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<br />I <br />I <br />I <br />I <br />I <br /> <br />SECTION I <br /> <br />4. "Flood Information <br />Reportll <br /> <br />INTRODUCTION AND SUMMARY <br /> <br />BACKGROUND <br /> <br />5. Reconnaissance <br />Report "St. Vrain <br />Unit, Coloradoll <br /> <br />Since 1864, The City of Boulder has experienced five major flood events <br /> <br />6 . Flood PIa i n <br />I nformat i on <br />Report <br /> <br />on Boulder Creek ranging in estimated discharge from 2,500 cubic feet <br /> <br />per second (c.f.s.) to 13,000 c.f.s. resulting in light to severe property <br /> <br />7. Master Plan for <br />Boulder Creek - <br />24th to 30th St. <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />damage. Al I floods for which dates are known occurred in Mayor June. <br /> <br />The flood of June 1894, the greatest flood of record at Boulder, had an <br /> <br />8. Reconnaissance <br />Report <br /> <br />estimated peak discharge of 13,000 c.f.s. The exceedence intervals of <br /> <br />these five major floods range between 10 years to lOO years as deter- <br /> <br />9. Conceptual Plan <br />for Boulder Creek <br /> <br />mined by discharge probability curves prepared by the U.S. Army Corps of <br /> <br />Engineers (COE). The flood capacity of existing Boulder Creek through <br /> <br />10. General Design <br />Memorandum <br /> <br />the City of Boulder is approximately 4,000 c.f.s. corresponding to an <br /> <br />exceedence interval of 25 years. <br /> <br />11. Env i ronmenta 1 <br />Analysis <br /> <br />Past floods on Boulder Creek have elicited sixteen previous studies <br /> <br />12. Special Flood <br />Hazard Information <br />Report <br /> <br />related to delineating and mitigating flood hazards associated with <br /> <br />Boulder Creek. These studies have been performed by various organizations <br /> <br />1 3. "11 Po in t Flood <br />Control Plan" <br /> <br />I <br /> <br />as summarized below: <br /> <br />TABLE I. I SUMMARY OF PREVIOUS STUDIES <br /> <br />14. Floodway Maps <br /> <br />I <br /> <br />RESPONSIBLE <br /> <br />REPORT NAME <br /> <br />ENTITY <br /> <br />YEAR <br /> <br />CONTENT <br /> <br />US Geological <br />Survey (USGS) <br /> <br />US Bureau of <br />Rec 1 ama t ion (USBR) <br /> <br />COE <br /> <br />Wright-McLaughlin <br />Engineers, <br />Denver, Colorado <br />(W/Mc) <br /> <br />COE <br /> <br />W/Mc <br /> <br />COE <br /> <br />Thorne Ecological <br />I nst. <br /> <br />COE <br /> <br />Corps of Engineers <br />Committee on <br />Env i ronmen ta 1 <br />Planning <br /> <br />Frazier & Gingery <br />Eng i neers, Denver, <br />Colorado <br /> <br />I <br />I <br /> <br />15. Met ropo 1 i tan Denver COE <br /> & South Platte River <br /> ,. Tributaries Study <br />16. Pub 1 i c I nformat ion COE <br /> Fact Sheet <br /> <br />1. <br /> <br />II ThE.. Imp rovenien t of <br />of Boulder Creekll <br /> <br />Frederick L. Olmstead 1910 <br /> <br />Land use relationship <br />with Flood Plain <br /> <br />11308" Report on <br />the Platte River <br />Basin <br /> <br />1938 <br /> <br />2. <br /> <br />COE <br /> <br />Navigation, Flood <br />Control, Power <br />Oevelopment and <br />Irrigation <br /> <br />I <br />I <br />I <br /> <br />1945 <br /> <br />3. <br /> <br />South Platte River <br />and Tributaries, <br />Colorado, Wyoming, <br />and Nebraska <br /> <br />COE <br /> <br />Flood Protection <br />on Boulder Creek <br />and Sunshine Creek <br /> <br />1961 <br /> <br />1967 <br /> <br />1969 <br /> <br />1969 <br /> <br />1970 <br /> <br />1970 <br /> <br />1971 <br /> <br />1972 <br /> <br />1972 <br /> <br />1973 <br /> <br />1974 <br /> <br />1977 <br /> <br />1977 <br /> <br />Flood-frequency <br />information upstream <br />from 28th Street <br /> <br />Damsite investigation <br />on Bou 1 der Creek <br /> <br />Flood Plain Analysis <br />based on 7400 c.f.s. <br /> <br />Proposed improvements <br />to 24th, 28th & 30th <br />Sts. based on 7400 <br />c. f. s. <br /> <br />Flood Control Measures <br />for 7400 c. f. s. <br /> <br />Proposed improvements <br />from 9th to l4th based <br />on 7400 c.f.s. <br /> <br />Development of Struc- <br />tural and non-structural <br />flood control concepts <br /> <br />Environmental impact <br />analysis of COE flood <br />control concepts <br /> <br />8asis for Boulder <br />Participation in Flood <br />Insurance Program <br /> <br />Flood Control Plan <br />based on agressive land <br />use management program <br />for 7400 c.f.s. <br /> <br />Floodway maps <br />based on 7400 c.f.s. <br /> <br />Re-Analysis of Boulder <br />Creek hydrology increasing <br />100-year flood discharge <br />to 12,000 c.f.s. <br /> <br />Development of Flood <br />Control Plans for 12000 cfs <br />1 - enlarged Channel II - <br />Excavated Floodway <br />II I - Relocation and <br />Alert Proof i ng <br /> <br />1 <br />