A significant longshore transport divergence zone at the Northeastern Brazilian coast: implications on coastal Quaternary evolution

Abstract

By using the mean directions of the wave-fronts approaching the Brazilian northeastern coastal stretch comprised between the localities of Real river (Sergipe State) and Galinhos (Rio Grande do Norte State) - coincident with those of the main winds occurring in the area - and their periods, we have defined a wave climate model based on the construction of refraction diagrams. The resulting model of sediment transport, as obtained by numerical modelling from the refraction diagrams, taking into consideration the angle of approach and waves heights along the 10-m isobath, was capable of reproducing the patterns of sediment dispersion provided by geomorphic indicators of the longshore drift. All this coastal region, approximately 900 km in length, is characterized by a significant divergence zone in the direction of net longshore drift of sediments, the potential intensity of which increases considerably in value, in almost its entire length, continuously toward downdrift, which might explain the greater or lesser long term susceptibility to erosion, during the Quaternary, along the coastal stretch studied.