The article presents results of studies on the rate of erosion of the Wolin Island cliff-coast (NW Poland) during the last three decades. Trends of geomorphological changes were defined based on multiannual observations . Changes were controlled by secular and extreme processes. Research has shown that the intensity of the processes shaping the Wolin Island cliff-coast were characterized by a clear seasonal variability. Analysis of hydro-meteorological conditions allowed the authors to derive the threshold values of the most important factors initiating cliffs hazard. The destruction of the cliff, differing in range, occurs in the above-threshold conditions. Multiannual research and direct observations of the functioning of the cliff-coast conducted herein provided the basis for proposing the safety shield and information system about the cliff hazard.

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The aim of the article is to present the temporal and spatial variability of the cliff coast erosion of the Wolin Island in 2012–2020 in three time periods (2012–2015, 2015–2018, 2018–2020). The research used data from airborne laser scanning (ALS), based on which DEM models were made. Based on the differences between the models, the amount of sediment that was eroded by the sea waves was determined. The conducted research showed that, in the analyzed period, the dynamics of the Wolin cliffs were characterized by high variability. The greatest erosion was observed on sandy cliffs, and the smallest on clay cliffs and on cliffs that are densely covered with vegetation. In the sediment budget studies, two seashore erosivity indicators were proposed: length-normalized sediment budget (LB) (m3/m) and area-normalized sediment budget (AB) (m3/m2). The average annual dynamics of the cliff edge erosion on the Wolin Island was found to be LB = 6.6 ± 0.3 m3/m/a, AB = 0.17 ± 0.01 m3/m2/a. The results obtained are comparable with other postglacial cliffs. The use of the differential analysis of DEM models allows for the determination of the dynamics of the cliff coast and may be used in spatial development and planning of seashore protection zones.

Zarys treści: Artykuł prezentuje wyniki badań nad aktywnością procesów osuwiskowych na wybrzeżu klifowym wyspy Wolin wywołanych silnymi wezbraniami sztormowymi oraz intensywnymi opadami atmosferycznymi. Badania opierały się na studium pięciu przypadków dotyczących wykształcenia lub przeobrażenia osuwisk klifowych. W wyniku przeprowadzonej analizy zaproponowane zostały wartości progowe odporności systemu stokowego na oddziaływanie takich czynników morfogenetycznych jak wezbrania sztormowe i opady atmosferyczne. W przypadku przekroczenia wymienionego czynnika wartości progowej w obrębie klifu dochodzi do wykształcenia osuwiska. Należy nadmienić, iż inicjacja procesu osuwiskowego warunkowana jest także wieloma innymi czynnikami, które najczęściej mają charakter wybitnie lokalny (morfologia, litologia, hydrogeologia, itd.). Wobec powyższego należy stwierdzić, iż przedstawione wartości progowe są wartościami koniecznymi do wystąpienia procesów osuwiskowych, jednak z uwagi na złożoność tych procesów, w niektórych przypadkach mogą one nie stanowić wartości wystarczających.

Abstract. Climate changes, sea transgression and sea coast erosion observed today cause dynamic changes in coastal ecosystems. In the elaboration, cause and effect interrelations between abiotic hazards (hydrometeorological conditions and sea coast morphodynamics) and biotic (Cephalanthero rubrae-Fagetum phytocoenosis) components of natural environment have been defined. An up-to-date phytosociological analysis of a very valuable Cephalanthero rubrae-Fagetum site on cliff tableland was conducted in the context of hitherto temporal variability of climatic conditions and the rate of cliff coast recession. Also, the development prognosis of the researched site in the 21st century is provided, with respect to the expected climate changes and cliff's morphodynamics. The conducted research actions revealed the influence of global hazards (e.g. climate changes, sea transgression and sea coast erosion) on changes in the natural environment on regional scale (with the example of the site of Cephalanthero rubrae-Fagetum on a cliff coast of Wolin island in Poland). It has been established that in the 21st century, a relatively larger hazard to the functioning of the researched site is climate changes (i.e. mostly changes in thermal and precipitation conditions) not the sea coast erosion.