Storm-Driven Coastal Erosion and Shoreline Dynamics along the Southern Baltic Sea Coast: A LiDAR and Wave Hindcast Study

Coastal erosion along the southern Baltic Sea was analysed using airborne LiDAR surveys from 2011, 2012 and 2022 combined with a 12-year wave hindcast based on SWAN/ECMWF reanalysis and data provided by the Finnish Meteorological Institute (FMI). A coastal strip approximately 200 km wide, including cliffs or dunes, beaches and the shallow nearshore zone, was investigated to quantify volumetric changes and their relationship to storm-wave conditions.

Storm events were identified using two thresholds: significant wave height Hs ≥ 2 m and Hs ≥ 4 m with a minimum duration of 12 hours. Three offshore points located along the Polish coast were analysed to assess spatial variability in storm frequency, wave height and wave direction. The results indicate strong contrasts in storm exposure, with the central–eastern sector being the most affected and the western sector strongly sheltered.

LiDAR-based differencing revealed a pronounced west–east erosion gradient. Cliffed sectors exhibit deep but spatially limited erosion (class 1, >10 m A.S.L.), whereas low-lying barrier and deltaic coasts are dominated by widespread abrasion in the 1-5 m A.S.L. The total abrasion volume between 2011 and 2022 reached  - 16.6 million m³.

To capture spatial variability, shoreline change rates were computed on a regular 1-km grid along the entire coastline, revealing alternating erosion and accumulation cells strongly controlled by coastal morphology and storm-wave exposure. In addition, erosion volumes were aggregated at the municipal level to estimate potential economic impacts related to the loss of land, tourist infrastructure, coastal protection assets and ecosystem services. The highest potential economic losses were identified in municipalities with cliffed coasts and densely developed tourist zones, whereas lower impacts characterize sparsely developed, low-lying barrier coasts.

The results demonstrate that storm-wave climate, coastal morphology and local socio-economic conditions jointly control the magnitude and spatial distribution of coastal erosion risk along the southern Baltic Sea.