Tide-modulated wave characteristics and breaking regimes in the intertidal zone of a dissipative beach

Abstract

Waves propagating on sandy beaches are naturally affected by tides. A better understanding of tide-modulated wave characteristics and breaking regimes in the intertidal zone is important for beach protection and disaster mitigations. Here, field measurements are conducted in the intertidal zone on a dissipative beach. Wave characteristics are found to be highly modulated by changing tidal levels. Waves in the intertidal zone is depth-controlled within water depths of 3 m. Measured wave data are used to verify and evaluate parametric wave breaking dissipation models. The model accounting for the ratio of wave height to depth which is neglected previously provides the best predictions. The breaking regimes change during a tidal cycle. The breaking dissipation is more rapid at low to medium tidal levels and the wave breaking is more saturated at medium to high tidal levels. This is because the region for breaking dissipation is highly modulated by tidal levels. Finally, it is found that the breaking dissipation should be large enough in relatively deep water to maintain a constant wave height to depth ratio in the intertidal zone, implying the previous definition of depth-limited breaking seems too strict for the present case.