A UAV- and field-based investigation of the land degradation and soil erosion at opencast coal mine dumps after 5 years’ evolution of natural processes

Open-pit coal mining has a large impact on land surface, both at the mining pits themselves and at waste sites. After artificial management is stopped, a reclaimed opencast coal mine dump is affected by wind and water erosion from natural processes, resulting in land degradation and even safety incidents. In this paper, the soil erosion and land degradation after 5 years of such natural processes, at the Xilinhot open pit coal mine dump in Inner Mongolia, were investigated. A multi-source data acquisition method was applied: the vegetation coverage index was extracted from GF-1 satellite imagery, high-precision terrain characteristics and the location and degree of soil erosion were obtained using an Unmanned Aerial Vehicle (UAV), and the physical properties of the topsoil were obtained by field sampling. On this basis, the degree and spatial distribution of erosion cracks were identified, and the causes of soil erosion and land degradation were analyzed using a geographical detector. The results show that: 1) The multi-source data acquisition method can provide effective basic data for the quantitative evaluation of the ecological environment at dumps; 2) slope aspect and vegetation fractional coverage are the main factors affecting the degree of degradation and soil erosion. Based on this analysis, several countermeasures are proposed to mitigate land degradation: 1) The windward slope be designed to imitate the natural landform; 2) engineering measures should be applied at the slope to restrain soil erosion; 3) pioneer plants should be widely planted on the platform at the early stage of reclamation.