Sediment Budget Correlation With the Southern Oscillation Index of a Foredune Westward of Cabo Frio (Rio de Janeiro)

Massambaba beach is located about 140 km eastward from Rio de Janeiro near cape Frio. The beach is exposed to a high energy environment, with storm surges from the South mainly in the autumn and winter. Winds blowing during all the year in the opposite direction (Northeast), remove sediments from the dunes to the beach and to the upper and middle shoreface, while the input of sediments to the dune system occurs during cold-front penetrations from the south trough wave overwash and aeolian transport. El Niño phenomenon lead to important changes in wind patterns in South America, due to the blocking of the polar frontal system in the western South Atlantic around the coast of the state of Paraná, in Brazil. This causes a decrease in the number of storm events in the Rio de Janeiro coast. Between April, 1996 and February, 2003 monthly topographic surveys were made in the area with the purpose to calculated the volumetric changes of the foredune segment. The results showed an erosive trend increased during the El Niño events with a volume reduction of 27% between the first and last survey. Besides this general trend of erosion, monthly variation in sediment volume indicated a relation with the Southern Oscillation Index.