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I, - MODW^, ,- FRINGE l00-VEAllfLOODPLAIN .1 HOQOWAY LOOOWAY FlllNGe STM:AM CHANNEL HOOOHEVATIONWHI!N CONfIN!;OWlTHINFLOOOWAY A.Re"OF FLOODPlAIN '......'COVLD IE IJSED FOil Df,."nOPMENT 1'1' RAlSI'< LINE AS IS THE flOOD ElE\lATION IEFOItE ENCIlOACHMENT UNE CDIS THE fLOOD itEVA nON ..FlER ENCROI'o.CHMENT ~URCHARGE IS HOT TOEXCEEO 1.0 FOOT(AA 'f(QUIREMENnOIl u<sseRAMQUNllFSpeClfIEO II' STATE Figure 2. Floodway Schematic In the lower reach of the Cache La Poudre River study, divided floodways were developed along the Cache La Poudre River and Cache La Poudre LPATH due to split- flow conditions. Just east of Wastewater Treatment Plant No.2, the main flow of the Cache La Poudre River leaves its channel during the large-flood events. The floodway was delineated along the breakout flow path. No floodway was mapped for the Lowflow channel of the Cache La Poudre River. Just below Taft Hill Road, a flow diversion was modeled by subtracting the left overbank flow from the tolal discharge and confining the remaining flow to the channel. It was assumed that the confining banks fail for the purpose of computing a floodway. A I -foot-rise floodway was computed for Spring Creek based on a combination of equal conveyance reduction and by setting the encroachment slations at specified locations. The flood way along Dry Creek was developed using the equaI-conveyance methodology (Reference 30). A floodway was added to the main channel of Cooper Slough and the East Island Divide from East Vine Drive downstream to the C&SRR. These floodways were based on the equal-conveyance method. A floodway was not added downstream of the C&SRR because of the.Qumerous breakouts along the lower reach of the slough. A floodway was not developed for the Boxelder Creek Overflow Channel because of the complex flow conditions (Reference 30). 31