Laboratory rainfall simulator studies of selected open-cut coal mine overburden spoils from Central Queensland

Data on the erodibility of overburden spoils resulting from open-cut coal mining are limited. These data are required to derive parameters for erosion prediction models which can be used in the design of re-formed landscapes after mining. In this study, laboratory rainfall simulation data were used to derive CREAMS (Chemicals, Runoff and Erosion from Agricultural Management Systems) interrill erodibility parameters K and n(bov) for Central Queensland coal mine overburden spoils. For the spoils studied, K values ranged from 0.0111 to 0.1398 Mg . ha . h/(ha . MJ . mm) and n(bov) values ranged from 0.0004 to 0.0081. Sediment yield was transport controlled. Results for 1 spoil, South Blackwater Terang, showed that total soil loss increased linearly with slope, and both K and n(bov) varied non-linearly with slope. If a constant set of K and n(bov) values is used in modelling, CREAMS over-predicts spoil loss for slopes greater than that for which the parameter values were determined, and under-predicts spoil loss for slopes less than that for which the parameter values were determined. The results show evidence of differences between mine spoils and agricultural soils, including modality of size distribution of surface sediment available for erosion, a higher percentage of dispersed clays in eroded sediment from mine spoils than from agricultural soils, and the observed amount of surface sealing and crust formation. These differences indicate that erosion-erodibility parameters for mine spoils should be measured and that agricultural soil parameters should not be a basis for estimates of mine spoil parameters.