Geocoastal Research Group
The University of Sydney
Anna Helfensdorfer is a PhD candidate of the Geocoastal Research Group at the University of Sydney. Her project will assess the theory of the recent geomorphic and geologic evolution of the Murray River channel and sedimentation in the lower Murray Gorge. This will be achieved through a complementary analysis of sediment cores and hydrological modelling. A primary hypothesis of her study is to determine the plausible palaeoenvironmental conditions which led to the deposition of a finely laminated clay sequence within Lake Alexandrina and the lower Murray Gorge during much of the Holocene. Specifically, her study seeks to assess whether a blockage, constriction or virtual blockage by sea level at the Murray Mouth allowed for this depositional setting.
Through collection, examination and dating of sediment cores taken from the lower Murray River and its floodplain, the extent and development of this laminated clay sequence will be determined. Radiocarbon dating will be conducted to determine the timing of the establishment of lacustrine-estuarine conditions and the late Holocene transition to, and development of, the present day riverine channel.
The hydrological model TUFLOW FV will be used to assess the geomorphic response of the lower Murray River, lower lakes and the Coorong to sea level fluctuations during the Holocene. Multiple model domains will be developed to represent key snapshots in the geomorphic evolution of this lacustrine-estuarine system. Sensitivity analyses will be conducted to develop a range of plausible geomorphic responses relative to fluvial discharge, sea level, wind and tidal regimes and the resulting flow velocities will be analysed to determine the likelihood of preservation of primary sedimentary structures. The outcome of her study will be a revised model of the geomorphic history of the lower Murray River and its estuary.