Investigating the remobilization of fine sediment stored on the channel bed of lowland permeable catchments in the UK.

The bed of the main channel system represents an important store of fine sediment in lowland groundwater-fed catchments, in the UK, on account of the deposition promoted by their naturally subdued hydrological regimes, low channel gradients and the reduction of flows caused by water abstraction. Although a number of recent investigations have contributed to an improved understanding of the magnitude and spatio-temporal variability of fine sediment storage, much less is known about the role of remobilization of fine sediment from the channel bed in the suspended sediment fluxes from lowland permeable catchments. To address this shortcoming, the authors report the use of a composite fingerprinting technique, incorporating uncertainty analysis, to investigate the magnitude and timing of the remobilization of fine sediment sequestered on the channel bed of three lowland permeable catchments in the UK. The findings are used to assess the relative contributions of three principal potential sediment sources to the sediment loads sampled at the catchment outlets, namely: fine sediment remobilized from the channel bed of the main stem; suspended sediment inputs from tributary sub-catchments; and sediment originating from channel banks along the main channel.