Sediment source changes over the last 250 years in a dry-tropical catchment, central Queensland, Australia

Hughes, Andrew O.; Olley, Jon; Croke, Jacky; McKergow, Lucy A.

doi:10.1016/j.geomorph.2008.09.003

Cited by 130 publications

(80 citation statements)

References 43 publications

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“…We acknowledge the assumptions and limitations within both the long-term and contemporary data sets, and that these data need to be interpreted carefully. These assumptions include: that the long-term erosion rate is equivalent to the denudation rate, the relatively short time frame of contemporary data (Bainbridge et al, 2014), the variability of sediment yield estimates between wet and dry years , the representativeness of sediment storage and channel avulsion particularly for the low gradient western catchments (Croke et al, 2015;Fielding et al, 2006), and the potentially poor representation of soil erosion from Tertiary basalts (Pillans, 1997) that are known to contribute significant amounts of fine sediment and phosphorus (P) to the outer GBR (Douglas et al, 2008;Hughes et al, 2009;McCulloch et al, 2003b).…”

Section: Discussionmentioning

confidence: 99%

Combining contemporary and long-term erosion rates to target erosion hot-spots in the Great Barrier Reef, Australia

et al. 2015

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Highlights This paper presents the first non-modelled estimates of contemporary measured erosion rates against background long term erosion rates in the Great Barrier Reef (GBR) catchments. Using an accelerated erosion factor (AEF), this study has highlighted that there are very specific 'hot-spot' areas that warrant priority treatment in terms of catchment remediation (Bowen sub-catchment, Upper Burdekin sub-catchment and low cover grazing areas). Due to the large intra-catchment variability of erosion in space and time, this study highlights that having a single end of catchment water quality target is inappropriate. Sub-catchment monitoring and evaluation is more suitable. The erosion rates presented in this paper represent a more robust way to 'bench-mark' current erosion rates compared with the current water quality 'targets'. AbstractMethods for prioritising catchment remediation are based on understanding the source of sediment over the short-medium timescales (10-10 2 years) using techniques such as sediment finger-printing, sediment flux monitoring, and catchment modelling. Because such approaches do not necessarily quantify the natural variation in sediment flux over the longer timescale, they often represent background or pre-agricultural erosion rates poorly. This study compares long-term (~100 to >10,000 years) erosion rates derived from terrestrial cosmogenic nuclides ( 10 Be) with contemporary erosion rates obtained by monitoring sediment fluxes over ~5-10 years. The ratio of these two data sets provides a measure of the accelerated erosion factor (AEF), which can be used to identify erosion hot-spots at the sub-catchment scale. The study area is the Burdekin catchment, the largest source of contemporary sediment to the Great Barrier Reef lagoon. Long-term erosion rates vary from <0.0077 mm yr -1 in the Suttor and Belyando subcatchments to 0.0296 mm yr -1 in the Bowen. The contemporary erosion rates are highest on small hillslopes with patchy ground cover (0.2726 mm yr -1 ) and in the Bowen sub-catchment (0.2207 mm yr -1 ), and lowest in the Belyando sub-catchment (0.0019 mm yr -1 ). All but two of the sub-catchment sites have an AEF > 1.0, indicating higher contemporary erosion rates than estimated long-term averages. Results confirm that the contemporary or agriculturally-induced erosion rates at these sites have increased considerably. Within the context of the Reef Water Quality Protection Plan, these results provide justification for water quality targets to be set at the sub-catchment scale, particularly for large and geomorphically diverse catchments.

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Section: Discussionmentioning

confidence: 99%

Combining contemporary and long-term erosion rates to target erosion hot-spots in the Great Barrier Reef, Australia

et al. 2015

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“…Amongst present needs for improved models and the estimation of associated uncertainties, what stands out is the impact of sampling of sediment sources and of sediment in suspension, and the development of models which evaluate uncertainties (Motha et al, 2003;Hughes et al, 2009;Collins et al, 2012;Clarke, 2014). Sampling strategies of sediment sources and of suspended sediment are crucial if data are to reflect adequately all the dynamics which the modeller intends to include when describing processes within the watershed under study.…”

Section: The Contextmentioning

confidence: 99%

Evaluating sampling efficiency when estimating sediment source contributions to suspended sediment in rivers by fingerprinting

