EstProc - The development of new algorithms to parametise the mass settling of flocculated estuarine sediments (TR 145)

Manning, A.J. (2004) EstProc - The development of new algorithms to parametise the mass settling of flocculated estuarine sediments (TR 145). Technical Report. HR Wallingford, Wallingford.

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Abstract

Produced within Defra Project FD1905 (EstProc). The effective management of estuarine locations requires accurate models of fine sediment dynamics. For predicting the transport and fate of sediment movement in these situations, the determination of the various spatial and temporal mass fluxes is essential. One particular area which has caused numerous problems, is the modelling and mathematical description of the vertical mass settling flux of fine cohesive sediment, which becomes the depositional flux close to slack water. This flux is the product of the suspended particulate matter (SPM) concentration and the settling velocity. For non-cohesive sediment this is a relatively simple process as the settling velocity is proportional to the particle size. Whereas estuarine muds, which are composed of combinations of clay minerals and different types of biological matter, have the potential to flocculate in to larger aggregates called flocs. The generality in application of existing floc parameterisation techniques specifically for mass settling flux determination, is a point of extreme debate and conjecture. It is therefore the aim of this study to describe a new flocculation model, developed as part of the UK Defra and EA funded EstProc research project (HR Wallingford, 2002), which was based entirely on experimental observations made using low intrusive data acquisition techniques, from a wide range of estuarine water column conditions. The empirical model will be used to reveal the principle inter-relationships controlling natural mud flocculation, and how this consequently effects the resultant depositional fluxes. The empirical model will then be assessed and compared against other approaches which are often incorporated in numerical sediment transport simulation models to parameterise the vertical mass flux.

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