Influence of Offshore Reefs on Low-Frequency Waves During Harbor Resonance

In this paper, a fully nonlinear Boussinesq model is used to simulate the shoreward propagation of bichromatic wave groups over different fringing reef topographies and the subsequent low-frequency oscillations inside a harbor. Based on a low-frequency wave separation technique, the effects of the reef-face slope and the reef ridge on the bound and free long waves inside the harbor and their relative components under the condition of the lowest resonant mode are systematically investigated. For the given harbor, the given reef ridge and the range of the incident short wave amplitudes and the reef-face slopes studied in this paper, results show that the amplitude of the free long waves inside the harbor increases with the reefface slope, while the bound long waves inside the harbor is insensitive to the variation of the reef-face slope. The existence of the reef ridge can notably restrain the bound long waves inside the harbor when the incident short wave amplitudes are large, while it has little influence on the free long waves inside the harbor.