Soft postglacial cliffs in Poland under climate change

Abstract

The paper presents the results of the simulations of soft cliff erosion in Poland under future sea level rise. Two locations were investigated: one situated on the Wolin island, and the second near the town of Ustka. The cliffs will be suffering enhanced erosion for a number of reasons. First, the adopted sea level rise of 0.7 m results in a direct attack on cliff foot, leading to enhanced erosion with rates being roughly twice as high as that occurring without the rise. A high rate of erosion can persist because the cliff cannot reconfigure itself by moving landward and will permanently remain exposed to wave attack even under milder regimes. Second, the wave climates in the Baltic Sea release most energy in close shoreline proximity. Third, longer storm event durations can lead to ‘erosion saturation’, but this result requires further investigations, which will include alongshore effects induced by local bathymetry and longshore currents, ignored in 1-D simulations. Finally, the granulometry was found less important; finer grains offer less resistance to depletion, leading to greater erosion. The results demonstrate the need for vast follow-up research: (1) detailed mapping of the bathymetry near cliffs in order to properly reproduce alongshore redistribution of sediment during storms and achieve better estimates of cliff erosion, (2) detailed mapping of cliff lithology in order to properly reproduce their sediment composition and thus achieve better estimates of built-in susceptibility to erosion, (3) preparation of 2-D modeling suites for improved assessment of the rates of erosion of cliffs subjected to sea level rise.