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<br />roadway will be overtopped during flood events initiating at the 1 a-year level. A portion of the <br />overtopping flow will flow down the road and potentially cause flooding in downtown Creede. <br /> <br />Entrance to Army Corps Flume <br />The Army Corps constructed large levees to guide flood flows into the masonry flume. Flooding <br />and overbank flows caused by Willow Creek should re-enter the forebay upstream of the levees, <br />be contained by the levees, and enter the masonry flume. However, flooding originating from <br />Windy Gulch may circumvent the levees and flow towards downtown Creede. In addition to the <br />Windy Gulch problem, a small modification to upper end of the approach levees is needed to <br />ensure a three-foot freeboard in the levees. This amount of freeboard is often required by the <br />Army Corps in order to recognize that downstream structures are not located in the floodplain. <br /> <br />North Creede Culvert <br />The hydraulic analysis indicated that the culvert in North Creede will be overtopped in nearly all <br />flood events. Personal accounts of flooding indicate that floods typically erode the roadway near <br />the culvert. A large flood will probably damage surrounding structures. <br /> <br />West Willow Creek Culvert <br />The Bachelor Loop road crosses a culvert just upstream of the concrete bridge below the <br />Commodore Mine. Hydraulic analyses show that the culvert will cause overtopping of the <br />roadway parking area during the lOa-year flood, although plugging of the culvert by debris will <br />probably cause flooding during a smaller flood. The overbank flooding may cause localized <br />damage to the road, but should reenter the channel downstream of the culvert. <br /> <br />Commodore Mine <br />A flume and metal pipe carry West Willow Creek over and through the large Commodore mine <br />tailings pile. Hydraulic analysis indicated that the Commodore pipe system cannot pass high <br />flood flows. The 1 a-year event will cause flooding of the depressed area at the pipe entrance. A <br />25-year flood will overtop the tailings pile, causing a high velocity flow down the very steep face <br />of the pile. This event could potentially erode tons of mine tailings and mine debris into Willow <br />Creek. Fine tailing sediments would probably be carried by the flood into the Rio Grande. <br /> <br />Amethyst Mine Culvert <br />The hydraulic analysis showed that the lOa-year flood should cause overtopping of the culvert. <br />However, debris will probably plug the "grizzly" grating in front of the culvert at a much smaller <br />flow and cause damage to the entrance to the Amethyst Mine and surrounding tailings areas. <br /> <br />Watershed Conditions <br />The physical characteristics of the Willow Creek watershed were quantified in GIS using the <br />DEMs and vegetative studies from the u.S. Forest Service. Maps representing the slope, <br />primary cover type, percent forest, and percent of barren land were produced. <br /> <br />Specific sediment sources in the Willow Creek watershed that may be contributing sediments to <br />the Willow Creek channel were identified using aerial photography and delineated in GIS. <br />Mapped sediment sources included areas of mine tailings, mine related disturbance, mobile <br />talus/scree, and roadways. <br /> <br />111 <br />