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6 omitted. The 25-year design storm vas input starting with the sixth hour and ending with the sixteenth hour for a total duration of eleven hours. Similarly, the 100-year hyetogzaph vas input starting with the fifth hour and ending with the seventeenth hour for a total duration of thirteen hours. 2.2 Ground Cover and Impervious Areas The main influence on ground cover in the study area is on flow resistance ' and not on interception potential. The MULTSED physical process model is quite • sensitive to the gmund cover density. After applying the MULTSED model, it was found that the ground cover densities had to be reduced for the present- . mining condition of the Magpie Creek watershed. The densities were reduced by f five percent from tha values that were presented in the Preliminary Data Base Report. The densities were reduced so that the peak discharge at the watershed r outlet vas within a range estimated by regression equations (Section 5.1). Table 1 presents the adjusted ground cover densities used in the MULTSED physical process model for present-mining conditions. In the Preliminary Data Base Report, no impervious areas were assumed for the Magpie Creek watershed for either the present- or post-mining condition. Since many of the upper subwatersheds do contain exposed rock outcroppings, a value of five percent impervious area was assigned to them. The sulraatersheds which were given impervious area are SW-4, SW-5, Sit-6, SSi-7, and SW-B. 2.3 Sediment Siza Distribution After applying the MULTSED physical process model and inspecting photo- graphs, it vas determined that CH-17 could not be accurately represented by the sediment size distribution of the Magpie Creek diversion as presented in the Preliminary Data Base Report. There are larger sediment sizes on the downstream end of the Magpie Creek diversion channel than in the middle and upper end. A size distribution was developed for CM-17 with information from photographs and site inspections. The sediment size distribution that was used for CH-17 is presented in Table 2. . 2.4 watershed Segmentation and Geometry The watershed segmentation and geometry for the present- and post-mining conditions vas presented in the Preliminary Data Base Report. The schematic flow diagrams of the watersheds are also presented in this report for reference.