Susceptibility to rill erosion of a 12-year-old soil reconstructed after coal mining

For coal extraction, soil must be excavated and removed from the surface, with possible negative environmental impacts, for example, soil disruption and increased erosion. Soils constructed after coal mining may be affected by an intense process of rill erosion. The purpose of this study was to estimate the soil detachment rate resulting from the flow concentrated in rills and determine the critical shear stress and rill erodibility factor in the laboratory. The tests were performed with samples from the 0-0.20 m layer of a soil constructed 12 years earlier in a coal mining area in Candiota, in the south of Brazil. In this experiment, an increase of soil detachment rates in rills was observed when the surface flow increased up to a rate of 17.5 L min −1 , due to higher flow shear stress. The rill erodibility factor (0.0044 kg N −1 s −1 ) was derived from the adjusted linear relationship between the flow shear stress and rill detachment rate. The critical shear stress of the soil was 0.432 Pa. Any flow shear stress in the rill exceeding this value causes soil detachment in the rills.