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Source, storage and mobilisation of fine sediment in a chalk stream system
Author(s) -
Walling D. E.,
Amos C. M.
Publication year - 1999
Publication title -
hydrological processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.222
H-Index - 161
eISSN - 1099-1085
pISSN - 0885-6087
DOI - 10.1002/(sici)1099-1085(19990228)13:3<323::aid-hyp741>3.0.co;2-k
Subject(s) - sediment , hydrology (agriculture) , sedimentary budget , channel (broadcasting) , turbidity , geology , environmental science , turbidite , sediment transport , geomorphology , oceanography , geotechnical engineering , engineering , electrical engineering
Concern for sediment problems in the Upper River Piddle, Dorset, including accumulation of fine sediment on the channel bed and elevated turbidity levels during periods of stable flow, provided the stimulus for a detailed field investigation of the sediment dynamics of this chalk stream system undertaken during the period November 1991 to April 1993. Two monitoring stations were established at South Farm, Piddletrenthide and Lawrence Mede, Piddlehinton and estimates of suspended sediment load were obtained for these two sites. In addition, suspended sediment concentrations and bed sediment loadings were regularly sampled at several other sites, sediment traps were deployed at ten representative sites along the river channel, field observations of sediment sources and pathways were made during storm events and a sediment source fingerprinting study was undertaken. Estimates of annual suspended sediment yield provided values of 9–12 t km −2 year −1 , which must be seen as low by UK standards. Elevated suspended sediment concentrations were not restricted to storm events, but occurred throughout the monitoring period in response to remobilisation of sediment stored in the channel. The evidence provided by the sediment loads recorded at the two monitoring stations, by the sediment traps and by the measurements of bed sediment loading, indicated that substantial amounts of sediment accumulated in the channel of the upper and middle reaches of the river during the winter months and that this ‘slug’ of sediment was slowly transmitted downstream during the following summer. Fingerprinting of the transported sediment and of potential sources indicated that the dominant source of suspended sediment was likely to be surface soil from cultivated areas. Field reconnaissance surveys undertaken during storm events indicated that substantial inputs of surface runoff and suspended sediment entered the stream. Much of this sediment is, however, stored within the channel system and slowly transmitted downstream. Copyright © 1999 John Wiley & Sons, Ltd.