Laserfiche WebLink
Stream Channel Parameters <br />Exhibit 55A and Changes Due to Mining•Induced Subsidence Page 2 <br />EXISTING STREAM CHANNEL CHARACTERISTICS <br />The existing stream channel characteristics have been defined for various parameters, including <br />channel slopes, peak flow rates for a variety of frequencies of occurrence, flow velocities for <br />each of the frequencies, sediment transport regime, stage-discharge relationships, channel <br />profiles, and channel and over-bank stability. <br />The existing channel shapes were related to the dominant discharge (2-yeaz frequency of <br />occurrence). Sediment transport has been defined for each stream using the annual sediment <br />load; however, sediment transport is a long-term value and represents the full range of flows <br />including the 10-yeaz and 100-yeaz frequency peak dischazges. <br />For each of the 11 existing stream channels, many hydrologic and stream channel parameters <br />were defined and evaluated, including: <br />• 1. Mean annual runoff <br />2. Peak discharges for the 2-yeaz, 10-yeaz, and 100-year frequency floods <br />3. Mean annual sediment yields <br />4. Average thalweg~ slopes <br />5. Channel chazacteristics for the dominant discharge (consisting of width and depth <br />relationships) <br />6. The range of the channel slopes from near mouth to upper reach <br />Other factors that influence the long-term channel chazacteristics include the forested azea and <br />frequency of landslides. <br />BASIN HYDROLOGIC CHARACTERISTICS <br />WWE and Mr. Pemberton evaluated and studied each of the 11 stream segments and their basins <br />• Z Line following lowest part of a valley, i.e., invert of channel. <br />DRAFT <br />