UTILIZATION OF TOPOGRAPHIC ANISOTROPY FOR ASSESSMENT AND DETECTION OF RIP CHANNELS

Rip currents are common in coastal environments and represent a relatively high-velocity flow of water away from the beach. As beach morphology adapts to sediment fluxes and wave climate, it is essential to be able to identify and assess rip current locations and their evolution. Furthermore, it is essential to be able to characterize the scale-dependent bathymetric morphology that governs the extent and relief of a rip channel. Consequently, our primary objective is to assess the nature of the scale-dependent topographic anisotropy, in order to identify rip current locations in coastal environments. Specifically, we utilized multi-band satellite imagery to generate a bathymetric digital elevation model (DEM) for Bondi Beach Australia, and collected field data to support our analysis. Scale-dependent spatial analysis of the DEM was conducted to assess the directional dependence of topographic relief and the magnitude of topographic anisotropy. We used geovisualization of ellipsoids and graphed anisotropy parameters to examine the morphological conditions of beaches and rip channels. Our preliminary results indicate that rip channels generally have a higher anisotropy index and orthogonal orientation compared to shoreline anisotropy and orientation. Scale-dependent variations in anisotropy can be used to assess the spatial extent of rip channels. These results clearly reveal that well-developed rip channels can be identified and assessed using topographic anisotropy, as scale-dependent anisotropy patterns are unique when compared to the surrounding bathymetry and terrain. In this way, it is possible to evaluate rip channel morphology and frequency along the coast. In future work, we will generate anisotropic parameter images that can be used to depict the spatial location of well-defined rip channels.