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<br />Upper Willow Creek Above Flume <br />Figure 2.2.4 (next page) shows flood inundations for the area between the flume entrance and the <br />weir at cross-section 14. Overbank flooding is mapped for various return intervals. The flood <br />level corresponding to the maximum designed capacity of the Army Corps flume (1800cfs) was <br />also mapped. Only the 100-year flood level is indicated within the main channel on the eastern <br />side of the canyon, as delineation of other intervals is indiscernible at this scale. <br /> <br />Downstream of cross-section 14, the main channel is contained against the eastern wall of the <br />canyon by push-up levees. Overbank flooding initiates at the weir at cross-section 14 at the 25- <br />year flood level, at cross-sections 8.5 and 6.1 at the 1800cfs level, and at the Windy Gulch <br />culvert at the 10-year level. Flood overbank flows originating upstream of Windy Gulch should <br />re-enter the flume approach levees and be directed into the masonry flume. Flood flows from a <br />very heavy thunderstorm in Windy Gulch will probably flow into the downtown area of Creede. <br /> <br />Overtopping of Weir at Cross Section 14 <br />An earthen and wood weir alters the course of <br />Willow Creek at cross-section 14. Wooden <br />planks on the north, and timber cribbing on the <br />south contains an earthen dam. The dam is <br />oriented at nearly a 45-degree angle to the flow <br />of the creek, and a wood weir passes water to <br />the current channel location at the very eastern <br />edge of the canyon. Much of the wood has <br />deteriorated and may be damaged under flood <br />conditions. Photos of the weir follow. <br /> <br /> <br />The severe angle and constriction of the weir <br />will cause floods to overtop the earthen/wooden <br />dam. Lower elevation areas at the east and <br />west ends of the dam will be overtopped by the <br />25-year flood, while the entire dam will be <br />overtopped at the 100-year flood level as shown <br />in Figure 2.2.7. Flood flows will enter the <br />depression west of the main channel and flow <br />downstream into the parking area east of the <br />mining museum. A photo follows that shows <br />the path of overbank flooding. Water can <br />reenter the channel through the small pond at <br />cross-section 7, and, to a lesser extent, through a low levee section at cross-section 8.5. The 100- <br />year flood should not cross the road. However, the 1800cfs flood should cross the asphalted road <br />at about cross-section 8. This would result in flooding to low sections of the mining museum / <br />community center as well as the entrance to the fire department tunnel. Water that crosses the <br />road from the 1800cfs flood should re-cross the road at a low point near cross-section 6.1 and <br />enter the flume approach levee and flume. Failure of the deteriorated earthen dam and weir upon <br />overtopping is probable and could cause increased flooding at lesser flood return intervals. <br /> <br />2-22 <br />