THE INFLUENCE OF CALCARENITE LIMESTONE REEFS ON BEACH EROSION AND RECOVERY, FROM SECONDS TO YEARS

Abstract

Mechanisms through which natural rock and coral landforms interact with waves, currents, sediment transport and beach morphology are still poorly understood. Therefore, interactions between sediment transport and calcarenite limestone landforms at Yanchep Lagoon in southwestern Australia were investigated over a cascade of spatial and temporal scales: from single waves, through sea breeze and storm events, to seasonal and inter-annual variability. The hypotheses that were confirmed included: (1) hard landforms with higher elevations relative to sea level are more likely to reduce beach erosion but also to inhibit recovery; and (2) the placement and continuity of landforms in the nearshore can generate current jets, and hence local sediment sources and sinks. These hypotheses were consistently confirmed at all scales, however results show that to fully explain changes at broader scales (such as inter-annual and seasonal changes) an understanding at finer scales (such as during sea breezes, storm event and single waves) was necessary.