Efeitos marinho e fluvial na dinâmica dos ambientes inundáveis do Estuário Superior do Rio Pará, Norte do Brasil

Abstract

In coastal regions, flood plain environments occur in the lower course of rivers and their tributaries, where the daily flooding cycle controlled b ytides results in hydrodynami cconditions of considerable complexity. On the north coast of Brazil, close to the Tocantins-Maratauíra System (STM), in the Pará River Estuary, the flooding environments present physical characteristics such as insular geography in a sheltered continental sector, an intense fluvial discharge, and a tidal range upto 6 m. In order to understand how the floodplain environments of this estuary are affected by tides, this study performed amulti proxy approach (hydrodynamics, topography, vegetation, morphology, superficial sedimentary cover) for the delimitation of the Pará River Estuaryinz on esand for the investigation of the flood plain environments of the STM, correlating the mtothe corresponding estuarinezone. From the results achieved, three flood plain environments and anon-floodable one were recognized. These environments integrate the Pará River Upper Estuary, and have their flooding cycle controlled by tides with a mesotidal range. On the other hand, due to the high fluvial discharge, the ecological landscape essentially consists offreshwater ecosystems. It can be concluded from the results that the environments most vulnerable to flooding are in theinterval between 0 and 3 m and represent 39% of the insular region. However, the highest occurrence of those environmentsis found in the southern sector (40.6%), landward-directed, which highlighted the dynamic and more unstable nature of thisarea when compared to the northern sector (21.1%), seaward-directed. It can be observed that the tide is one of the major forcings of local hydrodynamics, leading to the conceptual definition of the courses integratedin to the ST Mdrainagenet work compatible as tidal rivers. The results provide a better understanding of the morphodynamics of the modern landscape andexposeits vulnerability, taking in to accountits human occupation.