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Topographic Reconstruction- IntroductionTopographic reconstruction is the first step towards creating a successful reclamation of landforms. It is a critical part since it is the foundation on which new landscape is built. A dynamic equilibrium exists between the geomorphic process and landforms. Due to land disturbances, which are an inevitable consequence of the economic system the dynamic equilibrium is disturbed. As stated in Munshower (1994) the objective of reclamation is to restore this equilibrium. The equilibrium that exists between the landforms is a result of the combination of various factors with the climatic conditions. The factors are
Due to land disturbances, geomorphic process goes out of balance and nature tries to regain a new dynamic equilibrium. Because of this process, geomorphic process rate is accelerated which leads to land degradation problems.
Land reclamation involves various steps like
The various types of landforms that are created during the process of reclamation are
Hillslopes, drainage basins and stream channels.The main objectives of topographic reconstruction are
Figure 1, showing hillslope, stream channel and drainage basin components (Barnhisel et al 2000)
Laws and regulations influence reclamation efforts to a great extent because it is not possible not to comply with the laws.
Material handling influences cost factor. So it is very important to know the requirements such as type of material
• Physical properties of the materials
• Toxicity
• Position of ground water and the materials
Stability can be defined as the “state under which slope is not subject to failure”. Stable platforms provide stability to the slope.
Water management is an important consideration since water might get contaminated when it flows in and out of the mined areas. It varies from place to place due to the different conditions encountered. In humid areas minimizing soil erosion and water quality deterioration are the main factors.Erosion control is one of the primary considerations. Post-mined landforms are steep and offer very little chances of revegetation. Slope stability, reestablishing original drainage basins will reduce erosion.
According to Munshower (1994), good topographic design is a must for lands that are to be used as farmlands. When reconstruction is done, the degraded site should be tied along with the undisturbed terrain. When vegetation takes place it should fade the boundary and the reconstructed landscape should flow smoothly in to the terrain.
Figure 2, reconstructed landscape flowing smoothly in to the terrain (Munshower 1994)Constraints that are placed on topographic reconstruction are (Toy and Black, 2000)
On-site physical limitations
These are influenced by climatic conditions, ground water condition and topography. Climatic conditions affect reconstruction by influencing erosion and runoff. Topography influences cost because if surfaces are not uniform, earth-moving equipments are necessary.Off-site physical limitations:
Both On and Off-site constraints are influenced by more or less the same factors. Topography, groundwater properties influence offsite constraints. Planning process is affected by compliance to boundary conditions of the surrounding lands. Streams and lakes are one of the most important boundary restrictions. Important considerations are
Off-site land-use limitations:
Lands surrounding a disturbed area are one of the major concerns when reclamation is undertaken because there is every chance that the planned activity for reclamation might affect the lands. Residential areas and highways impose constraints on reconstruction.The most important objective of reconstruction is re-establishing dynamic equilibrium in such a way that it slows down the geomorphic processes and prevents unnatural degradation of landforms. Another important objective of reconstruction should be to restore the landforms as it was before. This is not practically feasible but attempts should be made to mimic post-landforms to pre-landforms to an extent. During planning phase of mining operation, post-disturbance landforms can be mapped. It can be done by conforming to predefined slope and exposure parameters, which can duplicate the pre-disturbance landforms.
Topographic design and construction are greatly influenced by the post-reclamation land-use. Ponds are an important feature in topographic reconstruction. They help in
As stated in Toy and Black,(2000) a common mistake in topographic reconstruction is the assumption of a static system. Lands reclaimed by reconstruction are dynamic and responsive to forces acting on them. Each component of the system should function through the entire range of conditions to which it is exposed. Failure of the reclamation is a possibility if some of the conditions are not accounted for or if they are ignored.
References:
Terrence J. Toy and John P.Black, 2000, Topographic Reconstruction- Theory and Practice In: Reclamation of Drastically Disturbed Lands, Barnhisel R.J, Darmody R.G, Daniels W.L (Eds.), American Society of Agronomy, Madison Wisconsin, pp 41-76Munshower, Frank F, 1994, Practical Hand Book of Disturbed Land Vegetation, Lewis Publishers, 265 pp
Robert R.Stowe, 1996, Topography In: Handbook of Western Reclamation Techniques, University of Wyoming Office of Research, pp III-1 to III-19
Acid Drainage Water Source Control And Treatment Waste Source Control and Treatment Cyanide Treatment Waste Disposal Physical Stability Topographic Reconstruction Revegetation Air Prediction and Monitoring
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Last Updated : 03/18/04
