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<br />. <br /> <br />3.2 COFC Analyses <br /> <br />Due to the extensive flooding, damage, and loss of life that occurred during the Spring <br />Creek Flood of 1997, the City of Fort Collins reviewed its floodplain regulations for the Cache la <br />Poudn~ River. In the interest of public safety and reducing the potential for property damage <br />along the Cache la Pouter River corridor, the COFC adopted a tenth-foot rise floodway and a <br />product 6 corridor on the Cache la Poudre River in 2000. A floodway is the chmmel of a river or <br />other watercourse and the adjacent land areas that must be reserved in order to discharge the base <br />flood (i.e. 100-year flood) without cumulatively increasing the water surface elevation by more <br />than a specified depth (i.e. tenth-foot). <br />Per City of Fort Collins regulations, the product 6 corridor is defined as the chmmel of a <br />waten:ourse or other area of potential flooding, the boundaries of which are defined by the depth <br />of water, measured in feet, multiplied by the velocity of the water, measured in feet per second, <br />for a 500-year flood such that the product is greater than or equal to 6. <br />The original effective tenth-foot rise floodway and product 6 corridor hydraulic models <br />were developed by Ayres Associates, Inc. [Ayres 2000]. As a result of changes to the main <br />chmmel geometry during the 2005 Removal Action Project the original 2000 COFC models were <br />updated in the 2005 Removal Action LOMR. The 2005 Removal Action LOMR COFC models <br />were considered the effective models for the current study and were obtained from ACE's 2005 <br />Removal Action LOMR report [ACE 2005, Revised 2006]. <br /> <br />. <br /> <br />3.2.1 Definition of Hydraulic Model/Modeling Reaches <br /> <br />The original 2000 tenth-foot rise floodway and product 6 corridor hydraulic models were <br />developed from the 1994 effective models for the Upper and Lower Reaches of the: Cache la <br />Poudre River with the following physical changes included in the models: (a) Timberline Road <br />and Bridge improvements that were documented in the 1999 LOMR; (b) drop structur,e and boat <br />chute improvements located between U.S. Highway 287 ,and the RN.R.R. that were ultimately <br />documented in the 2001 LOMR; and (c) the replacement of the U.S. Highway 287 Bridge by <br />CDOT in 1993. The U.S. 287 Bridge replacement was modeled during the 2000 analyses <br />utilizing design plans and not as-built information. It should be noted that the COFC does not <br />have a LINC DFP model separate from the FEMA model. The updated 2005 Removal Action <br />LOMR COFC models included improvements associated with chmmel work performed between <br />Linden Street and the B.N.R.R. Bridge. Table 3.3 describes the original effective and the 2005 <br />Removal Action LOMR COFC models. The 2005 Removal Action LOMR models were <br />considered effective for the current study. <br /> <br />. <br /> <br />COFC2003-1O Oxbow FINAL LOMR.doc <br /> <br />3.7 <br /> <br />ANdERSON CONsulTiNG ENGiNEERS, INC. <br />