Modelling sources of sediment at sub-catchment scale: An example from the Burdekin catchment, North Queensland, Australia

Abstract

A detailed sediment budget has been derived for the Weany Creek sub-catchment (13.5 km 2) in North Queensland, Australia, using a sediment source, transport and depositional model known as SedNet (I. Prosser, P. Rustomji, W. Young, C. Moran, A. Hughes, CSIRO Land and Water Technical Report 15/01, Constructing River Basin Sediment Budgets for the National Land and Water Resources Audit, 2001, http://www.clw.csiro.au/publications/technical2001/tr15-01.pdf.). In this study, we have applied SedNet at a much finer scale than it has been applied previously in order to determine sources and sinks of sediment at a scale suitable for grazing land management. We have been able to show that a model such as SedNet can be applied to finer scales (with scale-appropriate modifications to inputs) and in so doing provide insight into sources and sinks of sediment at sub-catchment or paddock scale. The Weany Creek model has been able to show in detail which stream sections (or their associated watersheds) contribute most to suspended sediment loads, as well as where bedload deposits are most likely to accumulate. Additional detail regarding whether erosion is derived from hillslope, or combined gully/bank erosion, or both, has provided valuable insight into the sub-catchment-scale dynamics of erosion. The Weany Creek model has been also used to determine the impact of changes in management practice on sediment erosion, transport and accumulation. A scenario with reduced stocking rates was shown to reduce the delivery of sediment to stream, and consequently led to a lower delivery of fine sediment to downstream reaches.