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r ~ <br />LJ <br />Stream Channel Parameters <br />Exhibit 55A and Changes Due to Mining-Induced Subsidence Pape 9 <br />would be maximized, this analysis has concentrated primarily on the Iower portion of each <br />stream segment. The computations were performed for the lowest channel reach within the <br />influence of the mining. <br />A principle of fluvial morphology, as confirmed by Manning's equation, is that the stream <br />channel chazacteristics described in Table 3 for channel width and depth will change as shown <br />below. <br />Channel Depth <br />Channel Width <br />Smaller <br />Slope Increase <br />Due to Subsidence <br />• <br />Slope Decrease <br />Lazger <br />Smaller <br />Lazger <br />• <br />The deformation of the ground surface due to subsidence results in a change in the existing <br />channel slope. The magnitudes of these slope changes were first computed based on the <br />subsidence model output, then the changes were applied to the existing channel slope to <br />determine the ensuing channel slope. For purposes of detemuning changes in channel hydraulic <br />characteristics, the channel slope neaz the confluence or mouth of each drainage was used so that <br />the contribution of the entire basin was included. <br />Due to Subsidence <br />Utilizing channel regime relationships developed by the geomorphic engineering profession, it <br />was determined that over a 3- to 5-yeaz period or more, the channel hydraulic chazacteristics <br />would change as shown in Table 5. The changes in depth and width are the maximum computed <br />values considering both a slope increase and slope decrease. However, it should be recognized <br />that the maximum changes in channel width and depth would not occur over the same channel <br />reach. <br />831-032.820 Wright Water Engineers, Inc. <br />