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FLOOD00308
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Last modified
3/31/2014 9:15:23 AM
Creation date
10/4/2006 9:11:53 PM
Metadata
Fields
Template:
Floodplain Documents
County
Larimer
Community
Fort Collins
Title
Feasibilty Study for the Dry Creek Basin Flood Control Project
Date
9/1/2001
Prepared For
Larimer County
Prepared By
ECI a Division of DMJM+Harris
Contract/PO #
FS0044FX
Floodplain - Doc Type
Floodplain Report/Masterplan
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<br />e <br /> <br />PROJECT INTRODUCTION <br /> <br />e <br /> <br />The Dry Creek watershed drains approximately 62 square miles gencrally trending north <br />to south. The headwaters are just south of the Wyoming and Colorado state line. The <br />confluence of Dry Creek and the Poudre River is the southern terminus of the watershed. <br />The confluence location is just south of the Fort Collins Airpark, in Larimer County, just <br />east of Fort Collins, Colorado, see Figure 1. <br /> <br />The watershed is approximately 23 miles long and 3 to 3.5 miles wide. The watershed is <br />mainly rural agriculture and upland dry prairie with its southern portions in rapid <br />transition to urbanized and suburbanized land uses in the northern portions of the City and <br />immediately outside the City in the County. In the late 1800's irrigation and water storage <br />reservoirs were constructed to suppoI't ranching and farming. <br /> <br />The watershed is broken into three sub-basins for the convenience of discussion purposes. <br />These sub-basins are also shown on Figure I. The Upper Basin lies above Douglas <br />Reservoir, the Middle Basin between Douglas Reservoir and the L- W Canal and the <br />Lower Basin constitutes the area lying downstream of the L- W Canal to the confluence of <br />Dry Creck with the Poudre River. <br /> <br />The objectivc of the Dry Creek Flood Control Projcct is to protect about 800 structures <br />located within the designated FEMA floodplain in the Lower Basin. However, the <br />alternatives outlined in this study provide benefits that accrue to the Middle Basin and to <br />the Company. Benefits in the Middle Basin dcpend on the location of the detention <br />features. <br /> <br />Dry Creek has not experienced serious flooding below the L- W Canal since the early <br />1900's. Flooding in Dry Creek was documented in 1904 and 1924. References to the flood <br />in 1924 are vague, and may have referred to a breach of the L- W Canal. At a recent open <br />house a long term resident remembered flooding on Dry Creek above the L- W Canal in <br />the early 1950's and again in the 90's. The absence of flooding may be attributed to the <br />network of irrigation canals and storage areas created by the presence of the existing <br />canals and reservoirs. It should be noted that the Dry Creek channel in the lower basin <br />has been largely obliterated due to urbanization below the L-W Canal where Dry Creek in <br />the middle basin ends. <br /> <br />We conclude that the potential for breaching of the irrigation canals and reservoirs during <br />floods, may considerably worsen downstream flooding during an extreme rainfall event. <br />In July 1997 a very high intensity, prolonged rainfall event struck the Spring Creek basin, <br />in southwest Fort Collins and caused considerable damage and flooding. The Spring <br />Creek is south of the Dry Creek basin. That event was 10.5 inches of rain in a 6-hour <br />period representing a return period of over a 500-year event. This type of event is not <br />unfamiliar along the Colorado Front Range. Other examples of similar events have taken <br />place in: <br /> <br />e <br /> <br />10 <br />
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