Anatomy of a floodout in semi-arid eastern Australia
Redgum Rise is an intermediate floodout (sensu TOOTH 1999) along an anabranch of Faulkenhagen Creek, in the Wannara Creek catchment in semi-arid western New South Wales. Australia (30°51'S, 143°12'E). We document the morphology, geomorphology and sediments of this floodout, and infer its genesis via observations of the deeper sedimentary record, its history over 39 years of aerial photography and ten years of measurement, and its responses to an extraordinary set of storms which include the 1:320 year daily rainfall. We conclude that the floodout is self-propagating as a fine-grained, upstream migrating channel plug with associated sandy wedge-like deposits atop the floodplain surface. Drainage breakdown and resultant floodout sedimentation is the most prominent form of alluvial sedimentation in the catchment, and creates the most likely of longer-lived sedimentary units. A basin-fill model of floodout sedimentation is proposed, based on observed patterns of deposition and material reworking at and around Redgum Rise.
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