Sediment Transfer through the Fluvial System (Proceedings of a symposium held in Moscow, August 2004). IAHS Publ. 288, 2004, 165–169

1 Co-operative Research Centre for Catchment Hydrology, PO Box, 1666, ACT 2601, Australia

2 CSIRO, Land and Water, PO Box 1666, ACT 2601, Australia

peter.wallbrink@csiro.au

Abstract In southeastern Australia land-use changes due to European settlement (~180 years ago) triggered widespread channel incision, and erosion from these features delivered massive volumes of sediment to rivers. It is proposed that the channels remain a major source of sediment. We use measurements of ¹³⁷Cs concentrations in soils and sediments to examine sources of fine sediment in incised and un-incised channels. In un-incised channels the ¹³⁷Cs concentrations decreased to around 40–60% of surface hillslope values by stream order 3, whereas the ¹³⁷Cs concentrations in incised channels decreased to 10–15% of surface hillslope values in the 1st order streams. In both cases we attribute the decreases in ¹³⁷Cs concentrations to input of sediment from the channel walls; the input is four times greater in the incised channels. It is concluded that erosion from the walls of incised channels remains a significant source of sediment to rivers in southeastern Australia.

Key words catchment management; channel bank erosion; Cs-137; deposited sediments; gully erosion; land-use change