Establishing fine-grained sediment budgets for the Pang and Lambourn LOCAR catchments, UK

An integrated approach to data collection combining the use of Cs-137 measurements, sediment source fingerprinting, bed sediment surveys and conventional river monitoring, has been successfully employed to establish the fine-grained sediment budgets of two Lowland groundwater-fed catchments in the UK. Gross surface erosion is higher on cultivated land (Pang: 55263 t yr(-1) or 507 t km(-2) yr(-1); Lambourn: 79997 t yr(-1) or 437 t km(-2) yr(-1)) than on pasture (Pang: 1960 t yr(-1) or 140 t km(-2) yr(-1); Lambourn: 1425 t yr(-1) or 95 t km(-2) yr(-1)) in both study areas and a substantial proportion of the mobilized sediment is sequestered within the fields (Pang: 28 058 t yr(-1) or 228 t km(-2) yr(-1); Lambourn: 55 575 t yr(-1) or 281 t km(-2) yr(-1)) and between the individual fields and the river channel network (Pang: 28 672 t yr(-1) or 233 t km(-2) yr(-1); Lambourn: 24782 t yr(-1) or 125 t km(-2) yr(-1)). The sediment contribution from banks and subsurface sources is relatively low and typically ca. 5 t yr(-1) in the Pang and ca. 11 t yr(-1) in the Lambourn, representing only about 1% of the suspended sediment output from each study catchment. The mean level of fine-grained sediment storage in the main channel system is equivalent to 38% (Pang) and 21% (Lambourn) of the respective mean annual suspended sediment yields of the two catchments. The estimated sediment delivery ratio for both study catchments is ca. 1%. (c) 2006 Elsevier B.V. All rights reserved.