Beaches in the state of Bahia: The importance of geologic setting

Abstract

The state of Bahia with approximately 1000 km of shoreline, a great heterogeneity of exposed rock types and subjected to varying degrees of sediment supply allowed us to investigate the controls exerted by these factors in determining the beach types. The modal morphodynamic states of the beaches of Bahia is dominantly controlled by sediment grain size, which in its turn results from the long term history of the coastal zone. Locally sourced sediments, eroded from the coastal tablelands (Barreiras Formation), are predominantly coarse grained favoring reflective beaches (Sediment Starved Southern Coast). Distally sourced sediments, as in the case of large rivers are predominantly fine to very fine sands, resulting in a dominance of dissipative and high-energy intermediate beaches (Deltaic Coast of the Jequitinhonha River). Shoreline stretches nourished by small rivers are characterized by medium size sands and a dominance of intermediate high energy beaches (Northern Littoral Coast Compartment). Finally, the stretch of the coast fronted by Mesozoic Rifts, characterized by a great heterogeneity of sedimentary rock types and small sediment supply, have a very irregular shoreline, bordered by fringing reefs. In this section low energy sheltered beaches dominate.