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The BNRR embankment divides the flood plain downstream of the City of Fort Collins' Wastewater Treatment Plant Number 2. For the 10-, 2-, and I-percent annual chance floods, only the area of the right bank north of the railroad embankment was considered effective for flow. To develop water-surface elevations south of the railroad, a model was developed to consider the results of railroad embankment failure. For the O.2-percent annual chance flood, the split-flow option was used to calculate the flows that overtop the railroad embankment. The I-percent annual chance flood water-surface elevations south and north of the railroad embankment are shown on the same profile panels. There are two major flow diversions in the lower reach of the Cache La Poudre River. Between Cross Sections AE and AF (Sections 211017 and 212317 in the HEC-2 model) on the main channel, flow spills to the left-bank gravel pit area and flows along a separate flow path (referenced as Cache La Poudre LP A TH) before rejoining the main flow path just below the Fossil Creek Ditch diversion. The amount of flow diverted to LP A TH was computed using the split-flow routine from the 1989 SFH study. In the reach above the Timnath Reservoir Ditch diversion, the main flow of the Cache La Poudre River was modeled using two separate HEC-2 models. One model was for the 10-, 2-, and I-percent annual chance floods and the other was for the O.2-percent annual chance flood. In addition, there are several divided flows. Between Mulberry Street and Lincoln Avenue, the O.2-percent annual chance flood overtops Lemay Avenue on the left bank. This flow enters the drainage basin for Dry Creek and returns to the Cache La Poudre River below the Timnath Reservoir Ditch diversion. Just upstream of the Lincoln A venue bridge, flow splits and travels east along the north side of Lincoln A venue. 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 LINC. For the I-percent annual chance flood, less than 55 cfs continues east along Lincoln Avenue. A large drainage ditch runs along the north side of Lincoln A venue from just west of Lemay A venue east through the airport area. The small amount of flow not returning to the Cache La Poudre flood plain 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 I-percent annual chance flood discharge that would be lost east of Lemay A venue if the road embankment failed. The split-flow option in HEC-2 was used to calculate the spill, assuming normal-depth flow and no embankment. Using this discharge, another model was developed to compute the 1- percent annual chance flood water-surface profile downstream of Lemay and between Lincoln Avenue and Mulberry Street (referenced as Cache La Poudre LEMA YDS). This breakout spills over Lincoln A venue into the I-percent annual chance flood plain 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 O.2-percent annual chance 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 32