%0 Journal Article
%T Morphodynamics in the Confluence of large regulated Rivers: the case of Paran¨¢ and Paranapanema Rivers
%A Jos¨¦ C. Stevaux
%A Renato J. Paes
%A Andr¨¦ Amancio Franco
%A M¨¢rio L. de C. Etchebehere
%J Latin American Journal of Sedimentology and Basin Analysis
%D 2009
%I Asociaci¨®n Argentina de Sedimentolog¨ªa
%X The confluence of the Paran¨¢ and Paranapanema Rivers is studied according to morphology and dynamics. It is probably the only example of this type of fluvial environment involving a large, tropical and intensive regulated river. Confluence channels were monitored along a hydrological cycle (high-low water level) in terms of morphology, flow velocity, magnitude, structure, and bedload dynamics. In this case, hydrology is controlled by the flow of the tributary, which develops a continuous and well-defined thalweg since the collector channel (a secondary channel of the Paran¨¢ River) that presents relatively large bedforms that reduce stream power by increasing roughness. Although significant differences in channel morphology were not observed along the hydrological year, bed material texture indicates that the channel bottom is suffering a slight armoring process. This is probably the reason for the large asymmetry of channel confluence where the depth of the tributary channel is larger than that of the main collector channel (the Paran¨¢ left branch). The Rosana Dam, closed in 1987 and located 26 km upstream from the confluence, is the cause of the changes in sediment transport and the generation of the channel pavement. With the closing of the Porto Primavera Dam (2000) in the Paran¨¢ River (27 km upstream from the confluence) a new morphodynamics is foreseen for this environment, and this paper can be seen a relevant pioneer reference for environmental monitoring and management. A morfologia da conflu¨ºncia de rios intensamente regulados de grande porte ¨¦ estudada tendo como exemplo a conflu¨ºncia dos rios Paran¨¢ e Paranapanema. Para este trabalho foi realizado o levantamento batim¨¦trico de detalhe em dois per¨ªodos do ciclo hidrol¨®gico (cheia e vazante), a velocidade e estrutura da corrente e o tipo da carga de fundo. A hidrodinamica da conflu¨ºncia ¨¦ controlada pelo rio tribut¨¢rio, que desenvolve um talvegue bem definido e cont¨ªnuo. O canal coletor (canal secund¨¢rio do rio Paran¨¢), uma vez que possui grande carga de fundo constitu¨ªda de formas de leito de relativa express o topogr¨¢fica, tem sua pot¨ºncia de canal reduzida (aumento da rugosidade). Por outro lado a aus¨ºncia de carga do rio Paranapanema propicia a forma  o de um canal mais fundo que o do Paran¨¢. Muito embora n o se tenha observado altera  es significativas na morfologia dos canais entre os per¨ªodos de vazante e cheia, o mesmo n o ocorreu com a textura da carga de fundo: o canal do tribut¨¢rio est¨¢ sofrendo processo de ajoiamento (armoring effect) ligado ao fechamento da barragem de Rosana (1987
%K Mapas batim¨¦tricos
%K Conflu¨ºncia
%K Rio Paran¨¢
%K Rio Paranapanema
%K River confluence
%K Channel morphology
%K Paran¨¢ River
%K Paranapanema River
%U http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S1851-49792009000200004