Satellite-Based Assessment of Coastal Morphology Changes in Pichilemu Bay, Chile

Coastal erosion is a global issue exacerbated by extreme events, ENSO variability, storms, and anthropogenic pressures. In Chile, over 80% of beaches are affected by erosion, impacting more than one million people. This study analyzes the evolution of Pichilemu Bay between 1985 and 2024 using satellite imagery, spatio-temporal models, and drone-based surveys. A total of 554 shorelines were extracted, revealing and average shoreline retreat of −1.17 m/year, with maximum erosion of −1.76 m/year and maximum accretion of +0.9 m/year. Wave climate analysis (mean Hs 2.5 m, mean Tp 12.5 s) identified 10 major storm events exceeding 3 m, while sediment sampling showed significant negative correlations between grain size and erosion rates (r = −0.64, p < 0.05). The morphology before and after the 2010 earth-quake was assessed, evidencing up to 100 m of shoreline retreat in affected sectors. Remote sensing techniques proved highly effective for monitoring coastal dynamics, providing high-resolution insights that inform spatial planning, enhance regional erosion monitoring programs, and support adaptive management strategies in the face of climatic and tectonic challenges.