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<br />e <br /> <br />e <br /> <br />. <br /> <br />Table 1: Watershed Summary <br /> <br /> <br />Upper Basin <br /> <br />· Large amount of storm volume <br /> <br />· Difficulty in collecting and <br />storing runoff <br /> <br />. Large peak storm flow <br /> <br />· The natural stream course is <br />to <br />interrupted by the Larimer and <br />Weld Canal <br /> <br />· Localized flooding <br /> <br />· I_ILl!.~ conveyance and an <br />(adequate oytlet for storm flows to <br />'outfall -to the Cache La Poudre <br />River <br /> <br />· Above Douglas Dam <br /> <br />Middle Basin <br /> <br />· Below Douglas Dam <br />Larimer & Weld Canal <br /> <br />Lower Basin <br /> <br />· Below Larimer & Weld Canal <br />to confluence with Cache la <br />Poudre River <br /> <br />· Dry Creek Basin channel is <br />largely obliterated <br /> <br />· Serious flooding potential <br />affecting many exiting structures <br /> <br />EXISTING BASIN STUDIES <br /> <br />Three previous hydrologic evaluations have been performed for the Dry Creek watershed: <br /> <br />Gingery Associates, Inc., (1977 and 1980) referred to herein as the GAl study. <br /> <br />Resource Consultants, Inc., 1992 referred to as RC!. <br /> <br />Lidstone and Anderson Inc. (1997), referred to as LA!. <br /> <br />The hydrologic information published in the effective Flood Insurance Study (FIS) for the <br />City of Fort Collins (March 18, 1996) indicates a peak 100- year discharge at State <br />Highway 287 as 2,900-cfs. This information is based on the GAl Study. <br /> <br />A second analysis of the watershed hydrology was conducted in October 1992 by RCI <br />under contact to the Omaha District, of the US Army Corps of Engineers. The hydrologic <br />information contained in that report indicates much higher 100-year peak discharge <br />(approximately 5,022-cfs upstream of the L-W Canal). <br /> <br />The City of Fort Collins contracted an independent review of the RCI hydrology by LAI <br />to verify the information contained in the RCI Study. The results indicated similar peak <br />100-year discharges (approximately 5,600-cfs at the L-W Canal). The current study uses <br />the existing HEC-1 model developed by ReI for the US Army Corps of Engineers and new <br />rainfall intensities to determine and compare the effectiveness of alternative flood control <br />measures. <br /> <br />14 <br />