Gravel-pebble Shores on Saaremaa Island, Estonia, and the Relationship with Formation Conditions

The Estonian seacoasts in general can be characterized by their embayed nature with a variety of shore types experiencing tectonic and isostatic uplift ranging from 0.5 to 2.8 mm/year. Accumulative coastal landforms develop in different ways at different locations. The greatest changes on gravel-pebble shores usually result from extremely strong storms in high sea level conditions. This article examines three study sites. They are all located in northwest Saaremaa Island and are all composed of gravel-pebble shores, but each has a different exposure to the open sea. The achieved results are based on the cartographic analysis and the fieldwork data. A clear increasing trend of storminess can be observed during the second half of the 20th century in Estonia and the whole Baltic Sea region. The maximum was recorded in the 1980s when there were 27 stormy days per year on average. The frequency of storms has been more or less stable during the last decade but the maximum sea levels during storm surges continue to increase. The average annual maximum sea levels during storm surges have steadily increased from 91-100 cm in the middle of the previous century to 122-138 cm at the beginning of the current century. An analysis of the storm characteristics and the morphometric parametres of the shore formations show that the greatest changes in the position, contour and size of such shore formations are considerably more dependent on the high sea level during a storm than on the frequency of storms.