Meteorological tides and episodes of severe coastal erosion on the coast of Salvador, Bahia State, Brazil

Abstract

The coastline of Bahia State, Brazil, in the eastern sector of the northeastern region of Brazil, has a total of 20 beaches, 14 of which are located on the open sea (Atlantic Ocean), while the others are sheltered in the Todos os Santos Bay. Many of these beaches have been or are currently being affected by episodes of severe coastal erosion which are intrinsically related to both anthropogenic and natural processes. This study aimed to use statistical analyses of information and data, such as photos, texts from local newspapers, synoptic maps and reanalysis data from the National Centers for Environmental Prediction to identify severe erosion events related to meteorological tides on the Salvador coastline during the period from 1965 to 2006. The results show that most erosion events appear to be associated with the occurrence of meteorological tides and have great destructive potential. We found that the combination of i) the occurrence of spring tides with ii) the arrival of cold fronts and/or coupling of a high pressure system with a trough in the lower levels of the atmosphere and iii) winds predominately from S and SE, that through Ekman transport, promotes pilling up of water against the coast, favours the increase of the water level and wave height and range along the coast.