This thesis deals with the study of flow through tailings dams. Examination of the current practices led to the construction of a valid experimental model. A unique system of instrumentation was developed, which was employed successfully to measure pore water pressures accurately and thus provide the necessary information to locate the position of the phreatic surface. Using the developed technique, models of tailings dams were constructed and monitored and it was discovered that a major deviation in the expected position of the phreatic surface occurred in a tailings dam. Further investigation by the construction of various types of dams led to the redefining of the phreatic surface and thus the flow regime. A computer programme based on the use of the finite difference technique was applied to water retention dams and found to locate the position of the phreatic surface accurately.