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<br />2.3.2 Watershed Sediment Sources <br /> <br />Specific areas in the Willow Creek watershed that may be contributing sediments to the Willow <br />Creek channel were identified in the USGS DOQQ and the infrared photos, and delineated in <br />GIS. Portions of the Willow Creek watershed have been highly affected by historical mining <br />activity. The majority of sediment sources that were identified were located in the lower reaches <br />of East and West Willow Creeks. Figure 2.3.2 shows primary watershed sediment sources that <br />were identified in this area. <br /> <br />Even if undisturbed, the watershed would obviously produce a significant sediment load from <br />natural processes. Erosion of solid rock canyon walls has produced large areas of talus and scree <br />on steep slopes that are unprotected by vegetation. Many of these scree areas could not naturally <br />support trees or other vegetative cover, although the effects of historical timber harvesting may <br />still have some influence. Scree/talus slopes that appeared unprotected, highly mobile, and able <br />to directly contribute sediments to the Willow Creek channel were mapped in Figure 2.3.2. The <br />majority of these areas exist below the Amethyst Mine on West Willow Creek and below the <br />Phoenix Mine area on East Willow Creek. Many talus slopes do exist above these slopes or <br />higher in the watershed, but only slopes that appeared to have a close, direct connection to the <br />stream channel were mapped. <br /> <br />The sediments in mobile, unprotected scree/talus slopes are large; typically from large gravels to <br />boulders. Although natural sediment production is expected, disturbances by man in the <br />watershed may expose finer and more mobile sediments. <br /> <br />A large number of roads have been built in the Willow Creek watershed related to mining, <br />timber, and building activities, and they were mapped. These roads could be a source of fine <br />sediments, particularly when built on steep slopes, or built with elevated steep banks near the <br />stream course. Mine tailings piles that could be identified in the photography were also mapped. <br />Most tailings piles have no vegetative cover and sediments are often much finer than natural <br />surrounding sediment sources. Therefore, mine tailings can be mobilized and easily transported, <br />particularly if located on steep slopes. Obviously, sediments from mine tailings piles may also <br />pose additional, significant water quality risks if they were to enter the channel systems. Fine <br />sediments could degrade fish habitat as well as increase acidic or heavy metal loadings. Finally, <br />areas that were notably disturbed from their natural state were also mapped. Most of these areas <br />were associated with mining activities, although streambed and building construction <br />disturbances were also mapped. These disturbance activities often resulted in damage to <br />vegetative covers, an un-consolidation of sediments that may make them more mobile, or <br />exposure of finer sediments. <br /> <br />2-39 <br />