| Abstract | The Ningaloo Reef is a fringing reef, which dominates part of the Gascoyne coast in the North West of Australia. It forms 280 km of segmented, narrow reef crests and lagoons. Reef morphology has dictated terrestrial and lagoonal sedimentation during the Quaternary. The reef supports a wide variety of important habitats and is of worldwide conservation and biodiversity significance. The value of the area has been recognised by establishment of the Ningaloo Marine Park and Cape Range National Park. The coastal plain adjacent to the reef is situated within the Carnarvon Basin and the regional geology is dominated by Late Tertiary to Late Cretaceous limestone anticlines, including raised reef terraces, which are expressed as the Cape and Giralia Ranges.
The dominant physical processes responsible for Quaternary coastal evolution and continued modification of the coastal system are: sealevel variations, oceanography and present and past climate. The Leeuwin and Ningaloo currents are the dominant regional currents in this area. The lagoonal current system consists of northerly long shore drift, wave-pumped influx over the reef crest, and lagoonal flushing through reef passes.
The Holocene evolution of the coastal plain adjacent to the Ningaloo Reef occurred in five stages; shelf erosion and shore face retreat, transgressive deposits, highstand deposits, regressive deposits and modern beach and foredune development. The first four stages are a direct response to Late Holocene sealevel variation, and the last is a consequence of the modern sedimentary system. A distinctive stratigraphy has developed as a reflection of these influences, with large parabolic dune fields deposited during transgression and highstand, relic coastal features (cliffed shorelines, emergent marine embayments and relic-foredunes) generated during highstand and beach ridge plains formed during regression.
Limestone headlands, stranded marine embayments and an expansive Pleistocene desert dune plain dominate the regional geomorphology. The coastal plain in mapped areas is characterised by a limestone hinterland with a thin colluvial cover, adjacent to a narrow coastal strip of Holocene dunes, including sequences of linear dunes plains and relic-foredunes, large parabolic dune fields, and both rocky/cliffed and sandy shorelines. Significant degradation of this fragile environment occurs despite some land and tourist management strategies put in place. Degradation is associated with nodes of activity, where access track development has the greatest impact due to uncontrolled networks of tracks.
Geomorphological mapping of the coastal zone provided a regional data base, which was analysed in terms of natural, and anthropogenic coastal environmental impacts, plus the development of a land classification scheme based on substrate capability. Land system units (geological units, further defined by environmental characteristics) with low substrate capability are unconsolidated, commonly mobile units, with little to no vegetation cover over steep slopes and undulating topography, making them prone to sediment remobilisation. Land system units with a medium to high substrate capability consist of consolidated limestone with a thin to non-existent cover of colluvial, material and significant vegetation cover. The delineation of risk zones, based on GIS analysis identified areas of land particularly at risk of degradation due to a combination of substrate characteristics and level of land use. This study is useful for land management purposes as it quantifies the impacts on the coastal zone and allows for the development of more effective management strategies. A major review of land management practices in the region is currently being undertaken by government agencies, and the environmental data produced in this study will be of direct assistance. |
