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Just upstream of the Lincoln Avenue bridge, flow splits and travels east along the north side of Lincoln Avenue. Much of the split flow spills back across Lincoln Avenue to the Cache La Poudre River along the flow path referenced as Cache La Poudre LINe. For the loo-year flood, less than 55 cfs continues east along Lincoln A venue. A large drainage ditch runs along the north side of Lincoln A venue from just west of Lemay Avenue east through the airport area. The small amount of flow not returning to the Cache La Poudre floodplain is collected by this ditch. A normal-depth analysis shows this ditch could carry a discharge of 55 cfs. The flow in this ditch eventually enters Dry Creek. A separate HEC-2 model was created to calculate the Ioo-year discharge that would be lost east of Lemay A venue if the road embankment failed. The split-flow option in the HEC-2 model was used to calculate the spill, assuming normal-depth flow and no embankment. Using this discharge, another model was developed to compute the 100- year water-surface profile downstream of Lemay and between Lincoln A venue and Mulberry Street (referenced as Cache La Poudre LEMA YDS). This breakout spills over Lincoln Avenue into the 100-year floodplain of Dry Creek and returns to the Cache La Poudre River via that stream. The discharge in the main channel of the Cache La Poudre River was not reduced for the loss of flow through the Lemay A venue breakout due to the low probability of road- embankment failure. At the upstream side of the BNRR bridge, the 500-year flood flows east along Vine Drive. The amount of flow that spills was determined from a rating curve for normal- depth flow over the control section at this location. The spill along Vine Drive flows into the drainage for Dry Creek and returns to the Cache La Poudre River below the Timnath Reservoir Canal diversion via Dry Creek. Downstream of Taft Hill Road, there are two diversion structures (for Larimer-Weld Canal and Arthur's Ditch) and large excavations on both sides of the river. Most of the effective flow was on the left bank during the IOO-year flood due to the protective berms. Upstream of Taft Hill Road, split flow occurs during the 500-year flood. The same Manning's "n" value of 0.035 for the channel in the 1989 study was used for this restudy. For the overbank areas, the values were revised to reflect existing conditions. The values for the overbanks range from 0.04 to 0.104. Starting water-surface elevations for the main channel of the Cache La Poudre River were taken from the 1993 Flood Insurance Study report for Larimer County, Colorado (Reference 30). For the reach of the Cache La Poudre River identified as Interslate Highway 25 Divided Flow, flows during the 50-, 100-, and 500-year events become separated from the main flow by the embankment for 1-25. The divided-flow path extends southerly along the west side of 1-25, before crossing 1-25 and returning to the main flow path. There are two locations where water splits away from the divided-flow path and returns to the main path. The divided-flow path was modeled using HEC-2. The roughness coefficient for the channel was estimated as 0.035 and the overbank "n" values ranged from 0.043 to 15