Browsing by Author "Mann, RA"

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    Assessing soil remobilisation in catchments using a 137Cs-sediment hillslope model
    (Taylor & Francis (Routledge), 2008-12) Simms, AD; Woodroffe, CD; Jones, BG; Heijnis, H; Harrison, JJ; Mann, RA
    Soil redistribution studies are important, especially in water supply catchments, because the rate at which denudation is occurring has implications for offsite water quality. However, the extent to which soil is redistributed within the landscape can be difficult to determine. This challenge can be overcome using fallout caesium-137 (137Cs). This paper describes the rates of soil loss and remobilisation in two sub-catchments within the Sydney Basin region, namely Kembla and Kentish Creeks, which drain to the Cordeaux reservoir. The total inventories of 137Cs in catchment soils were determined, a 137Cs-regression equation and a theoretical diffusion and migration model were used to established relationships between 137Cs inventories and the rates of soil loss. These relationships revealed relatively low occurrence of soil loss in Kentish Creek, but two slopes in the Kembla Creek sub-catchment had losses that appear to be moderate. However, there was no clear evidence to suggest whether slopes in upper and lower reaches of catchments had specific patterns of soil remobilisation. Qualitative categorisation of the slope elements using a 137Cs-sediment hillslope model can be a useful sentinel for land users and decision makers even if absolute rates of soil loss or gain are not certain. The findings suggest that sediments mobilised in the study sub-catchments are not likely to impact significantly on the water quality in the Cordeaux reservoir. © 2008, Taylor & Francis (Routledge).
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    Use of Pb-210 and Cs-117 to simultaneously constrain ages and sources of post-dam sediments in the Cordeaux reservoir, Sydney, Australia
    (Elsevier, 2008-07) Simms, AD; Woodroffe, CD; Jones, BG; Heijnis, H; Mann, RA; Harrison, JJ
    Environmental radionuclides can be employed as tracers of sediment movement and delivery to water bodies such as lakes and reservoirs. The chronologies of sediments that have accumulated in the Cordeaux reservoir in Sydney, Australia, were determined by the rate of change of Pb-210(cx) with depth and indicate slow accretion in the reservoir. The ratio of enrichment of radionuclides in sediment cores to Pb-210(cx) and (CS)-C-117 concentrations in a reference soil sample within the Cordeaux catchment indicates that the dominant source of sediment in the Cordeaux reservoir is surface erosion (detachment and removal of sediment at depths less than 30 cm). However, in the Kembla Creek arm of the reservoir a mixture of sources was detected and includes sheet and rill erosion together with sub-soil contributions. Implications for the utility of these radionuclide sedimentation assessments, especially where samples are limited, are that well-constrained chronologies and sources of soil erosion are facilitated. © 2008, Elsevier Ltd.