ERODIBILITY AND SEDIMENT YIELD BY NATURAL RAINFALL FROM RECONSTRUCTED MINE SOILS

Abstract

Standard erosion plots, 4.6 m × 22.1 m with a 9% slope, were established at the Alston Surface Mine in Ohio County, Kentucky. Topsoil, subsoil, and mine spoil were reconstructed according to contemporary reclamation techniques using bulldozers and scraper pans. The following parameters were evaluated under natural rainfall conditions: runoff, erodibility, and sediment yield. Mine spoil yielded significantly greater runoff volumes, compared with reconstructed topsoil and subsoil. Average curve numbers (CN) were 89.1, 90.1, and 94.7 for bare topsoil, subsoil, and mine spoil, respectively. The subsoil plot generated the largest amount of sediment and was significantly more erodible than topsoil and mine spoil. The average annual erodibility (K) factor was .046 for topsoil, .067 for subsoil, and .051 for mine spoil, with units of Mg ha h (ha MJ mm)−1. Erodibility of the mine spoil in this study was more than twice that measured from an earlier rainfall simulation study at this same site. Differences in the degree of physical weathering were believed to be the primary contributing factor and, therefore, have important implications when assessing the erodibility of highly weathered spoil materials (e.g., abandoned mine lands). Compared with the soil interpretation record's K factor estimate for the soil series evaluated in this study, the reconstructed topsoil was not inherently more erodible than when existing in its natural, undisturbed condition. Therefore, factors that the mine operator can control (e.g., slope, vegetative cover, management practices) will likely have a greater impact on whether erosion losses from reconstructed soils are significantly greater than losses that occur under pre-mining conditions.