Laserfiche WebLink
Stream Channel Parameters and Changes <br /> Exhibit 55B Due to Longwall Mining-Induced Subsidence Page 11 <br /> of characteristics from photographs taken on selected stream channels in the area. <br /> In 2020, WWE performed work relating to the South Prong stream channel through which we <br /> gained site-specific knowledge of the hydraulic characteristics. As a result, we have updated our <br /> channel geometry and refined our analyses of potential effect of longwall mining to incorporate <br /> this experience. <br /> The width to depth ratio, floodplain connectivity, substrate material, and channel slope provide an <br /> understanding of the geomorphic context of the study stream systems. The hydraulic <br /> characteristics provided in Table 3 result in existing width-to-depth ratios of 12 and 4 for South <br /> Prong and Lion Gulch,respectively. As typically observed in headwater systems,the steep terrain <br /> surrounding each study reach sets both streams within a confined valley. A confined-valley type <br /> results in channels that are relatively entrenched, with little to no access to a broad floodplain. <br /> Similarly, the existing terrain results in steeper channel slopes and stream substrate that can <br /> withstand the higher velocities associated with the steep terrain. Together, these hydraulic and <br /> geomorphic characteristics indicate that both study reaches consist of cascading stream channels <br /> within the steeper sections and step-pool channel morphology where channel slopes are less than <br /> 4%. <br /> 831-032.921 Wright Water Engineers, Inc. <br /> December 2020 <br />