Prediction of erosion from steep mine waste slopes

Abstract

The prediction of soil erosion by the action of water has been based largely on the universal soil loss equation and its variations, derived from data collected from agricultural land in the USA. Open pit mining creates waste rock or spoil dumps at the angle of repose of the material (typically 35° to 40°). Even after regrading these slopes, relatively steep slope angles will remain, typically steeper than 6° to 8°. Topsoiling is generally required to facilitate revegetation, but bare topsoil is particularly prone to erosion. Mine slopes are therefore quite unlike the agricultural slopes on which the predictive tools for erosion by water were based. The paper discusses the prediction of erosion from steep mine waste slopes in the light of some erosion data collected from laboratory flume and field studies for open pit coal and gold mining situations in Queensland, Australia. Alternative interpretations of the data are presented, which result in different trends when the data are extrapolated up to angle of repose slopes. The effectiveness of both coarse‐grained riprap on the surface and revegetation in limiting erosion are highlighted.