A one-dimensional numerical model, ROCKFLOW, has been developed to analyze unsteady non-linear flow through coarse porous media. The model is particularly applicable to flow through valley fills and rock drains resulting from mining operations and takes factors such as the spatial variability of material properties and the variability of the cross-sectional geometry into account. The modified Saint-Venant equations together with the Forchheimer equation constitute the mathematical formulation of the flow system. The model employs a four-point finite difference method and a Newton-Raphson scheme to solve the resulting non-linear equations.With regard to the vertical heterogeneity of the materials, a superposition method has been developed and used in the model to account for changes in material properties. Laboratory studies on three, 1.5m long, rockfills made of different homogeneous materials and also a layered rockfill were used to verify the model under different initial and boundary conditions. First, the material hydraulic parameters were determined using steady-state conditions in the physical models. The resulting hydraulic parameters were then used to model unsteady conditions. It was found that the model is able to reproduce the experimental results well in terms of both water surface profiles and depth variation with time curves in the physical models. There is a need to minimize the environmental impacts of mining activities. ROCKFLOW can be applied to valley fills under field conditions to test various design scenarios and to thereby assess their potential impact on the environment (e.g. modified flow regime in the downstream channel).

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