Geohazard assessment of the coastal zone : the case of the southern Baltic Sea

Research by the Polish Geological Survey has been carried out along the southern Baltic coastal zone over a distance of 38 km. The Baltic Sea is classified as non-tidal, and its southern coasts are built entirely of weakly lithified sedimentary rocks. These deposits form three main types of coast, namely cliffs, barriers and alluvial coasts (wetlands), with the research focusing on the first two. Methods including remote sensing, mapping (geological, hydrogeological), offshore survey (bathymetric and geophysical measurements), laboratory analyses and modelling revealed a number of natural hazards. These are, respectively: (1) permanently occurring hazards, causing material damage such as: landslides, coastal erosion and seabed erosion; (2) incidental hazards such as dune breakage and storm surge overflow and (3) hypothetical threats that may occur in the future, such as hydrogeohazards defined here as flooding resulting from groundwater level rise or more rarely, earthquake threats.