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176D. MUEHEFigure 5. Highly developed double coastal barriers andenclosed lagoons in Barra da Tijuca, Rio de Janeiro.Photo D. Muehe.changes in the wave incidence in response to climatechanges, and those changes are reflected inadjustments of the shoreline through the process ofbeach rotation.In areas of high relief, as represented by thesedimentary deposits of the Barreiras Group andother morphologically similar areas which occurdiscontinuously from the coast of Amapá up to Riode Janeiro, the result of transgressions were theformation of coastal cliffs, in some places stillactive, preceded by narrow beaches and a nearshoreand inner shelf of low gradient (Fig. 7). A risingsea level will increase the erosion of the cliffs, aslow process whose speed depends on the cohesionof the material and the amount of sedimentreleased and maintained in the profile. Many of thecliffs that are still active probably represent anincomplete adjustment related to the post-glacialtransgression rather than the result of a recent rise insea level.The erosion of sedimentary cliffs leftvestiges of their past position in the form of lateriticconcretions deposited on the continental shelf, andthe released sediments represented an importantsource of sand for the formation of beaches, dunesand coastal terraces.Figure 7. Active cliffs in sedimentary deposits of theBarreiras Group. Buzios, Rio Grande do Norte. Photo D.Muehe.Figure 6. Beach ridges of the Doce River coastal plain.Image from Google Earth.Coastal Compartments and AssociatedVulnerabilitiesPhysiographic coastline classifications, forthe Brazilian coastline, have been proposed byseveral authors. The most largely known wasproposed by Silveira (1964) who consideredgeological, geomorphological, climatic and oceanographicaspects. More recent studies (Muehe 1998,2005, 2006, Muehe & Neves 1995, Dominguez2004, 2007) are in many aspects coincident with thePan-American Journal of Aquatic Sciences (2010) 5(2): 173-183