Hydrological Threats to the Coasts of the Szczecin Lagoon in the Southern Baltic Sea

The Szczecin Lagoon’s shores and its water fluctuations were analyzed. The rates of shore retreat and other threats are presented for the period 2002–2026. This work aims to present shores prone to water and ice-shove erosion and flooding. The spatial distributions of different coasts and their morphologies and geology were examined. Data were obtained through field investigations following the strongest surges, and from secondary sources, including topographic information about the coasts. The hydrometeorological conditions in which erosion is likely to occur were investigated. Events associated with the highest water levels increase in the 21st century, and examples of their impacts on the shores are given. The relationship between sea-level changes and lagoon waters during the largest storm surges in the 21st century was analyzed. During storm surges, the water level (WL) in the lagoon may be 1 m above the mean sea level (AMSL), but run-up in the lagoon may reach up to 2 m AMSL. The length of the eroded coast has increased. An increasing number of small erosive coves are cut off in reed belts and shore sediments. Their annual retreat rate is 0.1–0.2 m. Large sections of the low-lying coast up to 2 m AMSL are prone to flooding during high water levels. The rate of retreat is 0.3–0.7 m/y on most eroded coasts prone to wind and surges. Due to the observed threats, several methods of coastal protection are used. These were analyzed and are presented in spatial terms.