Clarke

Minella

2016

Hydrological Processes

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Abstract:A general method is proposed which measures the increase in uncertainty when sampling effort is reduced in sediment fingerprinting. The method gives quantitative measures of how reduced sampling of material in one of the source areas, and/or of suspended sediment in streams, increases the uncertainties in the proportions of sediment contributed from the sources. Because the proportions of sediment contributed by the source areas must add to one, standard errors of the estimated proportions cannot be used as the usual measures of uncertainty: the paper uses instead the volume of the joint 95% confidence region for the estimated proportions. The paper shows how the uncertainty in this volume changes as numbers of suspended sediment samples, and the numbers of samples collected from cropped fields, are reduced by successive steps from 24 (20, in the case of cropped fields) to 16, 12, 8, 4 and 2 samples. As expected, uncertainty increases rapidly as the number of samples -whether of suspended sediment or from cropped fields -is reduced drastically. The pattern of increasing uncertainty is similar both for reductions in suspended sediment sampling, and for reduced sampling from cropped areas. When the number of suspended sediment samples, and the number of samples from cropped fields, are reduced to the same values, the increase in uncertainty from fewer suspended sediment samples was always slightly greater than the increased uncertainty from the reduced sampling of cropped areas, although this finding took no account of differences in the costs of field sampling and laboratory analysis.

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“…The geochemical characteristics of eroded sediments are strongly influenced by those of the rock types from which they are derived (Klages and Hsieh 1975;Caitcheon et al 2006) as eroded sediments often maintain their parent rock geochemistry (Hughes et al 2009). By sampling river sediment and comparing the geochemistry of sediment samples with those collected from potential source areas, the relative contribution of different sources to the sediment discharge can be determined.…”

Section: Introductionmentioning

confidence: 99%

Quantifying sources of suspended sediment in three size fractions

2015

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Purpose Identifying of the sources, stores and pathways of sediments in a catchment is essential to accurately target management actions designed to reduce sediment delivery to receiving waters. Fingerprinting the source of sediment using geochemical properties has increasingly been accepted as an accurate approach for quantifying the contribution of different sources to river sediment discharge. In this study, we seek to examine the effect of particle size and location of the sources on their contribution to suspended sediments. Materials and methods Geochemical tracers (n=41) were employed to calculate proportional contributions of sediment to Emu Creek, a predominantly pastoral catchment (911 km 2 ) in south-eastern Queensland, Australia. The study focused on two high flow events (10-and 6-year return periods) and some lower flow events which occurred during the 18 months from October 2011 to March 2013. Source contributions were determined at eight spatially distributed sites in major tributaries and along the main channel of Emu Creek. Source determination at the in-stream sites was done using end member samples (based on the underlying rock type) collected upstream of the site of interest, thus indicating how different sources dominate at different locations downstream. To examine whether different size fractions shared similar provenances, three size fractions of both source and suspended samples including fine silt and clay (<10 μm), silt (10-63 μm) and fine sand (63-212 μm) were analysed. Results and discussionThe source apportionment results using the distribution mixing model indicate that particle size and location of sources within a catchment are major factors that affect the measured contribution of sources to suspended sediments. The closer a suspended sediment sampling site is to a potential source, the more likely it is that source of sediment will dominate the material being sampled. Conclusions For all size fractions, proximal sources of sediment make a higher contribution to suspended sediments than distal sources. This indicates that management actions should be focused on the more proximal sources to the point of interest/impact. Although proximal soil sources were major contributor of sediments in all three size fractions, the percentage of contribution greatly vary in different size fractions, emphasising the need to trace the size fraction which is causing the downstream problems.

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Sediment source changes over the last 250 years in a dry-tropical catchment, central Queensland, Australia

Cited by 130 publications

References 43 publications

Combining contemporary and long-term erosion rates to target erosion hot-spots in the Great Barrier Reef, Australia

Combining contemporary and long-term erosion rates to target erosion hot-spots in the Great Barrier Reef, Australia

Evaluating sampling efficiency when estimating sediment source contributions to suspended sediment in rivers by fingerprinting

Quantifying sources of suspended sediment in three size fractions

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