Relevance of infragravity waves in a wave-dominated inlet

Type Article
Date 2016-08
Language English
Author(s) Bertin Xavier1, Olabarrieta Maitane2
Affiliation(s) 1 : Univ La Rochelle, CNRS, UMR 7266, LIENSs, La Rochelle, France.
2 : Univ Florida, Dept Civil & Coastal Engn, Gainesville, FL USA.
Source Journal Of Geophysical Research-oceans (2169-9275) (Amer Geophysical Union), 2016-08 , Vol. 121 , N. 8 , P. 5418-5435
DOI 10.1002/2015JC011444
WOS© Times Cited 14
Abstract

This study investigates the relevance of infragravity (IG) waves at Albufeira Lagoon Inlet, a shallow wave-dominated inlet located on the western coast of Portugal. A field experiment carried out in September 2010 revealed the occurrence of low-frequency oscillations (i.e., 25-300 s) in water levels and current velocities. While these fluctuations were present over the ebb-tidal delta along the whole tidal cycle, they only appeared between the beginning of the flood and up to 2 h after high tide inside the lagoon. The XBeach modeling system was applied to Albufeira Lagoon Inlet and reproduced the generation and propagation of IG waves and their blocking during the ebb. This behavior was explained by blocking due to opposing tidal currents reaching 2.5 m s21 in shallow water depths. Numerical results suggest that the breakpoint mechanism and the long bound wave shoaling mechanisms contributed significantly to the generation of IG waves in the inlet. IG waves induced fluctuations in flood currents inside the lagoon reaching temporarily 100% of their magnitude. The fact that these fluctuations occur mostly at flood and not at ebb could promote flood dominance in the lagoon. This hypothesis will have to be verified, namely under storm wave conditions.

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