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<br />Figure 2.2.11. Pond at XS 6.1 <br /> <br />Figure 2.2.12. Low point in road and fire dept. tunnel <br /> <br /> <br />Water on the west side of the road should drain to the pond across this low point. In this way, <br />the flows on the west side of road due to overtopping of the weir at cross-section 14 from an <br />1800cfs flood should drain back to the channel at this point rather than continuing down the road <br />into downtown. However, during an 1800cfs flood, the constriction at cross-section 6 will cause <br />flood waters to rise above the low point of the road, and the fire department tunnel would still be <br />flooded even if the weir problem was corrected. <br /> <br />Windy Gulch Culvert <br />As mentioned earlier, Windy Gulch forms a sub-watershed within the Willow Creek watershed. <br />The creek bed enters Willow Creek just upstream of the Army Corps flume entrance approach <br />levees. Flow from Windy Gulch passes under the asphalted Bachelor Loop road through an <br />elliptical, corrugated metal culvert that is about 2.5 ft high by 4 ft wide. Large cobbles have <br />accumulated on the bottom of the culvert. <br /> <br />The hydrology of Windy Gulch is somewhat uncertain. The creek bed is normally dry, and a <br />large flood on the order of 200cfs would seem surprising. However, the watershed is fairly <br />large, and a heavy thunderstorm would probably overwhelm the sub-surface flow characteristics <br />of the watershed. The best hydrologic estimate appears to be the rainfall/runoff estimate by <br />Water Management Consultants as discussed in Section 2.2.2, but further study is needed. <br /> <br />A separate model was created in HEC-RAS to analyze flood flows in the Windy Gulch culvert. <br />Figure 2.2.13 shows HEC-RAS results at the upstream end of the culvert (XS 2) using the <br />rainfall/runoff hydrology from Water Management Consultants. The culvert is undersized to <br />pass high flood flows, and the roadway will be overtopped during flood events in Windy Gulch <br />initiating at the 10-year level. The pattern of flow overtopping the roadway is multi-dimensional <br />and difficult to model using a one-dimensional model. Several model configurations were used <br />to examine the flow, but a two-dimensional model would be needed to accurately delineate <br />flooding. The majority of flow overtopping the road should reenter Willow Creek just upstream <br />of the flume entrance approach levees. However, a portion of the overtopping flow will <br />probably flow down the road towards downtown Creede. Figure 2.2.14 shows the expected <br />areas of flood inundation as well as topographic survey points and model cross-sections. Arrow <br />shapes indicate water from Windy Gulch expected to flow south towards downtown Creede and <br />north towards the Fire Department tunnel. <br /> <br />2-25 <br />