 0.014kg/m/sand 0.15kg in suspension/m/s. In the analyzed storm events, at all locations, the greatest erosion was generated by the wave conditions from January 2019. The maximum wave height in the open sea was record-breaking, over 13 meters. Depending on the analyzed area and its geomorphology and exposure to storm waves, the predicted amount of erosion varied significantly. For Scenario A, assuming a 15% increase in the average frequency and height of the significant wave, the forecast of coastal transport is 138-161 thousand m3/year, for Scenario B (30%) 150-175.5 thousand m3/year, and for Scenario C (50%) 180-210 thousand m3/year. In addition, the aim of the work is a cause-and-effect analysis of wave activity on the coast of the Gulf of Gdańsk and the assessment of its impact on quantitative changes in the sediment transport balance.