Morphology of the Wide Bay Inlet ebb-tidal delta, 1987-2009, as observed through Landsat 5 and Landsat 7 imagery: a multidecadal analysis of ebb delta morphological variation using optical satellite imagery derived nearshore topographies

The morphology of ebb-tidal deltas, found on the seaward side of tidal inlets, is shaped by the relative strength of tide and wave generated currents, frequency and intensity of storms and overall sediment supply within the coastal compartment. In micro-tidal environments, ebb tidal deltas are predominantly below the low water mark, and so detailed observational studies of morphological evolution have been hampered by the difficulties in obtaining regular time series benthic terrain data in the near shore zone. The aim of this study is to investigatethe evolution of the ebb-tidal delta at the Wide Bay Inlet from 1987 to 2009. Benthic surfaces for each year were derived from relative depth values generated by implementing a ratio transform algorithm developed by Stumpf et al. (2003), based on the differential attenuation of light at blue and green wavelengths as a function of depth. Changes between the resultant relative depth surfaces evidence movement of the morphological elements of the ebb-tidal delta complex as well as patterns of sediment movement onto the shoreline and associated patterns of shoreline progradation and erosion. Spatial variability of the main ebb-tidal elements and the periodicity of these variations are documented and compared to conceptual models of ebb-tidal delta behaviour.