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I I I I I I I I I I I I I I I I I I The Flatirons Gravel Pit and Levee pushed the West Overflow towards South Boulder Creek (see Drawings 5 and 6). Without the levee, most of the West Valley Overflow would have flowed directly to the west of the foothills and Highway 36 Interchange. Regardless of the levee, significant portions of flows in South Boulder Creek just upstream of Highway 36 overflow to the West Valley, and potentially flood the urbanized area downstream. South Boulder Creek downstream of Highway 36 to Arapahoe Road is largely natural (Sheets 6, 7, and 8). The floodplain downstream of the Wellman Ditch is developed and is the location of another split to the West Valley (Sheet 7). While the stream is natural here, it shows signs of aggregation from sedimentation, overgrowth, and resultant loss of capacity. Downstream of Arapahoe, South Boulder Creek is largely channelized. The West Valley downstream of Highway 36 is urbanized, largely residential with some commercial near Foothills and Baseline, and along and downstream of Arapahoe. Flood waters take many routes as illustrated on the drawings. The main overflow path starts downstream of Highway 36 on the west side of Foothills and travels northerly to the intersection of Baseline and Foothills. At the intersection, flows split in seven directions. Three paths follow Foothills to Wellman. While these flows are shown in the modeling entering the Wellman, the two roadway flows will largely leave the basin and enter Bear Canyon Creek or Boulder Creek. At the same time, Wellman Ditch flows from the west will enter as a transbasin flow, but the model, per contract, assumes no flows. There are probably some offsetting effects. That is, the Wellman brings flow in from Bear Creek while the flows on Foothills go to Bear Canyon, Two of the flows from the Foothills and Baseline intersection follow Baseline. The last two are conveyed over and under Baseline, and join the Baseline flows after going through a minor storage, except for a small portion that crosses under Baseline to the drainage ditch on the north side (the Crossover Ditch). Numerous flows and subsequent spills on and from Baseline travel northerly through the Country Club Park, Centennial Trails, Arapahoe Ridge, and commercial areas to the north. Much of the flow on the west side of 55th will spill northwesterly to Boulder Creek through the commercial area. The overflows on the golf course drain to Dry Creek Ditch No.2, which is a large channel to the north of Arapahoe, then join South Boulder Creek flows and discharge to Boulder Creek. 1-3