Coastal erosion in central Chile: A new hazard?

The coasts of central Chile are increasingly affected by human activity. To date, there are no clear symptoms of shoreline change in the area; however, the incidence of recent extreme storms, in conjunction with an increase in urban area, may have created a new coastal hazard in addition to earthquakes and tsunamis. In this context, coastal erosion on four urban beaches on Valparaíso Bay was analyzed on a decadal scale. Satellite images and topographic surveys were used in order to determine spatio-temporal changes in the shoreline. These changes were linked to the long-term behavior of oceanographic variables such as wave climate and mean sea level. The analysis shows that Reñaca Beach experienced an accretion of 12.6 m between 1964 and 2006, while Los Marineros and Las Salinas proved to be in stable conditions in the same period. Caleta Portales, in contrast, was significantly affected by a shoreline retreat of 12.6 m between 2004 and 2016. In all cases, erosion rates increased due to i) the sea level rise of up to 30 cm observed during ENSO warm phases and ii) an increase in the frequency of extreme storms, which shifted from nearly 5 events per year in the 1960s to more than 20 in recent years. The erosive trend found in the last decade suggests that this coast could deteriorate if such factors are maintained or intensified. A set of preliminary engineering measures, in conjunction with sediment managing schemes, are proposed for the sustainable development of the coastal zone.