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Tidal Inlets Hydraulics and Morphological Modeling: An application to Mundaú Lagoon, Brazi

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Author

  • Almir Nunes De Brito Junior

Summary, in English

Tidal inlets are narrow channels connecting coastal lagoons to the sea and in this way controlling the exchange of water while serving as navigational pathways. These important components of the coast are also very dynamic environments, having their morphology determined by multiple sediment transport processes, making tidal inlets difficult to model. Expected future sea level rise imposes an added challenge to the management and maintenance of the inlets and also of the connected lagoons, in particular for poorly studied regions that often lack data to support more detailed morphological models. The present thesis advances the development of new numerical and analytical models to be used in preliminary studies and to serve as useful tools for qualitative and quantitative assessment of tidal inlet hydraulics and morphology. The study validated the developed approaches against a natural and dynamic inlet-lagoon system: the Mundaú Lagoon (northeastern Brazil). Furthermore, the research investigated internal processes of this lagoon that are affected by the flow through its inlet, such as the water exchange, during the critical dry season scenario, and the impacts of the tidal exchange on the lagoon salinity dynamics and population of its characteristic mussels. A semi-analytical approach was developed based on the classical Keulegan equations, resulting in a series of expressions in non-dimensional form, describing key characteristics of the inlet flow as the lagoon levels response to tides, tidal prism, and inlet velocities, having as the main independent variable the repletion coefficient. These flow expressions were then used in a sediment balance equation for the inlet evolution resulting in diagrams of inlet equilibrium for different scenarios related to inlet geometry configurations. The numerical model for the inlet morphology was applied in the Mundaú lagoon inlet long-term (decadal) and validated through schematic simulations and an application to a complex set of forcing conditions. In this way, the inlet evolution was estimated through the evolution of the inlet width, based on a geometrically similar idealization of the cross-section. The approach taken resulted in a satisfactory description of the inlet evolution through fast simulations and showing potential for long-term assessment of the inlet morphology. In conclusion, the developed models demonstrated the ability to reproduce the main characteristics of the inlet flow and morphological evolution, requiring only key information about the inlet and lagoon geometries as well as the main forcing. Furthermore, the fast execution times required by the numerical model is promising for applications in a probabilistic manner exploring multiple future scenarios

Publishing year

2020-04-28

Language

English

Document type

Dissertation

Publisher

Water Resources Engineering, Lund University

Topic

  • Engineering and Technology
  • Oceanography, Hydrology, Water Resources

Keywords

  • Tidal inlets
  • Numerical modeling
  • Coastal lagoons
  • Mundaú Lagoon
  • Sururu
  • Sediment transport

Status

Published

Supervisor

ISBN/ISSN/Other

  • ISBN: 978-91-7895-500-8
  • ISBN: 978-91-7895-501-5

Defence date

5 June 2020

Defence time

10:15

Defence place

Lecture hall V:B, building V, John Ericssons väg 1, Faculty of Engineering LTH, Lund University, Lund. Follow via Youtube: https://youtu.be/tBE_EZsrjRQ

Opponent

  • Jose A. Jimenez (Prof..)