A review of sediment dynamics in the Severn Estuary: Influence of flocculation

Manning, A.J. and Langston, W. and Jonas, P.J.C. (2010) A review of sediment dynamics in the Severn Estuary: Influence of flocculation. Marine Pollution Bulletin, 61 (1-3). pp. 37-51.

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Official URL: http://www.sciencedirect.com/science/article/pii/S...


This paper provides a review and critique of the distributions and characteristics of non-cohesive and cohesive sediments within the Severn Estuary, with particular reference to floc properties. The estuary is hyper-tidal and, consequently, highly turbid along most of its length and it generally has two turbidity maxima. In the upper reaches of the estuary, suspended particulate matter (SPM) concentrations can be in excess of 10 g l−1 for river flows up to 50 m3 s−1, rising to over 50 g l−1 during periods of lower river flow. The lower estuary turbidity maximum originates in the vicinity of Bridgwater Bay where SPM concentrations may vary between 0.1–200 g l−1. The formation of fluid mud is coupled to the spring-neap cycle and strong vertical gradients in SPM concentrations produce turbulence damping and drag reduction effects, and hence impair the ability of the flow to transport sediments. Flocculation is an important mechanism for controlling the behaviour of fine sediments and mean settling velocities of flocs vary between 0.8–6 mm s−1. A secondary consequence of flocculation is the formation of mud:sand mixtures in turbid suspensions. Improved understanding of the significance of flocculation processes is crucial as they may exert an influence on the mechanism by which adsorbed contaminants are transported in the system.

Item Type: Article
Subjects: Coasts > Sediment transport and scour
Coasts > General
Divisions: Coastal
Depositing User: Unnamed user with email i.services@hrwallingford.com
Date Deposited: 02 Apr 2020 09:49
Last Modified: 20 May 2020 10:50
URI: http://eprints.hrwallingford.com/id/eprint/758

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