Changes on coasts of western Estonia and Russian Gulf of Finland, caused by extreme storm Berit in November 2011

The study is analyzing the meteorological parameters, hydrodynamic conditions and coastal changes caused by extreme storm known as Berit, which travelled across the Baltic Sea from 27th to 29th of November in 2011. Wind speed on West Estonian islands reached to 19,7 m/s (gusts 29 m/s), 20,4 m/s on the northern coast (gusts 27 m/s) and 15 m/s (gusts 20 m/s) on the Russian Gulf of Finland coast. Sea level at Pärnu reached to 110 cm, 142 cm at Narva-Jõesuu and +190 cm near St Petersburg (outside from the Flood Protection Facility). Shorelines, scarp positions and beach profiles were measured at the end of summer in several sites along Estonian coast and Russian Gulf of Finland coast. Two researchers spent the whole duration of the storm in Harilaid Peninsula and recorded changes in shoreline, scarp positions and beach profiles. Wave run-up and sea-levels were also recorded. All the measurements were carried out using DGPS with the accuracy of 1 cm in vertical and horizontal scale. Russian study site was measured a few days after the storm. In order to assess variations in forcing conditions during the storm a wave hindcast was performed using a SMB-type wave model. Calibrated against the field measurements, the model is forced by wind data, and it calculates significant wave parameters for a chosen location. Significant wave height 1.5 km off the Kelba study site was 2.8 m and maximum waves reached to 4.4 m. The first results indicate that 1.5 m high sandy scarp in Cape Kiipsaare receded up to 4 m. The loss of sand was ca 6 m³ per 1 m of shoreline. The speed of recession was around 0.6 m/h during the peak of the storm. The length of gravel-pebble spit at Kelba increased and new gravel ridges in the proximal part reached to 2.8 m. In the Russian part of the eastern Gulf of Finland as a result of storm and flood the scarp up to 2 m high was formed along 15 km of dunes of the northern coast (Komarovo, Repino). It was the first strong erosion - vent observed after extreme dune´s damage during autumn 2006-winter 2007.