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Sediment dynamics of the Severn Estuary and inner Bristol Channel
McLaren, P.; Collins, M.B.; Gao, S.; Powys, R.I.L. (1993). Sediment dynamics of the Severn Estuary and inner Bristol Channel. J. Geol. Soc. Lond. 150(3): 589-603
In: Journal of the Geological Society of London: London. ISSN 0016-7649, more
Peer reviewed article

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Keywords
    Estuaries; Grain size; Mud flats; Sediment transport; Wetlands; ANE, British Isles, Bristol Channel [Marine Regions]; ANE, British Isles, Severn Estuary [Marine Regions]; Marine

Authors  Top 
  • McLaren, P.
  • Collins, M.B.
  • Gao, S.
  • Powys, R.I.L.

Abstract
    Net sediment transport pathways have been determined in many environments by studying grain size trends. This approach is extended here to an inner shelf environment, with improved statistical techniques. Patterns of net surficial sediment transport are proposed, indicating that the area is dominated by up-estuary transport. Exceptions exist in the form of radial mud transport at the river mouths and (clockwise) sand circulation around linear sandbanks. Six different sedimentary environments are defined on the basis of the shape of the 'transfer function' and its relationship to the grain size distributions. Erosion takes place along the axis of the estuary. Dynamic equilibrium is reached around the linear sandbanks, whilst accretion occurs at the head of the estuary and where there are riverine inputs. The results are compared with numerical model outputs, representing water movement and sediment transport. Over the seaward part of the study area, there is agreement between the two approaches; contradictions increase, however, towards the upper reaches of the estuary. The discrepancies can be attributed to: (1) inherent differences between patterns of water and sediment movement; (2) difficulties in modelling intertidal boundary conditions; (3) inadequate representation of river influences in the models; and (4) time-scale differences, associated with sediment transport processes.

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