Datensatz

Zusammenfassung

To achieve resilient farming systems, it is necessary to establish the impacts that agricultural intensification has had on soil erosion, catchment sediment sources and yields so that the ‘gap’ requiring management is understood. Within the UK, many field-based measurements of soil erosion have been published. However, attempts to incorporate these measurements into a coherent conceptual model of changing sediment dynamics in temperate agricultural catchments are limited. The little data available suggests that landscape-scale soil erosion rates are likely to be comparable to typical modern river sediment yields. This finding cannot be easily reconciled with some observed post-1950s increases in lake sediment yields, the common finding that topsoil erosion typically dominates sediment contributions, and that low sediment delivery ratios are common. Measured channel bank erosion rates can, however, be high on a landscape scale and possibly account for this discrepancy. A simple colour-based sediment source tracing method is used in 14 catchments and shows that channel bank erosion dominates sediment sources more often that currently accepted knowledge would suggest is likely. Sediment sources did not change significantly when comparing periods of low flow to extreme high flow events in many catchments. It is concluded that the resilience of agricultural catchments to environmental changes is likely to be highly spatially variable within temperate landscapes. Low connectivity and a dominant channel bank source suggest high resilience in some catchments, whilst in others, high erodibility soils that are well connected to river channels can result in a system being very reactive to environmental shocks.