Playas críticas por erosión costera en el caribe sur de Costa Rica, durante el periodo 2005-2016Critical beaches due to coastal erosion in the Caribbean south of Costa Rica during the period ResumenDesde el 2010 en la prensa local se ha venido reportando un proceso acelerado de erosión en playas arenosas del litoral caribeño costarricense, que incluso ha sido documentado al interior de las áreas protegidas. Para cuantificar este proceso e identificar los puntos calientes por erosión costera en el Caribe Sur, se planteó una metodología que consiste en levantar la línea de costa a partir de fotografías áreas e imágenes satelitales de alta resolución espacial, con el fin de determinar la tasa de retroceso de la costa. Las fotos e imágenes utilizadas cubren un periodo entre 2005 y 2016. De esta forma fue posible identificar once puntos calientes de erosión, así como la estimación de sus tasas areales de retroceso para dos periodos (). En este sentido, las localidades que han experimentado la mayor erosión en sus playas arenosas son el Parque Nacional Cahuita, Westfalia y playa Bananito.Palabras clave: erosión costera, Caribe costarricense, dinámica costera, provincia de Limón, erosión de playas.

The great variety of climatic conditions, tidal ranges and wave regimes of South and Central America act on a complex geology and tectonic framework. Many of the rock and cliffed coasts of South America are strongly controlled by the occurrence of extensive Cenozoic and Pleistocene sediments that crop out at the coast. Geology and the different uplift rates are a major factor in the whole coastal geomorphology of South and Central America, and consequently are a very important control of the processes and landforms of rock coasts. This chapter covers several aspects of the rock coast of South and Central America, with special attention to the combination of tectonic movements and Quaternary Pleistocene-Holocene sea-level changes.

Costa Rica has been affected by several local and distant tsunamis in the past, but the historical information is scarce and incomplete. Its Pacific coast stretches for over a thousand kilometers, and tsunami hazard has never been evaluated for its full extent. Numerical modeling of tsunami propagation and inundation is a useful tool to assess tsunami hazard, particularly in cases with limited historical information available. Here, we perform a first estimation of tsunami hazard for the Pacific coast of Costa Rica from seismogenic sources, by numerical propagation of 57 local and distant tsunamis to a depth of 20 m. The results of our study identified tsunami sources that are particularly threatening for Costa Rica and determined locations with higher tsunami hazard. For the analysis, the Pacific coast of Costa Rica was divided into segments and subsegments based on differences in continental slope morphology. Subsegments with higher tsunami heights were Southwest Nicoya Peninsula and West Osa Peninsula, and in a lesser extent North Guanacaste, North Nicoya Peninsula, and Central Pacific. Regions with long and gentle slopes and narrow continental shelf were affected by higher tsunami waves, due to more efficient tsunami energy transmission to the shelf and reduced energy loss while traveling through a narrow shelf. On the opposite, steeper continental slopes reflected most of the tsunami energy, causing smaller tsunami heights nearshore, regardless of the shelf width. Nevertheless, other effects played a major role, like curved coastlines that focused tsunami energy, wave refraction, interference, and trapped edge waves. Distant tsunamis dominated the threat, with tsunamis coming from the Tonga-Kermadec and the Colombia-Ecuador Trenches causing the greatest heights due to directivity, and arrival times of about 15 h and 75 min, respectively. Local tsunamis had short arrival times but a localized impact, mainly at the shoreline in front of the generation region but were also affected by tsunami focusing, wave refraction, and edge waves. Outer rise and Osa sources caused the lowest impact within local sources. These results provide a guide for emergency planners to prioritize coastal locations and tsunami sources for tsunami preparedness actions and warning protocols.

Since 2010, the local press has been reporting an accelerated process of erosion on the sandy beaches of the Costa Rican Caribbean coast, it has even been documented within protected areas. To quantify this process and identify coastal erosion hotspots in the Caribbean south, a methodology was proposed for detecting and delineating the shoreline using aerial photographs and high-resolution satellite imagery to determine the rate of shoreline retreat, the employed photographs and images cover the period between 2005 and 2016. By such means it was possible to identify eleven erosion hotspots, as well as estimation of their retreat rates for the periods 2005-2010 and 2010-2016. The localities that have experienced the greatest erosion of their sandy beaches are Cahuita National Park, Westfalia and Bananito Beach.