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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />were applied to the IS-minute most intense <br />on Area-Depth Curves developed by NOAA. <br />storms used for hydrologic modelling which <br />adjustments. <br /> <br />peri od <br />Table <br />do not <br /> <br />of the design storms based <br />IV-1 shows typical design <br />include the areal rainfall <br /> <br />TABLE IV-l <br /> <br />TYPICAL 2-HOUR DESIGN STORMS <br />GOLDEN, COLORADO AREA <br /> <br />Depression and detention storage values were obtained from the Urban Drainage <br />and Flood Control District Urban Storm Drainage Criteria Manual. Values of <br />pervious and impervious detention varied from 0.3" to 0.4", and from 0.05" to <br />0.1" respectively. Infiltration loss rates were estimated based on a prelimi- <br />nary inventory of soils prepared by the U.S.D.A. Soil Conservation Service. <br />Infiltration losses were based on Horton's Equation using the following <br />infiltration values and decay rate: <br /> <br />RAINFALL (INCHES) <br /> <br />f. = 3.0 <br />1 <br /> <br />fo = 0.5 <br /> <br />0< = 0.0018 <br /> <br />(mi n) <br />Time 2-year 5-year 10-year 50-year 100-year <br />- <br />5 .02 .03 .03 .03 .03 <br />10 .04 .05 .06 .08 .08 <br />15 .08 .12 .14 .12 .12 <br />20 .16 .21 .26 .19 .21 <br />25 .25 .35 .42 .35 .36 <br />30 .14 .18 .20 .59 .65 <br />35 .06 .08 .10 .28 .36 <br />40 .05 .06 .07 .19 .21 <br />45 .03 .05 .06 .12 .16 <br />50 .03 .05 .05 .12 .13 <br />55 .03 .04 .05 .08 .10 <br />60 .03 .04 .05 .08 .10 <br />65 .03 .04 .05 .08 .10 <br />70 .02 .04 .05 .06 .05 <br />75 .02 .04 .05 .06 .05 <br />80 .02 .03 .04 .04 .03 <br />85 .02 .03 .03 .04 .03 <br />90 .02 .03 .03 .03 .03 <br />95 .02 .03 .03 .03 .03 <br />100 .02 .02 .03 .03 .03 <br />105 .02 .02 .03 .03 .03 <br />llO .02 .02 .03 .03 .03 <br />115 .01 .02 .03 .03 .03 <br />120 .01 .02 .02 .03 .03 <br />Totals 1.15" 1.60" 1. 91" 2.72" 2.98" IV-2 <br /> <br />Horton's Equation: <br /> <br />f = f + (f. - f ) e- o<t <br />010 <br /> <br />in which, <br /> <br />f = infiltration rates in inches/hour <br />f. = initi al infiltration rate in inches/hour <br />1 <br />fo = final i nfil t rat i on rates in inches/hour <br />0<- = decay coefficient in per second units <br />t = time in seconds <br /> <br />Methodology <br /> <br />- Tucker Gulch - <br /> <br />The hydrologic analysis for Tucker Gulch involved dividing the major basin <br />into five sub-basins and utilizing the Colorado Urban Hydrograph Procedure <br />(CUHP) to determi ne runoff hydrographs from each sub-bas in. The hydrographs <br />were combi ned and routed through st ream channels usi ng the Convex Rout i ng <br />Method (Ref. 13). The peak discharges of the resulting flood hydrographs were <br />used for the hydraulic modeling. <br />