Quantifying sources of fine sediment supplied to post-fire debris flows using fallout radionuclide tracers

Smith, Hugh G.; Sheridan, Gary; Nyman, Petter; Child, David; Lane, Patrick; Hotchkis, M.A.C.; Jacobsen, Geraldine

doi:10.1016/j.geomorph.2011.11.005

Cited by 53 publications

(45 citation statements)

References 72 publications

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“…It is therefore possible for the nuclear testing performed in the Montebello Islands and at Emu Field to have influenced regional fallout concentrations and may explain the deviations in 240 Pu/ 239 Pu ratio observed in studies in the region [8,9,16,17]. We also find that there is significant 236 U in the local fallout.…”

Section: Discussionmentioning

confidence: 53%

“…Studies such as these have in the past commonly used 137 Cs as the tracer isotope [2]. Plutonium, with a similar depositional history and fallout origin as 137 Cs, a similar vertical migration rate in most surface soil types and sediments as 137 Cs [3] (though certain soil compositions, climatic conditions and chemical forms of source material can lead to higher migration rates for Pu compared to Cs [4,5]) and with significantly longer half life ( 239 Pu and 240 Pu have half lives of 24100 and 6560 years, respectively, compared to 137 Cs which has only a 30.07 year half life) is increasingly being used in geomorphological studies such as determination of soil or sediment source materials [6][7][8] and sedimentation determination [9]. Since the peak of atmospheric nuclear testing in 1963, nearly two half lives of 137 Cs have now passed and consequently it is increasingly difficult to detect 137 Cs with high precision in sediments and soils, especially where sample sizes are small.…”

Section: Introductionmentioning

confidence: 99%

“…Recently a number of authors [8,9,16,17] have reported 240/239 plutonium isotopic ratios in Australian soils and sediments lower than the average stratospheric fallout, ranging from 0.11 to 0.169. In the present study, for which preliminary results are reported here, we are studying potential regional sources of fallout in Australia.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Plutonium and uranium contamination in soils from former nuclear weapon test sites in Australia

Child

Hotchkis

2013

Nuclear Instruments and Methods in Physics Research Section B:

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Section: Discussionmentioning

confidence: 53%

Section: Introductionmentioning

confidence: 99%

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Plutonium and uranium contamination in soils from former nuclear weapon test sites in Australia

Child

Hotchkis

2013

Nuclear Instruments and Methods in Physics Research Section B:

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“…[] found that weathering‐limited catchments in plutonic granite terrain in northeast Victoria (southeast Australia) were less susceptible to runoff generated debris flows after wildfire than the adjacent sedimentary catchments. Sedimentary catchments were not weathering‐limited, and the soil mantled hillslopes in these systems provided a major source of fine sediment for postwildfire debris flows [ Smith et al ., ]. Cannon et al .…”

Section: Discussionmentioning

confidence: 99%

Sediment availability on burned hillslopes

Nyman

Sheridan

Moody

et al. 2013

J. Geophys. Res. Earth Surf.

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Erodibility describes the inherent resistance of soil to erosion. Hillslope erosion models typically consider erodibility to be constant with depth. This may not be the case after wildfire because erodibility is partly determined by the availability of noncohesive soil and ash at the surface. This study quantifies erodibility of burned soils using methods that explicitly capture variations in soil properties with depth. Flume experiments on intact cores from three sites in western United States showed that erodibility of fire‐affected soil was highest at the soil surface and declined exponentially within the top 20 mm of the soil profile, with root density and soil depth accounting for 62% of the variation. Variation in erodibility with depth resulted in transient sediment flux during erosion experiments on bounded field plots. Material that contributed to transient flux was conceptualized as a layer of noncohesive material of variable depth (dnc). This depth was related to shear strength measurements and sampled spatially to obtain the probability distribution of noncohesive material as a function of depth below the surface. After wildfire in southeast Australia, the initial dnc ranged from 7.5 to 9.1 mm, which equated to 97–117 Mg ha−1 of noncohesive material. The depth decreased exponentially with time since wildfire to 0.4 mm (or < 5 Mg ha−1) after 3 years of recovery. The results are organized into a framework for modeling fire effects on erodibility as a function of the production and depletion of the noncohesive layer overlying a cohesive layer.

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“…Different particle sizes of sediments and potential sources were used in previous sediment fingerprinting studies including <63 μm as the most common size fraction (e.g., Collins et al 2010Collins et al , 2012Devereux et al 2010;Blake et al 2012;Navratil et al 2012;Poulenard et al 2012), <2000 μm (e.g., Minella et al 2004;Fukuyama et al 2010;Evrard et al 2011), <53 μm (e.g., Fox andPapanicolaou 2007), <10 μm (e.g., Caitcheon et al 2012;Smith et al 2012;Olley et al 2013;Wilkinson et al 2013), <250 μm (e.g., Foster et al 2007;Evrard et al 2013). The sources of the different sediment size fractions may vary as a result of different entrainment processes and transport characteristics.…”

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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Quantifying sources of fine sediment supplied to post-fire debris flows using fallout radionuclide tracers

Cited by 53 publications

References 72 publications

Plutonium and uranium contamination in soils from former nuclear weapon test sites in Australia

Plutonium and uranium contamination in soils from former nuclear weapon test sites in Australia

Sediment availability on burned hillslopes

Quantifying sources of suspended sediment in three size fractions

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