Long-Lasting Baltic Storm Surge Highlights Coastal Vulnerability in 2009

This paper examines the hydrometeorological conditions and coastal impacts of the Wimar storm surge that affected the southern Baltic coast in October 2009. The study focuses on the relationship between sea level, significant wave height, wind speed, and the resulting erosion of the dune coast.Hydrometeorological data were analysed to characterise the development and duration of the storm surge, while morphological changes were assessed using field measurements conducted as cross-shore profiles before and after the event. The extent of dune retreat was calculated and related to sea level, beach elevation, and shore exposure.The Wimar storm was characterised by an unusually prolonged period of elevated water levels associated with winds from the NE sector. The resulting storm surge caused extensive coastal inundation, with water levels reaching up to 2.5 m above mean sea level (AMSL) in the affected areas. Mean dune retreat was 3.3 m, with a maximum retreat of 8 m. The magnitude of erosion varied spatially and was controlled by the duration and elevation of the storm surge, beach elevation and coastal exposure. Beaches with elevations lower than the storm-induced water run-up level provided insufficient protection against wave attack and caused the dune toe retreat. The prolonged high-water conditions resulted in extensive flooding of low-lying coastal areas, reaching elevations of approximately 3 m AMSL, and caused damage to numerous coastal protection structures, including artificially nourished beaches and dunes.