A comparison of reef-protected environments in Western Australia: The central west and Ningaloo coasts

Variability in the regional setting and morphology of cuspate forelands on the west coast of Western Australia is examined in this paper. In accordanc e with this aim, principal differences in the geologic and geomorphologic s etting of three prominent sites on the west coast were established and thei r association with historical changes and contemporary oceanographic proces ses was examined. The cuspate forelands investigated are Jurien Bay, Winder abandi Point and Turquoise Bay. The most significant differences in geologi c setting are associated with the structure and location of an extensive of fshore reef system. Morphologically, the reef alters from south to north, c hanging from a discontinuous ridge parallel to the shore along the central west coast, to a nearly continuous fringing reef at Ningaloo. The reefs var y in distance from the shore, being farthest in the south and closest in th e north and they impound a series of inshore basins, or lagoons. The deeper southern basins are dominated by locally generated wind waves and wind-gen erated currents. The shallower northern basins are most markedly affected b y tidal currents and wave pumping across the reef flats. The large cuspate foreland at Jurien on the central west coast has undergon e shoreline configuration change in response to changing phases of stormine ss as well as in response to a change in focus for sediment deposition as a result of offshore reef erosion. At Winderabandi Point on the Ningaloo coa st, relict Pleistocene limestone has provided the focus for sedimentation a nd morphology has been controlled by a balance in refracted wave energy and nearshore currents driven by tidal and wave set-up variability. At Turquoi se Bay, where the lagoonal basin is most shallow and narrow, the morphology of the foreland suggests that it may at some stage have been migratory, bu t its present asymmetrical shape is maintained by strong northerly longshor e drift and strong currents exiting the lagoon through a nearby gap in the reef crest. Fundamental differences between the two coastal regions include the structure of the offshore reef, processes driving flow of water within the lagoons and the role of storminess in evolution of coastal landforms. Although many questions regarding storm surge dynamics and landform change remain unanswered, this research provides a significant contribution to the understanding of the evolution of morphological systems in low-wave-energy protected environments. Copyright (C) 2000 John Wiley & Sons, Ltd.