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HR Wallingford, Howbery Park, Wallingford, Oxon OX10 8BA, UK (email: rls{at}hrwallingford.co.uk)
A new model is described that simulates the paths taken by a large number of identified (‘tagged’) sand grains in coastal areas in response to waves and currents. A number of practical applications require such a Lagrangian approach, as distinct from the more traditional Eulerian calculations of the transport rates of bulk quantities of identical, non-tagged, grains. Such applications might include studies on the dispersal of dredged spoil, or on the release of contaminated particulate material.
The particle-tracking algorithm determining the movement of tagged grains takes account of the following processes:
A novel method of simulating these processes has been devised, by formulating functions to parameterize each of them, and then specifying a grain speed as the product of the functions. The particle-tracking algorithm is implemented within HR Wallingford's SEDPLUME-RW model, originally devised to track the dispersal of muddy sediments. This in turn is driven by currents and waves computed by the hydrodynamic model TELEMAC. A validation exercise simulating dispersal of radioactive sand tracer measured in the 1960s in Morecambe Bay is described.
