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<br />. <br /> <br />. <br /> <br />. <br /> <br />VI. <br /> <br />EXISTING CONDITION HYDRAULIC ANALYSES <br /> <br />The existing condition analysis was required to update the corrected effective analyses <br />with changes to the floodplain, which occurred prior to construction of the current project as <br />documented in the revised condition. In order to regulate local ordinances tied to the Cache la <br />Poudre River's 500-year floodplain, the City of Fort Collins requested that the left overbank 500- <br />year floodplain between the RN.R.R. and Lincoln Avenue be updated. The existing condition <br />analysis incorporated new topography collected since the date of the effective study. In addition <br />to better detail, the new topography included man-made physical changes, which were <br />constructed after the date of the effective study; therefore the information was included in the <br />existing condition rather than the corrected effective condition. The corrected effective HEC-2 <br />models were modified accordingly in order to evaluate the existing condition. <br />The existing condition analysis utilized topographic information from the 1999 City of <br />Fort Collins topography, the 2004 King Survey Inc. (KSI) topography, and spot elevations <br />obtained by KSI in February 2006. The KSI 2004 topography and 2006 spot elevations are <br />located in Appendix R3. <br />The existing condition analyses updated the LINC DFP 100- and 500-year discharges and <br />floodplain delineations. Updating the LINC DFP resulted in changes to the main chmmel <br />discharges; therefore the existing condition analysis also updated the 100-year floodplain, 500- <br />year floodplain, one-foot floodway, and tenth-foot floodway analyses along the Cache la Poudre <br />River's main chmmel. <br /> <br />6.1 FEMA Analyses <br /> <br />The existing condition FEMA models for the current study are similar to the corrected <br />effective models however, an 'EX' has been added as the prefix to each model's name <br />(EXI00Q06, EX500Q06, EXIFW06, and EXLINC06). <br />The starting water surface elevations for each existing condition model were identical to <br />those used in the corresponding corrected effective model. Along the Cache la Poudre River <br />main chmmel the 1994 Mmming's n values were adopted for the existing condition analysis. <br />Along the LINC DFP where cross sections intercepted buildings; the buildings were coded <br />directly into the cross section's geometry. Therefore, LINC DFP Mmming's n values were 0.035 <br />except where streets were present and a 0.020 value was utilized. <br /> <br />eOFC2003-1O Oxbow FINAL LOMR.doc <br /> <br />6.1 <br /> <br />ANdERSON CONsulTiNG ENGiNEERS, INC. <br />