Suspended sediment sources in two small lowland agricultural catchments inthe UK

In recent years there has been increasing recognition of the need to includ e sediment control strategies within catchment management plans. Informatio n on the source of the sediment transported by a river is an important requ irement for designing effective sediment control strategies. This paper use s the source fingerprinting approach to establish suspended sediment source s within two small (<4 km(2)) lowland agricultural catchments in the UK, wh ich are both extensively under drained. Representative samples of suspended sediment were collected from both catchments to encompass the expected int er- and intra-storm variability in sediment source. Statistically verified composite fingerprints and multivariate mixing models. incorporating partic le size correction factors, were used to estimate the relative contribution of the potential sediment sources. These included surface sources (classif ied by land use, geology and soil type), eroding channel banks and field dr ains (subsurface sources), Field drains were shown to be important suspende d sediment sources in both catchments, accounting for 27-55% of the sedimen t yields. Bank erosion contributes ca. 10% or less of the sediment yields. Surface sources were found to be important in both catchments contributing between 34-65% of the sediment yield. The above estimates of the relative c ontribution of the individual sediment sources within the study catchments to the overall sediment yield were shown to conceal significant inter- and intra-storm variability in the source contributions. (C) 2001 Elsevier Scie nce B.V. All rights reserved.