Sediment sources in a dry-tropical catchment: central Queensland, Australia.

Rivers draining into the Great Barrier Reef lagoon are receiving increased attention from catchment managers and scientists, with the realisation that European land use changes over the last ∼150 years may have increased river sediment yields with resultant adverse effects on the receiving marine environment. Mitigation of the effects associated with such changes is only possible if information on the spatial provenance and dominant types of erosion is known. This study uses fallout radionuclide ( 137 Cs and 210 Pb ex ) and geochemical tracing of river bed sediments to examine sediment sources for Theresa Creek, a subcatchment of the Fitzroy River basin, central Queensland, Australia. Sheetwash and rill erosion from cultivated basaltic land and channel erosion from non-basaltic parts of the catchment were found to be contributing most sediment to the river system. Evidence indicates that the dominant form of channel erosion is gully head-cut and sidewall erosion. Sheetwash and rill erosion from uncultivated land (i.e. grazed pasture/woodland) is a comparatively minor contributor of sediment to the river network. Due to the limited extent of cultivation, on a basin-wide scale, channel sources are likely to be the largest contributor of sediment to the Fitzroy River basin; accordingly catchment managers should focus their efforts on reducing the sediment yield from these sources.