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2.2.3. Drainage Density Analysis <br />• Drainage density was defined by Horton (1945) as the sum of all <br />channel lengths within a basin divided by the basin area. It is a <br />measure of the efficiency with which water is removed from a basin by <br />the drainage network. The NOV cites several locations where unapproved <br />drainage valleys have been constructed where none existed before and <br />that this does not constitute approximate original contour. In <br />geomorphic terms the ~OV states that the addition of unapproved drainage <br />ways constitutes a change in drainage density between approved and <br />existing topography, and furthermore, that the change is inappropriate <br />and does not achieve AOC. Measurement of drainage density on approved, <br />existing, and adjacent unmined topography provides an objective insight <br />into whether reclamation by CYCC has changed drainage density and <br />• whether the change, if any, is significant. <br />Drainage basins were delineated on existing and approved mine maps <br />at a scale of 1 inch equals 500 feet. Basin boundaries do not coincide <br />exactly with mine areas and in most cases they are outside the mine <br />areas. In addition 11 basins outside the mine area on similar litho logy <br />and topography were delineated on the Rattlesnake Butte USGS quadrangle <br />at a scale of 1:24000. The drainage networks on the maps were <br />delineated by following contour crenulations (notches or "v" shaped <br />indentations) up the basin until they were no longer visible. Aerial <br />photographs were used to ensure that the drainage networks on the USGS <br />quad maps were extended as far as networks on the mine maps. <br />Drainage density of the approved topography is 3.3 miles per square <br />• mile and far existing topography it is 4.0 miles per square mile. <br />14 <br />