Sedimentary Dynamics in the Piraquê-Açu Estuarine System - Aracruz / ES

Name: Rodolfo Teixeira Alves
Type: MSc dissertation
Publication date: 16/07/2018

Namesort descending Role
Valéria da Silva Quaresma Advisor *

Examining board:

Namesort descending Role
Alex Fabiano Jardim Internal Examiner *
Marcos Nicolás Gallo External Examiner *
Valéria da Silva Quaresma Advisor *

Summary: Estuaries are coastal environments of enormous environmental, social and economic importance. In the context of sedimentary dynamics, these environments act primarily as sediment exporters to the platform, but in some situations they may also import material into the system. Among the main estuaries in the state of Espírito Santo, the Piraquê-Açu and Piraquê-Mirim Estuary System (SEPAPM) stands out because it has the largest mangrove area in the state (Barroso, 2004). Many articles focus on the biological, chemical, physical and sedimentological characteristics of this environment (Barroso, 2004, Neves, 2010, Melado, 2011, Leite, 2012, Silva and others, 2013, Monteiro, 2015, among others). However, there is still little information on SEPAPM's sedimentary dynamics. In this way, the main objective of this work is to estimate the total sedimentary balance in the lower section of the estuary under different tidal conditions (syzygy and quadrature) and river flow (dry and rainy period), as well as to evaluate its sedimentary contribution to the platform . Using data collected in situ from current, temperature, salinity and suspended particulate matter, the hydrodynamic behavior within the estuarine system was analyzed, as well as the quantification of the total sediment load transported through the bottom loading and suspended load equations proposed by Van Rijn (2007). In general, the estuary presented a poor stratification of the water column, characterized, therefore, by a process of mixing by turbulent diffusion. This fact was observed by calculating the number of Richardson per layer (RiL), whose values ​​were lower than 20. The exception was the north arm of the estuary (Piraquê-Açu river), which during the quadraturas presented the formation of a salt wedge and RiL greater than 20, being characterized by the dominant entining process (entrainment). In relation to the sedimentary balance, the estuary behaved as exporter of sediment in almost all the campaigns carried out, except for the period of rainy season, WHERE there was sediment import. The transport of suspended cargo was superior to the transport of bottom cargo in all the analyzed campaigns, and the periods of syzygy presented higher transport volumes in relation to the quadrature periods. Annually, it is estimated that SEPAPM is responsible for exporting approximately 10.5 tons of sediment to the platform.

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