High-Frequency Water-Level Oscillations in a Semi-Enclosed Embayment

Two types of high-frequency water-level oscillations, wind waves and gravity waves in Batemans Bay, New South Wales, Australia, were analyzed by observed water-level and significant wave height data combined with numerical modelling output. The high-frequency wind waves were closely correlated with the tidal-depth change, giving strong evidence of wave–tide coupling and its phase-locked manner. This was supported by modelling the effect of bottom friction induced by a sandbar southeast of the water-level measurement site. The lower-frequency quarter wave, a type of gravity wave, oscillated across the whole bay. Its frequency of approximately 1 h was close to the theoretical value based on the bay dimensions. The topographic and geometric settings of the bay are the principal reasons for the characteristics of these waves. This observation has significant implications for the bay–shelf water exchange and induced hydrodynamics in similar embayments elsewhere in the world.