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II -9- -10- II II , I flood hazard area does not correlate with the flood profile, and a dashed line has been added to the plan to indicate the limit of flooding corresponding to the profile. ln all cases, the flood profile computations below spill areas are based on the entire flood remaining in the channel. include open space and residential. Near the upper Highway 48 II crossing, a private residence area, and just downstream of outbuildings are included. The feet in width, channel velocity is within the flood hazard South Eldridge Street, four flood hazard area averages 163 is average 8.3 fps. feet. The At the middle and downstream crossing of Highway 48, and at South Eldridge Street, a portion of the 100-year flood flows parallel to the roadway and embankments instead of along the channel profile. The flood overtops the roadway embankments, returning to the channel as it goes. These si tuations are shown on Sheets 4, 5 and 6 of the drawings. At the most downstream crossing of Highway 48, also known as West Bellevue Avenue, approximately 160 cfs of the 100-year flood do not return directly to Weaver Creek. The water flows eastward at shallow depths toward the Bergen Reservoir return, shown on the Rasin Map. It is intercepted by the return and is directed, eventually, back to Weaver Creek. At the Cole Street bridge, approximately 100 cfs leaves the channel and flows in Cole Street and Youngfield Avenue. It returns to the channel at the Youngfield Avenue bridge. I II This study defines the 100-year floodway of Weaver Creek, where the design flows are not confined within a well-defined channel. The floodway criteria of Jefferson County has been utilized. The floodway exists whereever depths are greater than one foot, or velocities exceed three feet per second. FloGdway data are keyed to cross-sections, and are summarized in Table 5. II I J I I flood Hazard Area Descri~on II I for the reach of Weaver Creek from the upstream limits of the study to the upper crossing of Colorado Highway hazard area is relatively narrow, averaging 100-year flood overtops six private drives, two small darns, four local roads within the Willowbrook subdivision, and 48, 141 the f1 ood II II I ~ Highway 48. Below some of these crossings, areas of shall ow overland flow are included in the flood hazard area. Areas of shallow flooding could exist below the Bergen Ditch. II Land uses within the region include primarily open space and recreation. One outbuilding, portions of a horse stable, a t enni s court and a gal f course are wi thi n the hazard area. Existing (1976) devlopment is large lot residential. and plenty of room h~s been left for passage of the flood. Channel velncities average 5.9 fps and overbank velocities, where they exist, average 2.3 fps. An improved channel has been constructed in the reach from above Cole Street to Simms Street. This channel is generall y adequate to convey the 100-year flow, except for an area in the Harriman Park Subdivision near Van Gordon Way, where a small amount of water may leave the channel and flow in the street. At the intersection with the Harriman Canal, a dike is being constructed to restrict flow to the channel. 11 I ! I At the culvert time of the original mapping (1976), under South Simms Street could not be the existing located. Sub- II In the reach from the upper crossing of Colorado Highway 48 to West Quincy Avenue, land uses within the flood hazard area sequently a 48-inch culvert was installed. Its potential capacity is small and it was not included in the hydraulic calculat Lons. The lOO-year flood overtops South Simms Street at West Quincy Avenue. II ~ leonard Rice Consulting Water Engineers, Inc ~ leonard Rice Consulting Water Engineers, Inc.