Stochastic Models of Suspended-Sediment Dispersion

Existing probabilistic methods for predicting turbulent dispersion of suspended sediments are reviewed, starting with the early theory of particle diffusion by continuous movements, and proceeding to more recent random walk simulations. The evolutions of these models are explored along with their limiting assumptions. The methods are basically equivalent. The random walk procedure is not restricted in principle to stationary flows, but it imposes probability distribution restrictions that are not present in the continuous movements technique. A basic problem common to both techniques is that detailed information is needed about the turbulent features of the carrying flow. The sediment diffusivity can be obtained from either Lagrangian or Eulerian information provided that the particle properties and turbulent velocity scales satisfy certain specific relationships.