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basin and its principal channel. Thus, premine principal channel widths and associated flood plains will be <br />approximated to the extent practicable, given the limits of available equipment. However, in no event will <br />principal channel widths be less than premine channel widths. Also, all principal channels will be con- <br />structed to prevent short-circuit or capture by an adjacent principal drainage channel for a 100 -year, 24- <br />hour event in large watersheds and a 10 -year, 24-hour event for small (less than one square mile <br />drainage area) watersheds. <br />The length of the drainage route may be increased such that the overall gradient is lowered. By <br />approximating the premine drainage area, lateral adjustments of the drainage routes as necessary to <br />maintain an appropriate gradient are not expected to have adverse consequences on geomorphic stability. <br />Further, by lengthening the course of the drainage, the rate of flow may be reduced, thus promoting <br />drainage stability. <br />The above goals will be achieved as shown on the postmining topography map, (Map M12). Pre -mining <br />and approximate postmining profiles for a representative areas are shown on Map M -14A, Postmining <br />Profiles. Profile locations are shown on M12. Section 4.8.1.3 discusses stabilization once regrade activi- <br />ties are complete. <br />Any temporary diversions constructed around a drainage will be eliminated upon completion of the mining <br />operations in the affected area. As can be seen from the postmining topography map, Map M12, the <br />topography of the surface mined land after regrading will be supportive of the postmining land use of stock <br />grazing, some farming, and wildlife habitat. <br />3-43a <br />'4joq <br />Pk(p <br />II2Ifof <br />