Multi-temporal UAV analysis of beach–dune morphodynamics in Mrzeżyno on the southern Baltic coast (Poland)

This article presents a two-year multi-temporal unmanned aerial vehicle (UAV) survey of beach–dune morpho-dynamics near the mouth of the Rega River in Mrzeżyno (Poland) on the southern Baltic Sea coast. Between September 2020 and November 2022, ten UAV campaigns with RGB (Red, Green, Blue) and LiDAR (light detection and ranging) sensors were used to generate high-resolution digital terrain models of a 1-km-long beach–dune section and to quantify changes in shoreline position, beach and dune width and elevation, as well as their area and volume. The monitoring captured repeated dune scarping, beach erosion, and partial post-storm recovery driven by energetic storm events and storm clusters. During the study period, the dune toe was locally lowered by up to 2.8 m, dune volume decreased by approximately 14,300 m³, and dune area shrank by about 3,600 m², while the beach area increased by roughly 6,000 m². Coupling these morphometric indicators with hydrological and meteorological records from a nearby tide gauge shows that storms with wave heights above 3 m, water levels up to 1.2 m above mean sea level, and durations exceeding 66 h exerted the strongest control on dune erosion in the study area. The study highlights the importance and usefulness of RTK-equipped UAV systems, particularly UAV-LiDAR, for coastal geomorphological surveys, as they provide accurate, repeatable, and high-resolution terrain data for continuous monitoring of storm-driven changes along vegetated dune coasts.