Morphological Change at the Snowy River Ocean Entrance, Victoria, Australia (1851–2008)

Abstract

Analysis of data, including historical documentation, survey and navigation charts, and aerial imagery, representing a time series of 1851–2008 for the Snowy River ocean entrance area (located in East Gippsland, Victoria, Australia) shows that much morphological change has occurred, including entrance channel migration along 8000 m of Holocene sandy barrier formation. Increasingly frequent episodes of Snowy River entrance channel closure to Bass Strait is apparent from reference to the 1981–2008 record. The deployment of GIS technology allows such long-term coastal zone change to be visualised and documented, and, to some extent, quantified. Explanations for this change relate primarily to altered stream flow regimes. Within the Snowy River catchment, hydrological processes have been irretrievably altered after the development of the Snowy Mountains Hydro-electricity Scheme (SMHS) from 1951, which currently appropriates the vast majority of annual discharge from the high rainfall and snowfall areas of the upper Snowy River catchment. Loss of Snowy River discharge volume in the post-SMHS period also refers to a steady diminution of stream flow yield from the unregulated sub-catchments, due to a reduction in catchment rainfall. Whilst ebb-flow augmentation via stream flow discharge is essential to the maintenance of the Snowy River entrance, both long-term below-average catchment rainfall and snow coverage, together with future climate change predictions, leave provision of legislated flow targets for the lower Snowy River in question. Thus, the Snowy River entrance is likely to remain ephemeral in the future as a direct consequence of inter-regional water transfer and climate change.