The use of caesium-137 measurements to establish a sediment budget for the Start catchment, Devon, UK

Abstract

Caesium-137 (137Cs) measurements have been used to investigate the delivery of sediment from the hillslopes to a lake which marks the downstream limit of the small agricultural Start basin in Devon, UK. Total 137Cs inventories and 137Cs depth distributions in sediment cores were used to estimate that the eroded sediment stored within the fields and on the flood plain of the main river was equivalent to sediment yields of ca. 21 and 30 t km-2 year-1, respectively. Based on published information on sediment accumulation in the lake, the minerogenic sediment yield from the basin was estimated to be ca. 29 t km-2 year-1. The erosion rate on the hillslopes in the basin, calculated as the sum of the sediment yield to the lake and the two storage components, is ca. 80 t km-2 year-1. Of the soil eroded from the slopes more than 60% is stored at intermediate locations and the sediment delivery to the lake is less than 40%. The calculated soil erosion rate for the Start basin is consistent with an estimate of the erosion rate for the basin of the nearby Old Mill Reservoir of ca. 63 t km-2 year-1.