Broad-scale geomorphology and benthic habitats of the Perth coastal plain and Rottnest Shelf, Western Australia, identified in a merged topographic and bathymetric digital relief model*

Abstract

A digital relief model (DRM) of the Swan Coastal Plain and Rottnest Shelf (7400 km2) was built with a range of topographic and high-resolution bathymetric datasets, gridded to a 50 m cell size. The DRM enabled the delineation of relict coastal landforms, benthic habitats and development of a regional morphostratigraphic framework. Well-defined features include: (1) limestone ridges on the coastal plain that sit subparallel to the modern shoreline and were largely formed as coastal dune barriers during or shortly after Quaternary interglacial periods of high sea level; (2) rocky reefs on the inner shelf that rise up to 10 m above the adjacent seafloor, which are remnants of coastal dune barriers that formed when the sea level was 20–30 m lower than present and (3) a discontinuous ridge 3–10 m high along much of the outer shelf, which likely represents a coastal barrier that formed when the sea level was around 60 m lower than present. The DRM provides a useful regional perspective of the distribution and form of these extensive reefs.