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<br />. <br /> <br />. <br /> <br />. <br /> <br />The differences in 500-year water surface elevations between Cross Sections AP:224597 <br />and 229997 are attributed to correcting two inconsistencies in the original 1994 analysis [SLA, <br />1994] : <br /> <br />. The lack of iteration between the JP.5 = 99% (JP Card, Field 5) field in the <br />UPPER500IDEUQ506 model and the actual flow (Qsoo = 3,466 cfs or 89% of the <br />total Q) returning to the main chmmel over Lincoln Avenue from the LINC DFP <br />as computed in the LINC model (DELINC06). <br /> <br />. An error in the WS.3 (WS Card, Field 3) input to the original HEC-2 hydraulic <br />model named UPPER500. The WS.3 field referenced Cross Section 228125 <br />instead of Cross Section 228117. Therefore, the second lateral weir between main <br />chmmel Cross Sections AS:228117 and 227437, computing spills to the LINC <br />DFP, did not work properly. <br /> <br />Minor changes (approximately 20 cfs) in the SOO-year discharges along the main chmmel <br />between the Dry Creek confluence and the Tinmath Diversion Dam as a result of combining the <br />Upper and Lower Reach models were noted. Reporting and delineating corrected effe:ctive 500- <br />year water surface elevations downstream of the Tinmath Diversion Dam were Gonsidered <br />outside the scope of the current study. <br />The 500-year discharges in the LINC DPP model [CELINC06] were updated during the <br />corrected effective analysis. A comparative summary of the duplicate and corrected 500-year <br />water surface profiles along the LINC DFP is presented in Table 5.2. A comparative: summary <br />of the duplicate and corrected 500-year discharge profiles along the LINC DFP is presented in <br />Appendix D.1. <br />The corrected effective 100- and 500-year floodplain delineations are shown on Sheets <br />2A and 2B. As requested by the City of Fort Collins, two Letter of Map Amendments (LOMAs) <br />(FEMA Case No.s: 01-08-153A and 02-08-485A) have been incorporated into the corrected <br />effective mapping. The LOMA properties are located on the south side of Lincoln Avenue <br />approximately 1000 feet east of the Cache la Poudre River. Copies of the original LOMAs are <br />located in Appendices B.2.1 and B.2.2. <br />Corrected effective water surface profile plots are located in Appendix C.2. The <br />input/output HEC-2 reports for the corrected effective floodplain analyses are provided in <br />Appendix G. A digital copy of the HEC-2 models utilized for the current study is provided on <br />the disk included with this report. <br /> <br />eOFC2003-1O Oxbow FINAL LOMR,doc <br /> <br />5.3 <br /> <br />ANdERSON CONsulTiNG ENGiNEERS, INC. <br />