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Sedimentation in the inner estuary of the Thames, and its relation to the regional subsidence

1972; Royal Society; Volume: 272; Issue: 1221 Linguagem: Inglês

10.1098/rsta.1972.0037

2054-0272

J. E. Prentice, David Gray,

Marine and environmental studies

The Inner Thames Estuary is defined as that part of the estuary which lies above the point of widening at Southend and the tidal limit at Teddington Weir (figure 1). In respect of sedimentation it may be divided into three zones. From Teddington to below Tower Bridge the river carries mainly land-derived sediment suspension load is low, and deposition on the bed and banks is slight. From Woolwich Reach to Gravesend Reach is a zone of high suspended load and much sedimentation - these are the ‘Mud Reaches’. Below that, down to Sea Reach, sedimentation is dominated by bed-load transport from the sea. The sedimentation pattern of the Mud Reaches is related to the position of the salt-water-freshwater mixing zone, and so is most sensitive to relative changes of sea level. In point of fact the constitution of this mud is widely variable, varying from 80 down to 10 % of clay, while still retaining its fluid and mobile character. This fluidity appears to be due largely to the loose packing of the flocculated clay particles which it contains, although the relatively high organic content of the mud undoubtedly plays a part. It would, however, be wrong to attribute the peculiar problem associated with the accumulation of fluid mud in the Thames to the organic pollution of the river, for similar deposits are shown in many less-polluted estuaries, e.g. the Taw-Torridge, the Gironde, etc.