Supply limited sediment transport in a high‐discharge event of the tropical Burdekin River, North Queensland, Australia

Abstract

Interactions between catchment variables and sediment transport processes in rivers are complex, and sediment transport behaviour during high‐flow events is not well documented. This paper presents an investigation into sediment transport processes in a short‐duration, high‐discharge event in the Burdekin River, a large sand‐ and gravel‐bed river in the monsoon‐ and cyclone‐influenced, semi‐arid tropics of north Queensland. The Burdekin's discharge is highly variable and strongly seasonal, with a recorded maximum of 40 400 m3 s−1. Sediment was sampled systematically across an 800 m wide, 12 m deep and straight reach using Helley‐Smith bedload and US P‐61 suspended sediment samplers over 16 days of a 29‐day discharge event in February and March 2000 (peak 11 155 m3 s−1). About 3·7 × 106 tonnes of suspended sediment and 3 × 105 tonnes of bedload are estimated to have been transported past the sample site during the flow event. The sediment load was predominantly supply limited. Wash load included clay, silt and very fine sand. The concentration of suspended bed material (including very coarse sand) varied with bedload transport rate, discharge and height above the bed. Bedload transport rate and changes in channel shape were greatest several days after peak discharge. Comparison between these data and sparse published data from other events on this river shows that the control on sediment load varies between supply limited and hydraulically limited transport, and that antecedent weather is an important control on suspended sediment concentration. Neither the empirical relationships widely used to estimate suspended sediment concentrations and bedload (e.g. Ackers & White, 1973) nor observations of sediment transport characteristics in ephemeral streams (e.g. Reid & Frostick, 1987) are directly applicable to this river.

Predicting suspended sediment concentrations in the Meuse river using a supply‐based rating curve

“…Linking SSC to a hydraulic parameter using a rating curve mostly results in a large scatter of observations around the rating curve (Al-Ansari et al, 1988;Amos et al, 2004;Bogen, 2004). Also, the Q -SSC relation often shows considerable hysteresis effects (Asselman, 1847(Asselman, 1997Picouet et al, 2001;Morehead et al, 2003;Bogen, 2004).…”

“…Predicting SSC from Q using a rating curve, therefore, generally results in poor predictions of SSC in the course of flood events, and may even result in poor estimates of annual budgets. It has been widely recognized that SSC is controlled by the amounts of sediment supplied from upstream parts of a catchment, and by the timing of suspended sediment supply from different tributaries to the lower reaches in larger river basins ( (Bogen 1980;Webb, 1981, 1982;Spott and Guhr, 1994;Asselman, 1997;Morehead et al, 2003;Amos et al, 2004;Moliere et al, 2004). Exhaustion of sediment supply from the upstream basin is generally seen as a major cause of clockwise hysteresis in the Q -SSC relation (Asselman, 1997).…”

An experimental test of the effects of inorganic sediment addition on benthic macroinvertebrates of a subtropical stream

“…These parameters can modify the effect of sediment on aquatic ecosystems (Culp et al, 1986;Carvalho, 1994;Francoeur & Biggs, 2006). High sediment loads are associated with high discharge events, and some studies found a linear relationship between flow and suspended sediment concentration (Amos et al, 2004). High flows during spates, and the associated increase in sediment transport, usually reduce density of benthic organisms (Melo et al, 2003a;Bond & Downes, 2003).…”

“…Transport of sediment is dependent upon hydraulic parameters, such as flow, streambed slope, and the local bed composition (Wood & Armitage 1997;Amos et al, 2004). These parameters can modify the effect of sediment on aquatic ecosystems (Culp et al, 1986;Carvalho, 1994;Francoeur & Biggs, 2006).…”

Bottomset Architecture Formed In the Troughs of Dunes and Unit Bars

“…Discharge events, caused by monsoon rain or tropical cyclones, rise rapidly to a peak up to three orders of magnitude larger than base flow and then decline almost as quickly (Alexander et al 1999;Amos et al 2004). …”