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<br />I <br />I <br />I I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />HYDROLOGIC ANALYSIS <br />!ffiJOR DRAINAGEWAY PLANNING <br />DRY CREEK <br /> <br />- STUDY SCOPE - <br /> <br />This hydrologic analysis was prepared as part of the Master <br />Drainageway Planning Study for Dry Creek in Fort Collins and Lari- <br />mer County, Colorado. This analysis was completed according to <br />the "Scope of Work" entitled "Feasibility Study for a Flood Control <br />and Drainage Plan for Dry Creek, Fort Collins, Larimer County, <br />Colorado" (Reference 1). <br />This scope of work requires an analysis to "determine runoff <br />rates and volumes for the 2-, 5-, 10-, 50-, 100-, and SOO-year flood <br />frequencies for selected basin conditions using basin growth pro- <br />jections from planning and zoning maps of local governments." The <br />hydrology determined in this study will be used to develop a flood- <br />plain analysis which in turn will be used in developing depth-damage <br />curves for the study reach. These depth-damage curves will serve as <br />the basis for evaluating the benefit-cost information for proposed <br />improvements. <br />The intent of the Major Drainageway Planning Study for Dry <br />Creek is to identify the most cost beneficial solution to Flood Con- <br />trol and Drainage Improvements on Dry Creek. For projects such as <br />this, where the possibility of large capital expenditure for an im- <br />provement system exists, a detailed hydrologic study is warranted, <br />particularly considering the complexities of the Dry Creek Basin. <br />The Surface Water Management Model (SWMM) (Reference 2) was <br />selected for use in this study and was approved for use by the <br />Technical Committee at our initial meeting. This hydrologic model <br />is a very detailed kinematic wave model that requires the basin be <br />divided into very small increments so that the impact of each of these <br />areas can be carefully analyzed. The model accounts for channel and <br />overbank storage, lagging and combining of hydrographs, and reservoir <br />routing. The model can be easily altered to look at varying basin <br />conditions and will be available to the City and County to evaluate <br />the impact of future development projects within the basin. <br /> <br />-1- <br />