Geomorphic reclamation approximates the slopes, drainage divides, and stream geometries of the pre-mining topography and is encouraged to ensure slope stability and reduce stream sediment. . Channel length is measured along the thalweg - the deepest point of the channel which is also the line of fastest water flow (steepest descent). Channel length is the single most important measure of geomorphic reconstruction but the watershed area, shape, and placement are also vital for reclamation success. (VIP 11) Using a GIS “watershed tool”, watersheds and associated drainage patterns can be delineated from a DSM. The inspector can compare reconstructed drainage patterns (depicted with a heavy black dashed line in the figure below) derived from the current DSM to the drainage reconstruction plan in the approved permit.
Watershed tools allow the inspector to interactively pick “pour points” (watershed discharge points) to identify and label the contributing watersheds. The resulting watershed delineations are shown in blue in the drainage reconstruction figure below. This GIS application allows the inspector to compare the reconstructed watersheds to the plan to determine if the new geomorphology complies with the permit.
Drainage Reconstruction at the McKinley Mine site.