Restoring earth surface processes through landform design. A 13-year monitoring of a geomorphic reclamation model for quarries on slopes

摘要

The application of geomorphic principles to land reclamation after surface mining has been reported in the literature since the mid-1990s, mostly from Australia, Canada and the USA. This paper discusses the reclamation problems of contour mining and quarries on slopes, where steep gradients are prone to both mass movement and water erosion. To address these problems simultaneously, a geomorphic model for reclaiming surface mined slopes is described. Called the ‘highwall-trench-concave slope’ model, it was fi rst applied in the 1995 reclamation of a quarry on a slope (La Revilla) in Central Spain.The geomorphic model does not reproduce the original topography, but has two very different sectors and objectives: (i) the highwall–trench sector allows the former quarry face to evolve naturally by erosion, accommodating fallen debris by means of a trench constructed at the toe of the highwall; (ii) the concave-slope base sector, mimicking the landforms of the surrounding undisturbed landscape, promotes soil formation and the establishment of self-sustaining, functional ecosystems in the area protected from sedimentation by the trench. The model improves upon simple topographic reconstruction, because it rebuilds the surfi cial geology architecture and facilitates re-establishment of equilibrium slopes through the management and control of geomorphic processes.Thirteen years of monitoring of the geomorphic and edaphic evolution of La Revilla reclaimed quarry confi rms that the area is functioning as intended: the highwall is backwasting and material is accumulating at the trench, permitting the recovery of soils and vegetation on the concave slope. However, the trench is fi lling faster than planned, which may lead to run-off and sedimentation on the concave slope once the trench is full. The lesson learned for other scenarios is that the model works well in a twodimensional scheme, but requires a three-dimensional drainage management, breaking the reclaimed area into several watersheds with stream channels.