Standing longwave formations in reef-lagoon bathymetries: Fid-Bau Portal

Standing longwave formations in reef-lagoon bathymetries

Bheeroo, Vivek A. / Yeh, Harry

Abstract Standing longwave formations are investigated in the presence of a broad submerged sill off the vertical reflective wall: this configuration represents a model of reef-lagoon formations often present in coral-reef coasts. A series of laboratory and numerical experiments are performed for the waves of which wavelengths are comparable to the bathymetry length scale. The results reveal that the wave amplitude at the reflective boundary wall can surpass the case without the presence of the reef. Adverse wave conditions are also observed in the reef-lagoon span when the waves are longer than the reef breadth. Enhancement of the higher harmonics of the waves is seen inside the lagoon. The present experimental results highlight the potential that the presence of an offshore reef could worsen the wave climate in the nearshore region behind the reef for the case of standing longwave formations. The zone of influence of the reef is however localized to the lagoon and the reflective wall extent, while the offshore standing wave formation remains minimally influenced except for the phase shift in the standing-wave envelope.

Highlights • Cnoidal wave-induced standing waves are investigated across a broad submerged sill adjacent to a wall. • This configuration is a model for a reef-lagoon system presented in the tropica; islands. • The reef causes the enhancement of higher harmonic components, resulting in a complex and energetic wave field in the lagoon. • For sufficiently long waves, there is a worsening of the nearshore wave climate due to the presence of a broad reef.