Sources of fine sediment recovered from the channel bed of lowland groundwater-fed catchments in the UK

Groundwater-fed, lowland permeable catchments in the UK are particularly susceptible to fine sediment accumulation on the bed of their main channel systems. Appropriate catchment management solutions are therefore required. Accurate targeting of sediment abatement strategies is, however, hampered by the dearth of reliable information on the principal sediment sources involved. In view of this, a composite fingerprinting technique, incorporating uncertainty analysis, has been used to investigate the primary sources of fine sediment samples recovered from a total of 18 individual sampling sites on the channel bed of the rivers Frome (∼ 437 km2) and Piddle (∼ 183 km2), Dorset, UK. In the Frome study catchment, mean relative contributions from areas of woodland, pasture and cultivation, and from channel banks/subsurface sources ranged between 1 ± 1%–6 ± 2%, 10 ± 2%–42 ± 2%, 44 ± 4%–81 ± 2% and 7 ± 2%–19 ± 4%, respectively. The corresponding mean relative contributions in the Piddle study area were 1 ± 1%–11 ± 4% (woodland), 10 ± 2%–28 ± 4% (pasture), 44 ± 2%–80 ± 2% (cultivated) and 7 ± 2%–21 ± 2% (channel banks and subsurface sources). These findings have important implications for establishing a scientific basis for assisting the targeting of sediment management and control policies.