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

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dc.contributor.authorSmith, HGen_AU
dc.contributor.authorSheridan, GJen_AU
dc.contributor.authorNyman, Pen_AU
dc.contributor.authorChild, DPen_AU
dc.contributor.authorLane, PNJen_AU
dc.contributor.authorHotchkis, MACen_AU
dc.contributor.authorJacobsen, GEen_AU
dc.date.accessioned2012-04-19T04:08:57Zen_AU
dc.date.available2012-04-19T04:08:57Zen_AU
dc.date.issued2012-02-15en_AU
dc.date.statistics2012-04-19en_AU
dc.description.abstractFine sediment supply has been identified as an important factor contributing to the initiation of runoff-generated debris flows after fire. However, despite the significance of fines for post-fire debris flow generation, no investigations have sought to quantify sources of this material in debris flow affected catchments. In this study, we employ fallout radionuclides ((CS)-C-137, Pb-210(ex) and Pu-239,Pu-240) as tracers to measure proportional contributions of fine sediment (<10 mu m) from hillslope surface and channel bank sources to levee and terminal fan deposits formed by post-fire debris flows in two forest catchments in southeastern Australia. While Cs-137 and Pb-210(ex) have been widely used in sediment tracing studies, application of Pu as a tracer represents a recent development and was limited to only one catchment. The ranges in estimated proportional hillslope surface contributions of fine sediment to individual debris flow deposits in each catchment were 22-69% and 32-74%. The greater susceptibility of Pb-210(ex) to apparent reductions in the ash content of channel deposits relative to hillslope sources resulted in its exclusion from the final analysis. No systematic change in the proportional source contributions to debris flow deposits was observed with distance downstream from channel initiation points. Instead, spatial variability in source contributions was largely influenced by the pattern of debris flow surges forming the deposits. Linking the tracing analysis with interpretation of depositional evidence allowed reconstruction of temporal sequences in sediment source contributions to debris flow surges. Hillslope source inputs dominated most elevated channel deposits such as marginal levees that were formed under peak flow conditions. This indicated the importance of hillslope runoff and fine sediment supply for debris flow generation in both catchments. In contrast, material stored within channels that was deposited during subsequent surges was predominantly channel-derived. The results demonstrate that fallout radionuclide tracers may provide unique information on changing source contributions of fine sediment during debris flow events. (C) 2011 Elsevier B.V. All rights reserved.en_AU
dc.identifier.citationSmith, H. G., Sheridan, G. J., Nyman, P., Child, D. P., Lane, P.N.J., Hotchkis, M. A. C., & Jacobsen, G. E. (2012). Quantifying sources of fine sediment supplied to post-fire debris flows using fallout radionuclide tracers. Geomorphology, 139, 403-415. doi:10.1016/j.geomorph.2011.11.005en_AU
dc.identifier.govdoc4202en_AU
dc.identifier.issn0169-555Xen_AU
dc.identifier.journaltitleGeomorphologyen_AU
dc.identifier.pagination403-415en_AU
dc.identifier.urihttp://dx.doi.org/10.1016/j.geomorph.2011.11.005en_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/4175en_AU
dc.identifier.volume139en_AU
dc.language.isoenen_AU
dc.publisherElsevieren_AU
dc.subjectSedimentsen_AU
dc.subjectPlutoniumen_AU
dc.subjectRadioisotopesen_AU
dc.subjectFiresen_AU
dc.subjectTracer techniquesen_AU
dc.subjectRunoffen_AU
dc.titleQuantifying sources of fine sediment supplied to post-fire debris flows in forest catchments using fallout radionuclide tracersen_AU
dc.typeJournal Articleen_AU
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