Application of Landform Evolution Models to Assess Long-Term Contour Bank Stability in Constructed Post-Mining Landforms

In the mining industry, once valuable minerals are extracted, waste rock dumps are piled at designated sites. These dumps are capped with topsoil, and the hillslopes are seeded with pasture species. The constructed post-mining landscapes are expected to gradually integrate with the surrounding natural terrain. However, due to the physical and chemical properties of the waste material, limited vegetation cover, and hillslope geometries, these landforms are susceptible to rill and gully erosion. Ensuring their long-term erosional stability is therefore a primary challenge. Contour banks are occasionally constructed across rehabilitated slopes to mitigate erosion, yet predicting their long-term effectiveness at each site remains challenging. In this study, we evaluated the stability of contour banks using a physics-based landform evolution model (LEM). A LiDAR-derived digital elevation model (DEM) of a unique hillslope, with one section containing contour banks and another without, served as the study site. The State Space Soil Production and Assessment Model (SSSPAM) was applied over a 100-year simulation period with annual time steps, parameterised for site-specific conditions. The model results indicate that contour banks at this site gradually erode, and that after 100 years, average erosion rates were comparable between slopes with and without contour banks. These findings are consistent with short-term visible observations, showing early signs of contour bank erosion. The study highlights the utility of LEMs for assessing the long-term sustainability of erosion-control measures, such as contour banks, in post-mining landscapes. The insights generated from LEMs provide valuable guidance for mine rehabilitation planning and broader land management applications, including terraced landscapes.