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 c oal mining are limited. These data are required to derive parameters f or erosion prediction models which can be used in the design of re-for med landscapes after mining. In this study, laboratory rainfall simula tion data were used to derive CREAMS (Chemicals, Runoff and Erosion fr om Agricultural Management Systems) interrill erodibility parameters K and n(bov) for Central Queensland coal mine overburden spoils. For th e spoils studied, K values ranged from 0.0111 to 0.1398 Mg . ha . h/(h a . 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 o f 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 f or which the parameter values were determined. The results show eviden ce of differences between mine spoils and agricultural soils, includin g modality of size distribution of surface sediment available for eros ion, a higher percentage of dispersed clays in eroded sediment from mi ne spoils than from agricultural soils, and the observed amount of sur face sealing and crust formation. These differences indicate that eros ion-erodibility parameters for mine spoils should be measured and that agricultural soil parameters should not be a basis for estimates of m ine spoil parameters.