Coastal erosion in 45 sandy beaches covering nearly 2000 km along the tectonically active Chilean coast is assessed during the last four decades. The historical analysis is based on the assessment of decadal changes of the shoreline position extracted from topographic surveys, aerial photographs, satellite images and survey maps using the DSAS software. Results show that 80% of the sites presented erosion rates (>−0.2 m/y), 7% beaches accreted (>0.2 m/y) while 13% remained stable. Eroded beaches include headland bay beaches, embayed and pocket beaches. A discussion on the possible causes explaining these results is conducted. While changes in offshore wave climate are spatially smooth within the region, relative mean sea level changes are highly variable and modulated by tectonic activity; the reduction of the sediment supply explains erosion rates in few cases.

Economic costs associated to coastal erosion are projected in 45 sandy beaches in Chilean coasts. We compare mid-century (2026–2045) and end-of-century projections (2081–2100) of wave climate and sea-level rise (SLR) with a historical period (1985–2004) using several General Circulation Models for the RCP 8.5 scenario. Offshore wave data are then downscaled to each site, where shoreline retreat is assessed with Bruun rule for various berm heights and sediment diameters. Results indicate that mid-century retreat would be moderate (>13 m) while larger end-of-century projections (>53 m) are explained by SLR (0.58 ± 0.25 m). A small counterclockwise rotation of long beaches is also expected. To assess the costs of shoreline retreat, we use the benefit transfer methodology by using adjusted values from a previous study to the sites of interest. Results show that, by mid-century, beach width reduction would be between 2.0% and 68.2%, implying a total annual loss of USD 5.6 [5.1–6.1] million. For end-the-century projections, beach width reduction is more significant (8.4–100%), involving a total annual loss of USD 10.5 [8.1–11.8] million. Additionally, by the end-of-century, 13–25 beaches could disappear. These costs should be reduced with coastal management practices which are nevertheless inexistent in the country.