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

Abstract

Variability in the regional setting and morphology of cuspate forelands on the west coast of Western Australia is examined in this paper. In accordance with this aim, principal differences in the geologic and geomorphologic setting of three prominent sites on the west coast were established and their association with historical changes and contemporary oceanographic processes was examined. The cuspate forelands investigated are Jurien Bay, Winderabandi Point and Turquoise Bay. The most significant differences in geologic setting are associated with the structure and location of an extensive offshore reef system. Morphologically, the reef alters from south to north, changing from a discontinuous ridge parallel to the shore along the central west coast, to a nearly continuous fringing reef at Ningaloo. The reefs vary in distance from the shore, being farthest in the south and closest in the north and they impound a series of inshore basins, or lagoons. The deeper southern basins are dominated by locally generated wind waves and wind-generated currents. The shallower northern basins are most markedly affected by tidal currents and wave pumping across the reef flats.The large cuspate foreland at Jurien on the central west coast has undergone shoreline configuration change in response to changing phases of storminess 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 coast, relict Pleistocene limestone has provided the focus for sedimentation and morphology has been controlled by a balance in refracted wave energy and nearshore currents driven by tidal and wave set-up variability. At Turquoise 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, but its present asymmetrical shape is maintained by strong northerly longshore 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-waveenergy protected environments.

Response of a fringing reef coastline to the direct impact of a tropical cyclone

“…Two subsequent "cyclone recovery" surveys were conducted in October 2015 and June 2016. Although the pre-cyclone survey was conducted 8 months prior to TC Olwyn, there were no significant storms (i.e., TCs) in this period, typical large winter swell events (H sig 4-5 m) have minimal erosion potential ("Model simulations" section), and analysis of historical aerial imagery (from 1969 to 2014) of the Tantabiddi salient using the "Digital Shoreline Analysis System" (Thieler et al 2009) as well as previous work along the greater Ningaloo coastline (Sanderson 2000) provides no evidence to suggest significant seasonal variability in shoreline position (Supporting Information Fig. S1).…”

The dynamics of infragravity wave transformation over a fringing reef

“…These nearshore processes have been identified to be important to many ecological processes within reef environments such as: the control of the spatial distribution of dissolved [ Atkinson and Falter , 2003; Zhang et al , 2011] and particulate [ Yahel et al , 1998; Wyatt et al , 2010] nutrient uptake by reef organisms, ecological zonation [ Dollar , 1982] and larval recruitment pathways [ Roberts , 1997; Kraines et al , 2001]. Furthermore, the physical presence of a reef shapes the nearshore sediment transport pathways [ Storlazzi et al , 2004], controls the associated long‐term morphological changes to a coastline [ Sanderson , 2000], and helps to buffer coasts from extreme forcing events such as hurricanes/cyclones and tsunamis [ Kunkel et al , 2006]. While the importance of some of these nearshore hydrodynamic processes to reef systems is well recognized, the detailed dynamics of many processes still remain poorly understood (certainly in comparison to analogous processes on sandy beach coasts).…”

Australia's temperate carbonate coast: sources, depositional environments and implications

“…These barriers have been partially to wholly submerged by the Holocene sea-level transgression, and now form cliffs, islands, islets and reefs, including extensive shore-parallel barrier reefs. The Pleistocene inheritance has had considerable impact on contemporary coastal processes leading to greater wave attenuation and refraction, resulting in more reef and headland bound beaches, lower-energy beaches and more crenulate beaches (Sanderson 2000;Short 2010b). Cann et al (1999) described the impact of the partly drowned Robe Range on contemporary coastal processes and sedimentation, including the formation of a Holocene marine carbonate-rich corridor between two Pleistocene barrier systems.…”