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. SYLLABUS . The purpose of this reconnaissance study is to evaluate flood problems along Boxelder, Spring, and Dry Creeks in the Fort Collins, Colorado, area. Several previous studies of the flood problems on Boxelder, Spring. and Dry Creek5 bave been completed which had an effect on the scope of this study. The selected plan would divert Dry Creek flows from about 500 feet upstream from Larimer and Weld Canal to tbe Cache La Poudre River. This channel diversion would be about 5,600 feel in length. The plan would reduce the EAD on Dry Creek from $658,700 to $288,500, or a reduction of 56 percent. The estimated construction cost of the 3D-year plan is $3,498,500. The plan would bave annual net benefits of $64,600, annual costs of $315,100, and a benefit-cost ratio of 1.2. Studies conducted by tbe City of Fort Collins on Boxelder Creek in tlJe early 1980's indicated that structural measures would be infeasible. A review of tlJose studies and the limited changes in flood plain development since that time indicate that funher studies of the flood problems on Boxelder Creek are Dot warranted. Although the recommended 3()..year level of protection channel diversion does provide considerable benefits to the Dry Creek area, it does not fulfill the City's desired goal of removing the flood hazard and flood plain restrictions along Dry Creek. The l00.year level of pr~tection cbannel diversion could be implemented; however, as the study stands now, the sponsor would be required to pay all costs above tlle cost of the National Economic Development plan (the 3o.year level of protection plan). Studies conducted on Spring Creek in 1988 by the City of Fon CoUins indicate that flood control measures would be feasible in some reaches of Spring O:cek. The City completed construction of flood cuntrol measures on Spring Creek between College Avenue and the Burlington Northern Railroad in 1990 and furtber flood control improvemcnts are planned for completion within 2 to 3 years. Flood control measures on remaining portion.> of Spring Creek do not appear to be cconomically feasible. The new hydrology prepared for this reconnaissance study is a coucern of the City of Fon Collins and Larimer County because it increases tbe project costs comiderably. The Cnrps of Eugineers met with tbe City of Fort Collins, larlmer County, and the Colorado Water Conservation Board on May 6, 1993, to discuss tbese concerns and to provide supporting information concerning tbe differences. Al'lclitional hydroJogystudies can be pursued during the cost-shared feasi bilitystudy to further eJlplore sensitive hydrologypararnetcrs and alternatives tha t may result in more cost cffective projeets, or which rnayincrease tbe level of protection oftbe NP....D plan for Dry Creek. Average annual damages on Dry Creek are estimated to be $658,700. It would be economically feasible to construct flood control measures on Dry Creek in the northwest portion of Fort Collins. A 30-year level of prolo:oction channel diversion was selected as the reconnaissance-le.'el plan A tOO-year level of protection channel diversion would not be feasible. Corps interest does ex.isl in more detailed cost-shared studies leading towards a possible flood damage reduction plan. . .