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• SVeam Channel Parameters Exhibit 55A and Changes Due to Mining-Induced Subsidence Page 6 STREAM CHANNEL HYDRAULIC CHARACTERISTICS The stream channel regime and characteristics were defined using still photographs, videotapes, USGS topographic maps, detailed topographic maps prepazed for the mine azea, soil surveys, geological evaluations prepazed by John Rold (consultant to WWE), aerial photographs, and related evaluations. Channel profiles portraying the pre-mining slope and the range of slopes for each stream segment aze presented in Figures 3 through 14. A summary of the stream channel hydraulic chazacteristics for each of the 12 drainage basins is provided in Table 3. The slope in the lower reach of the channels is shown in addition to the average channel slope since only the lower reach will receive the full basin runoff. The dominant dischazge is the flow for the stream that tends to shape the stream channel and help establish the width and depth of the defined channel. The dominant dischazge flow in cubic feet • per second for each basin is the peak flow expected to occur there once every 2 years. Erosion and sediment yield of a stream basin is normally related to multiple factors, including rainfall, ground cover, land use, topography, upland erosion, runoff, soil types, geology, sediment, and channel hydraulic chazacteristics. All of these factors were considered. The channel chazacteristics shown in Table 3 for the dominant discharge aze for the stream neaz the mouth or at a point just downstream of each segment of stream channel. The width and depth values at the dominant dischazge in Table 3 aze approximate values based upon computed physical basin regime characteristics and identification of chazacteristics from photographs taken on selected stream channels in the azea. The adopted mean annual runoff for the subject basins is used for sediment and channel stability purposes only. It is not proposed for use in water rights studies or for site-specific water budgets. 831-032.620 Wright Water Engineers, Inc.