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topographic variations similar to the top of the mine. A typical <br />• profile of the upper portions of area 9/10 and a profile plotted from <br />topographic maps of the dip slope north of the mine show landforms of <br />similar shape and scale (Fig. 2.6). In both cases profiles show a <br />reverse in slope direction some distance from the top of the hill. <br />Although a reverse in pre-mine slope did not occur on the mine area the <br />fact that it does occur on an adjacent dip slope of the same geologic <br />formation suggests that such a landform is not inconsistent with respect <br />to the natural landscape. <br />2.3. Geomorphic Stability Comparison <br />Natural landforms can be identified that undergo rapid change as <br />indicated by rilling, gullying, or other forms of excessive erosion. <br />• Similarly, landforms can be identified which exhibit little or no <br />change. By measuring characteristics of landforms it may be possible to <br />characterize the relative stability of topography. Furthermore, <br />landforms can be compared only if they are comprised of similar <br />materials in areas of similar climate. <br />2.3.1. Natural Hillslope Gradient <br />Oversteepened slopes relative to approved topography in the upper <br />portion of the Swale in areas 9/10, 7, and 31 are cited in the NOV. In <br />order to compare the stability of these slopes with approved slopes, <br />their gradient was compared to natural, stable slopes composed of <br />similar materials. The natural slopes selected are colluvial (or <br />• <br />17 <br />