A satellite view of riverine turbidity plumes on the NE-E Brazilian coastal zone

Abstract

Turbidity plumes of São Francisco, Caravelas, Doce, and Paraiba do Sul river systems, located along the NE/E Brazilian coast, are analyzed for their dispersal patterns of Total Suspended Solids (TSS) concentration using Landsat images and a logarithmic algorithm proposed by Tassan (1987) to convert satellite reflectance values to TSS. The TSS results obtained were compared to in situ collected TSS data. The analysis of the satellite image data set revealed that each river system exhibits a distinct turbidity plume dispersal pattern. The behavior, dimension and degree of turbidity of the São Francisco River plume have been greatly altered by the construction of a cascade of hydroelectric dam reservoirs in its hydrological basin. The plume has lost its typical unimodal seasonal pattern of material dispersion and its turbidity has decreased due to the regulation of river flow by the dams and TSS retainance by the reservoirs. In contrast, the Doce and Paraíba do Sul river plumes are still subject to seasonal pulsations and show more turbid conditions than the SF plume, as dams are less numerous, set in the middle river sections and the natural river flow has been maintained. The Caravelas Coastal System river plume is restricted to near shore shallow waters dominated by resuspension processes. During austral spring and summer when NE-E winds prevail, all plumes generally disperse southward. Short-term northward reversals may occur in winter with the passage of atmospheric cold fronts. The São Francisco and Doce river plumes tend to disperse obliquely to the coast and transport materials further offshore, while the Caravelas and Paraíba do Sul plumes tend to disperse mainly parallel to the coast, enhancing TSS retention nearshore.<br>O presente estudo analisa as plumas de turbidez dos sistemas dos rios São Francisco, Caravelas, Doce, e Paraiba do Sul localizados na costa NE/E do Brasil utilizando imagens Landsat e o algoritmo logarítmico para Total de Sólidos em Suspensão (TSS) proposto por Tassan (1987). Os resultados obtidos foram comparados com Total de Sólidos em Suspensão medidos in situ. A pluma de turbidez de cada sistema mostra padrões de dispersão distintos. O comportamento, a dimensão e o grau de turbidez da pluma do Rio São Francisco têm sido drasticamente alterados devido à cascata de barragens e seus reservatórios presentes em sua bacia de drenagem. Já as plumas dos rios Doce e Paraíba do Sul apresentam pulsações sazonais e maior turbidez, uma vez que as barragens nesses rios localizam-se no setor médio e mantiveram a pulsação sazonal da vazão. A pluma do sistema costeiro de caravelas permanece restrita às águas rasas dominadas por processos de ressuspensão. Durante a primavera e verão, quando os ventos de NE-E prevalecem, as plumas dos quatro sistemas se dispersam na direção sul. Durante o inverno, inversões do padrão de dispersão podem ocorrer com a passagem de frentes frias. As plumas dos sistemas São Francisco e Doce tendem a se dispersar obliquamente à costa, favorecendo o transporte de material para...

Fundamentals of Estuarine Physical Oceanography

“…continental shelf, after the river plume formation, extending its influence up to almost 10 km off shore of the estuary mouth. Turbidity plumes of the main estuaries located along the NE/E Brazilian coast were analyzed for their dispersal patterns of Total Suspended Solids (TSS) concentration, using Landsat satellite imagery to map the concentrations of suspended solid particles and its seasonal movements by Oliveira et al (2012). In situ sampling data were obtained from various oceanographic campaigns, conducted at the mouth of the rivers between 1994 and 2002.…”

Particle Fluxes and Bulk Geochemical Characterization of the Cabo Frio Upwelling System in Southeastern Brazil: Sediment Trap Experiments between Spring 2010 and Summer 2012

“…However, the role of the mediumsized mesotrophic Paraiba do Sul River (PSR) and plumes originating in the Guanabara Bay as potential sources of dissolved and particulate PARTICLE FLUXES ON THE CABO FRIO CONTINENTAL SHELF matter to the Cabo Frio shelf has been debated in the literature (Valentin et al 1978, Kahler and Voss 1996, Knoppers et al 1996, Oliveira et al 2012, and it is still poorly understood. The aim of the present study is to provide insight into the variability of the total and organic particulate matter fluxes and sources on the edge of the Cabo Frio continental shelf Upwelling System and to investigate the mechanisms underlying the sources and transport of particles on the shelf.…”

Pseudostomella dolichopoda Todaro, 2012 and P. cataphracta Ruppert, 1970 (Gastrotricha: Thaumastodermatidae): new records from Brazil and USA and an updated key to the genus

“…The Doce river has an annual average freshwater discharge of 900 m 3 ·s -1 (Oliveira et al 2012) and a sediment discharge 11.22 × 10 6 tons year -1 (Lima et al 2005), which is likely to disturb the benthic fauna. Until present, P. dolichopoda is only found south of the river outflow and P. squamalongispinosa only to the north.…”