Coastal morphodynamic and geomorphological compartments along the northeast littoral of Rio de Janeiro state, Brazil

The northern littoral of Rio de Janeiro state, extending from Cabiunas to Atafona (Paraiba do Sul River mouth), is a continuous wave-dominated sandy coastline, showing distinct geomorphological characteristics along the coastal plain and the adjoining continental shelf The region of Cape Sao Tome, associated with the Sao Tome submarine shoal, defines a change on the coastline trend direction, separating distinct geomorphological sectors. Northwards, the coastal plain is characterized by a progradational beach ridge plain associated with a low gradient inner continental shelf, whilst southwards the coast is featured by a transgressive sandy barrier associated with a high gradient inner shelf An integrated study of the coastal and continental shelf geomorphology together with the analysis of spatial and temporal variability of beach profiles were undertaken to investigate the relationship between the shoreline morphodynamics and the geomorphological compartments. Four cornpartments were recognized based upon beach morphology, shoreline mobility, coastal and shelf geomorphology, and influence of distinct wave climate. Prograding coasts associated with a low gradient inner shelf are related to low mobility shoreline and intermediate morphodynamic beach states, whilst the transgressive sandy coast, associated with high gradient inner shelf, correlates to the low mobility shoreline index and reflective morphodynamic beach state. High mobility shoreline indexes were observed associated with: (a) the Atafona compartment, which is defined by the Paraiba do Sul River mouth and an erosive beach profile; and (b) them Cape Sao Tome compartment, defined by a beach ridge plain formed by longshore convergent currents during marine transgression.