Beyond the 2023 Surge: Quantifying Shoreline Dynamics in the German Baltic Sea with Sentinel-2

Monitoring coastal zones is essential for evidence-based coastal management. Commonly applied methods and technologies like beach surveys, aerial imagery, and Light Detection and Ranging (LiDAR) provide highly accurate data but are often limited in spatial coverage or monitoring frequency due to high costs. Satellite remote sensing has emerged as a promising and cost-effective alternative, offering frequent, large-scale shoreline observations. To facilitate rapid and precise satellite-based shoreline change analysis across large regions, we developed the Shoreline Extraction and Change Analysis Tool (SEaCAT). This Python-based toolkit leverages cloud technology to semi-automate key stages of data processing, including scene selection, shoreline extraction, and change analysis. We employ SEaCAT to assess the impact of the October 2023 storm surge on coastal morphology in two regions along the German Baltic Sea coast. By analysing the entire Sentinel-2 archive (July 2015 – June 2024), we contextualize the event within broader morphodynamic trends and observe post-storm recovery. Our findings reveal that due to differences in the surges’ duration and intensity, it had a significantly higher morphodynamic impact in Angeln, Schleswig-Holstein, compared to Mönchgut, Mecklenburg-Vorpommern. Despite this, recovery processes in the months after the surge mitigated the surge's effects along most coastal sections. However, the Schleimünde sand spit emerges as an erosion hotspot, experiencing continued coastal recession for approximately six months post-surge due to a dramatically altered spit profile. Our study demonstrates that, although satellite-based shoreline monitoring may not achieve the accuracy of commonly employed methods, its frequent observations and low costs make it a valuable complement to existing monitoring strategies.