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Stream Channel Parameters <br />Exhibit 55 and Changes Due to Mining-Induced Subsidence Page 6 <br />• related evaluations. Channel profiles portraying the pre-mining slope and the range of slopes for <br />each stream segment are presented in Figures 3 through 18. <br />A summary of the stream channel hydraulic characteristics for each of the 16 drainage basins is <br />provided in Table 3. The slope in the lower reach of the channels is shown in addition to the <br />average channel slope since only the lower reach will receive the full basin runoff. <br />The dominant dischazge is that flow for [he stream which tends to shape the stream channel and <br />help establish the width and depth of the defined channel. The dominant discharge flow in cubic <br />feet per second for each basin is the peak flow expected to occur there once every two years. <br />Erosion and sediment yield of a stream basin is normally related to multiple factors, including <br />rainfall, ground cover, land use, topography, upland erosion, runoff, soil types. geology. <br />sediment, and channel hydraulic characteristics. All of these factors were considered. <br />The channel characteristics shown in Table 3 for the dominant discharge are for the stream near <br />. the mouth or at a pointjust downstream of each segment of stream channel. The width and depth <br />values at the dominant discharge in Table 3 are approximate values based upon computed <br />physical basin regime characteristics and identification of characteristics from photographs taken <br />on selected stream channels in the area. <br />The channel characteristics for Basin 2~, the upper part of Deep Creek, were refined based on <br />field observations conducted since the last revision to Exhibit ». These fteld observations show <br />the channel to be narrower and convey flows at higher velocities than predicted by the general <br />relationships. <br />The adopted mean annual runoff for the subject basins is used for sediment and channel stability <br />purposes only. It is no[ proposed for use in water rights studies or for site-specific water budgets. <br />• <br />Revised November 1999 <br />