SEDIMENT YIELD DETERMINATION USING URANIUM-SERIES RADIONUCLIDES - THECASE OF THE WASH AND FENLAND DRAINAGE-BASIN, EASTERN ENGLAND

Water and sediment samples were collected from the Fenland drainage ba sin to assess the fluvial contribution to the sedimentbudget of The Wa sh, on the east coast of England. Using the uranium-series disequilibr ium found in the products of the weathering system (river sediment and water), the ratio of material carried in solid form to that dissolved (U-s/U-w) was assessed and the total flux of weathered material (sedi ment yield) was quantified, The results show that the U,IU, ratio is c ontrolled to a degree by catchment geology and hydrology, and that the re is a marginal seasonal increase from between 3.28 +/- 3.95 and 4.60 +/- 0.44 (summer mean and weighted mean) to between 5.35 +/- 3.05 and 6.07 +/- 0.63 (winter mean and weighted mean). The best estimate of a nnual sediment flux from the Fenland to The Wash is between 2800 and 1 7,700 tonnes yr(-1), equivalent to a rate of 0.22-1.42 tonnes km(-2) y r(-1). This is lower than previous estimates for the region, but reinf orces the argument that sediment reworking within The Wash and erosion of the adjacent coasts and sea beds are important sources of sediment for the intertidal flats and salt marshes.