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Stream Channel Parameter; <br />. Exhibit SSA and Changes Due to Mlning-Induced Subsidence Page 8 <br />channels ranging from a maximum increase of 1.9 percent to a maximum decrease of 1.7 percent. <br />These slope changes will be insignificant on the stream channels where existing average slopes <br />range from 5.3 percent to 18.4 percent. <br />The Dry Fork above Minnesota Reservoir (Basin 35) is the receiving water body for Basins 4 <br />through 6 and 26 through 33; Basin 34 is tributary to the Dry Fork below Minnesota Reservoir. <br />The channel thalweg for the Dry Fork spans multiple E Seam panels. Maximum subsidence <br />along the stream profile is approximately 9.3 feet. Channel slope in the lower reach is upwazds <br />of 5.6 percent and average slope for the entire reach is approximately 5.3 percent. Slope changes <br />due to mining subsidence will range from a minimum of -1.5 percent to a maximum of 2,0 <br />percent. Figure 17 depicts the pre-and post-mining stream profiles and demonstrates the overall <br />channel slope is not significantly impacted by subsidence. <br />• CHANGES IN STREAM CHANNEL HYDRAULIC CHARACTERISTICS <br />The channel characteristics for each of the basins (as shown in Table 3) were then analyzed using <br />geomorphological and sedimentation engineering relationships and formulas to detemune the <br />extent and type of change to each channel segment and then to estimate the amount of sediment <br />yield change. <br />Hydrologic review has determined that the following basin chazacteristics will not change <br />significantly as a result of subsidence: <br />1. Mean annual runoff <br />2. Peak dischazge <br />3. Dominant dischazge <br />4. Forest cover <br />• <br />Due to the fact that the mean annual runoff, peak dischazges, and the dominant dischazge aze <br />greatest for the lower end of each stream segment studied, which is where the channel changes <br />831-032.620 Wright Water Engineers, Inc. <br />