title: Use of sediment source fingerprinting to assess the role of subsurface erosion in the supply of fine sediment in a degraded catchment in the Eastern Cape, South Africa.
abstract: Sediment source fingerprinting has been successfully deployed to provide information on the surface and subsurface sources of sediment in many catchments around the world. However, there is still scope to re-examine some of the major assumptions of the technique with reference to the number of fingerprint properties used in the model, the number of model iterations and the potential uncertainties of using more than one sediment core collected from the same floodplain sink. We investigated the role of subsurface erosion in the supply of fine sediment to two sediment cores collected from a floodplain in a small degraded catchment in the Eastern Cape, South Africa. The results showed that increasing the number of individual fingerprint properties in the composite signature did not improve the model goodness-of-fit. This is still a much debated issue in sediment source fingerprinting. To test the goodness-of-fit further, the number of model repeat iterations was increased from 5000 to 30,000. However, this did not reduce uncertainty ranges in modelled source proportions nor improve the model goodness-of-fit. The estimated sediment source contributions were not consistent with the available published data on erosion processes in the study catchment. The temporal pattern of sediment source contributions predicted for the two sediment cores was very different despite the cores being collected in close proximity from the same floodplain. This highlights some of the potential limitations associated with using floodplain cores to reconstruct catchment erosion processes and associated sediment source contributions. For the source tracing approach in general, the findings here suggest the need for further investigations into uncertainties related to the number of fingerprint properties included in un-mixing models. The findings support the current widespread use of ≤5000 model repeat iterations for estimating the key sources of sediment samples.
authors: Department of Geography and Environmental Sciences, North-West University, Mafikeng Campus, Private Bag X2046, Mmabatho 2735, South Africa. Electronic address: Munyaradzi.Manjoro@nwu.ac.za.
authors: Munyaradzi
authors: M
authors: Manjoro
authors: Department of Geography, Rhodes University, Drosty Rd, Grahamstown, 6139, South Africa. Electronic address: K.Rowntree@ru.ac.za.
authors: Kate
authors: K
authors: Rowntree
authors: Geosciences Department, Nelson Mandela Metropolitan University, Port Elizabeth, 6031, South Africa. Electronic address: Vincent.Kakembo@nmmu.ac.za.
authors: Vincent
authors: V
authors: Kakembo
authors: Department of Geography, Rhodes University, Drosty Rd, Grahamstown, 6139, South Africa; Department of Environmental and Geographical Sciences, University of Northampton, Northampton, NN2 6JD, UK. Electronic address: Ian.Foster@northampton.ac.uk.
authors: Ian
authors: I
authors: Foster
authors: Department of Sustainable Soil and Grassland Systems, Rothamstead Research, North Wyke, EX20 2SB, UK. Electronic address: Adrian.Collins@Rothamsted.ac.uk.
authors: Adrian L
authors: AL
authors: Collins
mesh_terms: D004784:Environmental Monitoring; D019015:Geologic Sediments; D008962:Models, Theoretical; D013019:South Africa; D035501:Uncertainty
keywords: Eastern Cape; Sediment source fingerprinting; gully erosion; mass balance modelling; uncertainty analysis