The main morphological difference between Cibratel and Itanhaém Suarão beaches is due to the presence of the Itanhaém river mouth in the second one. Eight monthly beach profiles were done during fourteen months. Simultaneously sediments were sampled in the shoreface and incident waves characteristics were visually estimated. Sediment sampling and bathymetry were done in the adjacent submerged area. The results show that, despite of the predominance of the action from the Tropical South Atlantic Anticyclone (TSAA) over the wave regime, the sedimentation process dynamics from the beaches was mainly controlled by the incidence of frontal systems, leading to a more effective northeastward longshore transporto Aerial photographs and beach sediment characteristics confirm such tendency. At Cibratel beach, the southwestward transport caused by TSAA was more evident than in Itanhaém - Suarão beach. Modifications in the beach dynamics, caused by the presence ofthe Itanhaém river mouth occurred only in restricted areas of its vicinities.
Beach morphodynamic; Frontal systems; Swell