Abstract
Estuarine processes are directly related to the interaction of its forcing conditions with the local morphology. In this study we assess the implications of the opening of a new inlet on the hydrodynamics and suspended sediment concentration (SSC). A set of physical parameters have been measured in the Itanhém river estuary, a small, shallow and mangrove fringed tropical estuary in Northeastern Brazil. Field surveys have been conducted in August 2007 and January 2008, separated by an important morphological change. Our observations show that even shortening the lower estuary channel in 2 km, the inlet opening did not imply in changes in the estuarine circulation. However, SSC increased after the inlet opening. General estuarine circulation showed synodical modulation of tidal asymmetry and residual suspended sediment transport. The estuary showed flood dominance at spring tide and ebb dominance at neap tide. Although not directly changing the estuarine hydrodynamics, the morphological change resulted in an important increase in SSC. This increase might be related to a facilitated import of inner shelf sediment through a shorter channel, having important implications for the estuarine sedimentation processes.
Highlights
Estuaries are aquatic environments in the continentocean interface where the marine and river water interact with each other
Stationary Sampling Station this paper we present an assessment on the estuarine hydrodynamics comparison between two distinct situations: i. when the inlet is located further south, with an approximately 2 km longer lower estuarine channel; and ii
In order to present the main differences between both surveys, conducted under different morphological settings, results are presented in a comparative manner, with 2007 (Figures 3 and 4) representing the longer estuarine channel and 2008 (Figures 5 and 6) the post spit breaching situation
Summary
Estuaries are aquatic environments in the continentocean interface where the marine and river water interact with each other. They are semi-enclosed coastal water bodies, with one or more connections with the open sea, where the sea water mix in different ratios with fresh water from the drainage. The tidal asymmetry is the result of non-linear processes, which produces higher frequency tidal constituents of the astronomical tides and can generate flood or ebb dominance (Dronkers 1964, Speer and Aubrey 1985). In ebb dominated systems the ebb phase is shorter than flood phase, sediment is efficiently transported seawards, and the geometric configuration is usually stable (Speer and Aubrey 1985, Aubrey 1986, Friedrichs and Aubrey 1988)
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