Patterns of sediment dispersion coastwise the State of Bahia - Brazil

Abstract

Using the average directions of the main wave-fronts which approach the coast of Bahia State -coinciding with that of the main wind occurring in the area -and of their periods, we define a wave climate model based on the construction of refraction diagrams. The resulting model of sediment transport was able to reproduce, in a general way, the sediment dispersion patterns furnished by geomorphic indicators of the littoral drift. These dispersion patterns control the generation of different types of sediment accumulations and of coastal stretches under erosion. We demonstrate that the presence of the Abrolhos and Corumbaú Point coral reefs is an important factor controlling the sediment dispersion patterns, since them act as a large protection against the waves action. key words: Littoral drift, wave refraction, numerical modelling, State of Bahia, Brazil.

Deficit of sand in a sediment transport model favors coral reef development in Brazil

“…This divergence in the direction of sediment transport could have impeded the development of the Corumbau tombolo, and instead favored the establishment of the reefs. If so, the formation of the Corumbau Point should have initiated after the reefs reached sea level, a situation similar to the formation of the cuspate shape of the Caravelas Quaternary coastal plain in relation to the reefs of Abrolhos and Paredes (Bittencourt et al 2000). Regarding the region between Mutá Point and Salvador, it is significant that it is a coastal section with impeded littoral drift due to the existence of the islands and tidal inlets.…”

“…Drift cells converge also to between Salvador and Mutá Point, resulting in the accumulation of sediments in this coastal section. It should be emphasized that in relation to the Corumbau Point, that has a shape of a tombolo, its formation likely originated after the development of the reefs existing in front of it (Bittencourt et al 2000). In fact, in the region between Guaiú and Caravelas ( Fig.…”

A note on the occurrence of the encrusting foraminifera Homotrema rubrum in reef sediments from two distinctive hydrodynamic settings

“…The purpose of this work is to compare the Homotrema specimens collected from two different reef sites which are dominated by distinctive hydrodynamic settings: the Sioba and Rio do Fogo reefs, in northeast Brazil, which are in a broad shallow shelf, dominated by strong currents (Testa 1996), and the Praia do Forte coastal reefs, which are located in a narrow part of the eastern coast of Brazil, under the influence of wind-induced waves (Dominguez et al 1992, Bittencourt et al 2000.…”

Modelagem numérica da dinâmica do sistema estuarino Caravelas - Peruíbe, BA

“…Essa zona pode ser encontrada em estuários de variados tamanhos, formas e submetidos a distintas alturas de marés. Na ZTM, um grande volume de sedimentos em suspensão pode ficar retido dentro do corpo estuarino e passar por várias etapas antes da deposição final (Burchard & Baumert, 1998 (Dyer,1988 (Bittencourt et al, 2000), e recentemente modeladas (Andrade et al, 2003). Existem duas sequencias de ondas na área, as quais coincidem com o regime dos ventos.…”

“…Na região as frentes de onda de NE e E começam a interferir com o fundo marinho a uma profundidade aproximada de 20 m, enquanto as de SE e SSE começam a partir dos 35 m (Bittencourt et al, 2000). Em uma escala de 1:300000, Bittencourt et al (2000) mostram que a região de estudo é normalmente caracterizada por baixos níveis de energia de onda, com regiões de sombra de onda e grandes trechos de divergência de raios de onda, que são locais de enorme dispersão de sedimento.…”