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<br />Catchment Data <br />Location I Western Colorado (II) <br />Catchment ID = <br />Basin Area, A = <br />NRCS Soil Type = <br />Overland Flow Type I Short Grass Pasture & Lawns' <br />Runoff Depths <br />Storm <br />Rainfall Frequency (years) <br />Rainfall Duration (hours) <br />Rainfall Depth, P (inches) <br /> <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />... <br /> <br />SCS TR-55 Methodoloav <br />Q = (P-0,2S)'/(P+0.8S) <br />S=(1000/CN)-10 <br />qp = Q,AQ <br /> <br />Weighted Curve Numbers, CN <br />Sub-Area <br />1 <br />2 <br />3 <br />4 <br />Sum <br /> <br />Total Runoff <br /> <br />Hvdroloav Calculations <br />Town of Granby <br />Basin A2 <br /> <br />where: <br />Q = runoff depth (inches) <br />S = potential abstraction <br />CN = SCS Curve Number <br />A = drainage area (acres) <br />P = rainfall depth (inches) <br />Q, = Unit Peak Discharge (cfs/sm/in) <br /> <br />~ <br />i.;~ <br />{ ~4~aJ acres <br />kt.:...::.'C:Of.. <br />ijf, > ^ -Ii<'! <br />~~ <br /> <br /> <br />Descri tion <br />Residential <br />Commercial <br />Pasture <br />Roads <br /> <br />Percent <br />1% <br />0% <br />98% <br />1% <br />100% <br /> <br /> <br />Storm 5yr-24hr 10vr - 24 hr 50yr-24hr 100 yr - 24 hr <br />Potential Abstration, S 2.62 2.62 2.62 2.62 <br />Runoff Depth, Q (inches) 0.22 0.31 0.78 0.92 <br /> <br />Time of Concentration <br />Overland Flow <br />From Figure 3-1, TR-55 <br /> <br />BasIn Calculallon <br /> <br />Reach <br />A <br />B <br />C <br />D <br />Total <br /> <br />Peak Dlscharae <br /> <br />Flow <br />Tye <br />overland' <br />ch.annel <br />channel <br /> <br />Channel Flow <br />T ~ = L/(1.49/n)R2J3 S 112 <br /> <br />where: <br />R = Hydraulic Radius n = Roughness Coeff. <br />S = Channel Slope L = Length of Flow <br />T co = Time of Concentration, Channel Flow <br /> <br />L <br />(feet) <br />"450' . <br />'.'20P' <br />.,22Q!l.' <br /> <br /> <br />V Teoor Tee <br />(ltIs) (min) <br />0.5 16.5 <br />0.8 4.0 <br />0.9 40.0 <br />0.8 60.5 <br /> <br />n <br /> <br />. 10:030' <br /> <br />H'> <br /> <br />2850 <br /> <br /> <br />Unit Peak Discharge (cfs/sm/lnch) <br />Area sm <br />IlifJUf S!!I!' rgo: dJs <br /> <br />8/20/02 <br />TR55-hydrology.xls <br /> <br />