Results of an experimental program concerning the movement of particulates in a porous medium under conditions of non-linear flow are presented. The results are compared with the limited existing data and a model developed by Sakthivadivel [8] for linear flow conditions. Modifications were required to this model to allow it to be used under the present conditions. Examination of the results suggested an alternative transport model using suitable dimensionless parameters. This model is shown to be superior to the existing model.