Los efectos del fenómeno El Niño en la ocurrencia de una alta tasa de erosión costera en el sector de Punta Gorda, Esmeraldas

Abstract

Los objetivos de este estudio fueron: - Cuantificar el retroceso de la línea de costa en un período de 30 años en el área de Punta Gorda. - Estudiar la formación de la plataforma de abrasión relacionada con este retroceso. - Estudiar el proceso de erosión para establecer su continuidad y características.

We made a quantitative study of coastal erosion in the area of Punta Gorda (Esmeraldas), which is related to the formation of a wave cut platform, a process similar to the formation of Quaternary marine terraces during the former interglacial periods. This study was made using multitemporal data from aerial photos of 1971 and 1983, which have been compared with the position of the coast line in 2001, established by a new topographic levelling. We observed a mean rate of 1.5 to 2.3 m/y according to the position of the coast segment. The retreat is discontinuous, low or even negative when important landslides occurred as it appears during El Niño periods. For example the 198271983 El Niño event produced a temporary seaward displacement of the coast line until the marine erosion re-establish the morphology. However the resulting effect of El Niño periods is to break the structure and stability of the coastal cliff, favoring an easier and faster cleaning of the sliding material. Regarding the extension of known wave cut platforms the observed rate retreat seems very high. This is interpreted as an increasing effect of the El Niño periods during the last decades.