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• The drainage basin geomorphology of both the 006 and 005 Gulch basins have been <br /> investigated. Table 7-28 summarizes measurements of select geomorphic parameters for both <br /> gulches. The geomorphic parameters measured and presented in Table 7-28 were determined <br />for the drainage areas in each watershed above the confluences of each with the next order <br />stream (006 Gulch - confluence with Hubberson Gulch; 005 Gulch - confluence with Dry <br />Creek). The geomorphic data summarized in Table 7-28 indicate that the stream channels in <br />both basins are steep, exhibit moderate drainage density, and are of low sinuosity. The <br />drainage pattern in these basins is a combination of parallel and dend ri tic types. <br />Measurements of the cons to nce of channel maintenance (discussed in Brakensiek et al., <br />1979; and Mo ri Sawa, 1968) indicate that in the 005 Culch basin, .133 square miles of <br />drainage area are required to sustain one mile of stream channel; in the 006 Gulch basin, <br />.136 square miles of drainage area are required to sustain one mile of stream channel. <br />Although both basins exhibit similar drainage densities and elevation changes of their <br /> respective longest channels, the longest channel in 005 Culch is almost three percent more <br /> steep than the longest channel in 006 Cul ch. The average waters hed slopes calculated for <br /> both basins differ by less than two percent (Table 7-28). The shape of the 005 Culch <br />• basin is triangular, while the 006 Gulch basin has an elongated shape. These geomorphic <br /> data, taken together, are indicative of what is observed in the field: both basins <br /> exhib it similar geomorphic features, with the upper portions of each sloping steeply to <br />the west. <br />Stream channel longitudinal profiles, presented in Exhibits 7-7-i through 7-7-4, <br />illustrate gradients of major stream reaches in the northern (005 Gulch) and southern (006 <br />Gulch) mining areas. Inspection of these longitudinal sections indicates that the stream <br />profiles in both the northern and southern mining areas are generally concave with some <br />convex reaches. Convexity in these reaches is a result of bedrock control and deposition <br />of sediment load as ephemeral streamflow infiltrates the channel fill. A conclusion which <br />may be drawn from these longitudinal stream profiles is that both sediment erosion and <br />deposition are active processes in these two basins. <br />Table 7-29 presents stream channel gradients for select reaches of basins in the vicinity <br />of the Seneca II-W Mine. The reader should refer to Exhibits 13-4 and 7-1 for the <br />locations of each referenced reach of stream channel. From Table 7-29, it is evident that <br />. the main channels in both the 005 and 006 Cul ch basins are about six to seven times as <br />steep as Dry Creek, and are up to two times as steep as the upper channels of both <br />Hubberson and Watering Trough Gulches. <br />89 <br />