Comparison of Deterministic and Stochastic Criteria for the Initiation of Sediment Motion in Tidal Basins

Current study is refinement and application of a two-dimensional horizontal numerical model to
predict geo-morphological changes in tidal basins. An ADI finite difference algorithm has been used
for solving the governing equations, which consist of the conservation of mass and momentum for the
hydrodynamics, the transport equation for suspended sediment fluxes and the sediment mass
conservation equation for bed level changes. The model includes three criteria for the initiation of
motion (i.e. Shields (1936), Kolahdoozan (1999) and Zanke (2003)). Since the flow is turbulent, its
components have a random nature and sediment transport processes can be expressed by stochastic
approaches. In this study both deterministic and stochastic methods were included in bed load
computations. Verification of model results have been carried out by an experimental study cited in
the literature. Comparisons of results for different criteria for the initiation of motion shows that the
unsteadiness parameters of current have a major effect on the bed level changes in comparison with
turbulence structure of the flow.