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FLOOD04880
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Last modified
1/25/2010 6:47:35 PM
Creation date
10/5/2006 1:06:44 AM
Metadata
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Template:
Floodplain Documents
Designation Number
372
County
Boulder
Community
Superior
Basin
South Platte
Title
Flood Insurance Study - Superior, CO, Boulder County
Date
3/1/1979
Designation Date
9/1/1994
Floodplain - Doc Type
Floodplain Report/Masterplan
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<br />In May 1969, damage to land irrigation structures and agriculturE <br />totalled approximately $75,000. <br /> <br />2.4 Flood Protection Measures <br /> <br />No flood protection structures either ekist or are planned within <br />and adjacent to the Town of Superior. <br /> <br />~ <br /> <br />3.0 ENGINEERING METHODS <br /> <br />. <br /> <br />For the flooding sources studied in detail in the community, standard <br />hydrologic and hydraulic study methods were used to determine the flood <br />hazard data required for this study. Flood events of a magnitude which <br />are expected to be equalled or exceeded once on the average during any <br />10-, 50-, 100-, or SOC-year period (recu~ce interval) have been selected <br />as having special significance for flood plain management and for flood <br />insurance premium rates. These events, commonly termed the 10-, 50-, <br />100-, and SOD-year floods, have a 10, 2, 1, and 0.2 percent chance, <br />respectively, of being equalled or exceeded during any year. Although <br />the recurrence interval represents the long term average period between <br />floods of a specific magnitude, rare floods could occur at short intervals <br />or even within the same year. The risk of experiencing a rare flood <br />increases when periods greater than 1 year are considereo. For example, <br />the risk of having a flood which equals or exceeds the 100-year flood <br />(1 percent chance of annual occurrence) in any 50-year period is approxi- <br />mately 40 percent (4 in 10), and, for any 90-year period, the risk increases <br />to approximately 60 percent (6 in 10). The analyses reported here reflect <br />flooding potentials based On conditions existing in the community at the <br />time of completion of this study, Maps and flood elevations will be <br />amended periodically to reflect future chanqes, <br /> <br /> <br />3.1 Hydrologic Analyses <br /> <br />Hydrologic analyses were carried out to establish the peak discharge- <br />frequency relationships for floods of the selected recurrence <br />intervals for each stream studied in detail in the community. <br /> <br />There are no stream gages on Coal Creek for determining discharge <br />measurements. <br /> <br />This report is based on the data generated for the October 1976 <br />study of Coal Creek and Rock Creek performed by the u.S. Soil Con- <br />servation Service (Reference 2). Because no streamflow records <br />exist for Coal Creek, the u.s. Soil Conservation Service used the <br />synthetic hydrograph method to determine flows for storms of various <br />frequencies. Analyses were based on a storm duration of 24 hours, <br />Type 11, and IIA distribution, as described in the u.S. Soil Conser- <br />vation Service National Enqineerinq Handbook, Section 4 (Reference <br />3). The amount of rainfall was obtained from a precipitation fre- <br />quency atlas (Reference 4) and areal adjustment was applied to <br /> <br />5 <br />
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