Configuration of Mine Closure Landforms — Geomorphic Approach

Authors: Sawatsky, LF; Beersing, A; Ade, F Download Paper

DOI https://doi.org/10.36487/ACG_repo/852_5

Cite As:
Sawatsky, LF, Beersing, A & Ade, F 2008, 'Configuration of Mine Closure Landforms — Geomorphic Approach', in AB Fourie, M Tibbett, I Weiersbye & P Dye (eds), Mine Closure 2008: Proceedings of the Third International Seminar on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 35-45, https://doi.org/10.36487/ACG_repo/852_5



Abstract:
Post-mining landform contouring is becoming an important consideration in mine planning and permitting in parts of North America. Regulators and stakeholders are becoming increasingly concerned about reclaimed landforms that fail to provide an appearance, ecological productivity, drainage effectiveness, perpetuating vegetation, and stability similar to natural, undisturbed landforms. Mine owners are also becoming concerned about the long-term liabilities associated with reclaiming mine-disturbed land that may be subject to accelerating rates of deterioration through weathering (leading to acid and metalliferous drainage), erosion and salt accumulation. Accordingly, techniques for replicating natural landforms and natural drainage systems are being developed to achieve similar composition, contouring, and hydrologic functions as undisturbed landforms. The geomorphic approach offers appropriate guidance to mine planners and engineers. In place of the typical geometric waste dump shapes with flat tops and homogenous benched sides, the geomorphic approach offers micro-topography provided by dendritic drainage courses with decreasing slopes at the base of the landform, mimicking mature natural landforms. A characteristic drainage density is provided to control overland flow path lengths. Landform slopes are selected to provide adequate drainage without causing excessive risks of erosion. Headwater drainage courses in mountain areas are composed of natural rock-lined channels. In non-mountainous areas, ephemeral drainage courses at headwater areas are frequently composed of vegetated waterways. Downstream of such headwater drainage courses, alluvial channels are built to mimic the regime relationships of equivalent natural systems and facilitate the rapid development of mature alluvial processes in constructed channels, by replicating key characteristics of natural systems that may exist nearby. Designers hope to achieve the type of long-term sustainability that is evident in most natural systems. Replicating natural landscape and natural drainage systems requires a sound understanding of rainfall patterns, evapotranspiration, surface cover and hydrology, hydrogeology, erosion, sedimentation, and fluvial geomorphology. Various principles for replicating natural systems have been developed for landform design and drainage on mine-disturbed land. Several examples of the geomorphic approach show how these principles have been applied to landforms in the oil sands region of Alberta and the coal mines in western Canada and Washington State. Preliminary findings of a large applied research study to develop techniques for replicating natural channels in northern Alberta are summarized.

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