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FLOOD04329
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Last modified
1/25/2010 6:45:56 PM
Creation date
10/5/2006 12:33:10 AM
Metadata
Fields
Template:
Floodplain Documents
Designation Number
534
County
San Miguel
Community
Unincorporated San Miguel County
Basin
San Juan/Dolores
Title
Flood Insurance Study - San Miguel County and Incorporated Areas
Date
9/1/1992
Designation Date
11/1/2000
Floodplain - Doc Type
Floodplain Report/Masterplan
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<br />were separated at each gaging station, etatietics were developed <br />for each type of event, and the two frequency curves were <br />statistically combined (streamflow records were obtained from the <br />USGS, Denver Federal Center); (2) ehort period statistics were <br />adjusted to reflect long period values if they were closely <br />correlated; (3) outliers and historical data were considered during <br />the development of flood-flow frequency relationships for each <br />gaging station; and (4) regional relationships relating basin area <br />to peak discharge for the 10-, 50-, 100-, and SOO-year floods were <br />developed. <br /> <br />The regional relationships relating basin area to peak discharge <br />for the 10-, 50-, 100-, and SOO-year floods thus established were <br />employed to compute the peak discharges used for detailed hydraulic <br />analyses at various locations for each of these floods, and 100- <br />year peak discharges for the approzimatemethods. The r-egional <br />relationships were considered valid only for- watersheds having <br />drainage areas larger than 10 square miles, which is the lower <br />limit of the gaging stations used in regression analyses. <br />Ther-efore, for Cornet Cr-eek, which has a drainage area of 2.38 <br />squar-e miles, the SCS Curve Number technique was used to compute <br />the 100-yen flood discharge (Refer-ence 11). The 10-, 50-, and <br />SOO-year floodflows on Cornet Creek were also estimated from the <br />frequency-discharge curve drawn parallel to the curve obtained from <br />the r-egression values. <br /> <br />Peak diSCharge-drainage area relationships for each str-eam studied <br />by detailed methods in the community are shown in Table 2. <br /> <br />TABLE 2. SUMMARY OF DISCHARGES <br /> <br />Flooding Sour-ce <br />and Location <br /> <br />Drainage Ar-ea <br />(sQuare miles) <br /> <br />Peak Dischar-ges (cubic feet per second)- <br />10-Year 50-Year 100-Year- SOO-Year <br /> <br />San Miguel River- <br />Just west of <br />P1acerville 289.6 3,210 5,150 6,210 9,550 <br />Just downstream <br />of Leopar-d Greek 285.8 3,180 5,100 6,150 9,480 <br />Just upstr-eam of <br />Leopard Creek 223.4 2,660 4,320 5,250 8,220 <br />Just downstream of <br />Fall Creek 217 .8 2,610 4,240 5,160 8,100 <br />Just upstream of <br />Fall Creek 175.8 2,230 3,670 4,490 7,160 <br />Just east of Sawpit 168.6 2,160 3,570 4,370 6,990 <br />At State Highway 145 42.4 790 1,390 1,790 3,150 <br />At confluence oi <br />Eder Creek 35.37 690 1,230 1,590 2,830 <br /> <br />9 <br />
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