The application of fallout radionuclides to determine the dominant erosion process in water supply catchments of subtropical South‐east Queensland, Australia. Issue 6 (6th July 2012)

• Record Type: Journal Article
• Authors: Olley, Jon; Burton, Joanne; Smolders, Kate; Pantus, Francis; Pietsch, Timothy; Walling, Des E.; Golosov, Valentin; Olley, Jon
• Is Part Of: Hydrological processes. Volume 27:Issue 6(2013:Mar. 15)
• Page Start: 885
• Page End: 895
• Publication Date: 2012-07-06
• Subjects: Hydrology -- Periodicals; Hydrology -- Research -- Periodicals; Hydrologic models -- Periodicals; Hydrological forecasting -- Periodicals; 631.432
• DOI: 10.1002/hyp.9422
• Languages: English
• ISSNs: 0885-6087

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>Previous studies using fallout radionuclides (<sup>137</sup>Cs and <sup>210</sup>Pb<sub>ex</sub>) to determine the relative contributions of surface‐soil and channel erosion (including gullies and channel banks) to stream sediments have used a relatively small number of composite samples (<25) to characterize the source end members, and concentrations in each of the source end members have, through the use of means and standard errors, been assumed to be normally distributed. Here, we examine <sup>137</sup>Cs activity concentrations to determine the erosion processes supplying sediment in seven water supply catchments in South‐east Queensland. First, we test some of the underlying assumptions in the method using concentrations of <sup>137</sup>Cs and <sup>210</sup>Pb<sub>ex</sub> in composite samples collected from 109 surface‐soil sites and 39 channel‐bank sites. Paired composite samples, each consisting of 20 subsamples, from five sites are used to demonstrate that this sampling approach was sufficient to average out any local variations in surface‐soil <sup>210</sup>Pb<sub>ex</sub> and <sup>137</sup>Cs concentrations across the 300 m<sup>2</sup> sampled. We derive probability distributions for <sup>137</sup>Cs and <sup>210</sup>Pb<sub>ex</sub> concentrations in the group of samples from each of the end members and show that only the distribution of <sup>210</sup>Pb<sub>ex</sub> in samples from surface soils is normally distributed. We use the probability distributions for <sup>137</sup>Cs, which provides the greatest discrimination between sources, to show that the <sup>137</sup>Cs concentrations on the river sediment samples are consistent with channel erosion being the dominant source. Conservation works aimed at reducing the supply of sediments in these catchments should therefore focus on rehabilitation of the channel network and decreasing the runoff to the channel network. These findings are consistent with other similar studies on tropical Australian rivers. Copyright © 2012 John Wiley & Sons, Ltd.</p> </abstract>