Beach Response to Variations in Breaker Height

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Abstract
The breaker wave height required to produce a particular beach-surfzone morphology is examined for micro-tidal, medium to fine sand beaches. Waves >2.5m produce dissipative beach systems with wide surfzones and shore parallel bar/s and channel/s. Breakers between 1 and 2.5m result in rip circulation and associated rhythmic morphology (crescentic bars, rip channels, megacusps, etc). Low waves (<lm) form steep, barless reflective beaches with characteristic cusps/berm. To gauge the stability/mobility of each of these beach types the range of beach profile changes associated with each is presented, for both the time and space domain. Modally dissipative beaches where breakers consistently exceed 2.5m undergo minor changes in profile and are consequently stable both temporally and spatially. Modally rhythmic beaches have a variable moderate energy wave climate are highly unstable both over time and alongshore. Modally reflective beaches with their low waves are relatively stable. Beaches which experience a highly variable wave climate over time exhibit all three types and are consequently highly unstable. The environmental parameters useful for quantifying these beach types and associated profile changes, and the implications of these results are discussed.

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