O aporte sedimentar às praias da Cigana e do Cardoso, Cabo de Santa Marta, Santa Catarina, Brasil

Abstract

Santa Marta Cape (Laguna/SC) marks an abrupt change in the coastline orientation in southern Brazilian littoral. Prevailing NE winds blow seaward in the south sector of the cape where the aeolian transport represents a sediment supply to the beaches as well as longshore transport and continental drainage inputs. This study focuses on an integrated analysis of the coastal dynamics considering subaerial and subaqueous parts of Cigana and Cardoso beaches. The analysis was carried out through; (i) characterization of regional wind regime and sand drift potentials, (ii) analysis of historical changes in the dune field and coastline, and (iii) evaluation of the wave regime and sediment transport by longshore drift. The results show a significant decrease in the mobile dunes area between 1938 and 2012 due to growth of vegetation, deflation plains and urban settlements. During the same period, the coastline presented a retrogradation trend of about 0.5 m/yr which was intensified after 1978. The stabilization process of the dunefield probably contributed to aeolian sediment input decrease into the beach system in the last decades. This process could have changed the sediment balance of Cigana and Cardoso beaches, making the only significant sediment source represented by longshore drift. The model proposed for the longshore transport showed a divergence limit between two littoral cells in this sector, which does not provide the sediment input to the studied beaches. Thus, the divergent currents scenario limited the sediment supply by longshore drift to the study area as well as the presence of the cape trapping sediment transport from northern littoral cells.