Quantification of coastal erosion rates using Landsat 5, 7 and 8 and Sentinel-2 satellite images between 1986-2022. Case study: Cartagena Bay. Valparaíso, Chile.

In recent years, coastal erosion has become one of the many natural hazards affecting Chile's sandy coastlines. Currently, more than 90% of the sandy coasts of Valparaíso drop off from coastal erosion. Cartagena Bay, located in the municipality of San Antonio, is one of the coastal areas with the greatest transformations caused by extreme events and anthropogenic activities. These transformations require continuous monitoring, and medium-resolution optical satellite imagery is seen as an invaluable resource for tracking these coastal changes. In this study, a littoral analysis is presented that combines optical satellite imagery, simulation-derived wave climate, in situ data, the SHOREX system developed in Python, and GIS-based tools such as DSAS to quantify rates of change in the Bay over the period 1986-2022. Satellite-derived shorelines were used to identify erosion hotspot areas in the Bay, differentiating the impact of erosive processes associated with ENSO hydrometeorological phenomena, the 27-F 2010 earthquake and tidal waves from 2015-2022, which lead to major transformations in the morphodynamics of the beach. The results show that the Bay is currently undergoing high erosional processes in 20% of the coastline with values < -1.5 m/year and 50% with erosion rates ranging from [-0.2 to -1.5 m/year]. Since 2015, these processes have been accentuated, due to increased swells throughout the year. The results were validated with data taken in the field during the satellite revisit days and a pressure of 4.52 m was obtained, guaranteeing sub-pixel precision.