Coastal Erosion on the Cocoa Coast: Bimonthly Shoreline Monitoring in Uruçuca, Ilhéus, and Una (2018-2024)

Objective: This study investigates coastal erosion along the Cocoa Coast (Uruçuca, Ilhéus, and Una) by performing bimonthly monitoring of the shoreline (SL) between 2018 and 2024 to identify the most vulnerable beach sectors. Theoretical Framework: Coastal erosion is recognized as a natural disaster under the Brazilian Classification and Codification of Disasters (Cobrade 1.1.4.1.0). The influence of anthropogenic structures, particularly the Port of Ilhéus, on sediment dynamics is highlighted as a factor that intensifies shoreline retreat. Method: Shoreline monitoring was conducted using the Digital Shoreline Analysis System (DSAS 6.0.170). Monthly PlanetScope satellite imagery (Dove and SuperDove), with spatial resolution of 3 m, was visually interpreted to vectorize the mean high tide line at 1:5000 scale. Shoreline displacement was quantified using the Net Shoreline Movement (NSM) statistic. Results and Discussion: The analysis revealed a general erosive trend, with peak retreat occurring during periods of high hydrodynamic energy (autumn and winter). The most intense events were recorded in July–August 2020 (–14.18 m) and May-June 2020 (–9.80 m). Research Implications: The results may guide coastal management and territorial planning by supporting the reorganization of coastal land use and promoting nature-based solutions (e.g., dune restoration) rather than rigid engineering structures that tend to transfer erosion downstream. Originality/Value: This research provides the first high-frequency (bimonthly) shoreline monitoring dataset (2018–2024) for one of the most erosion-prone regions of the Cocoa Coast, based on high-resolution PlanetScope imagery. It identifies seasonal patterns and critical erosion hotspots, offering significant value for coastal risk assessment.