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<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+O.8S) <br />S=(1000/CN)-10 <br />qp = Q,AQ <br /> <br />HvdroloGv Calculations <br />Town of Granby <br />Basin B3 <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 (cls/sm/in) <br /> <br />Catchment Data <br />Location Western Colorado (II) <br />Catchment ID = <br />Basin Area, A = <br />NRCS Soil Type = <br />Overland Flow Type <br />Runoff Depths <br />Storm <br />Rainfall Frequency (years) <br />Rainfall Duration (hours) <br />Rainfall Depth, P (inches) <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 /> <br />Description <br />Residential <br />Commercial <br />Open space <br />Roads <br /> <br /> <br />Percent <br />70% <br />15% <br />10% <br />5% <br />100% <br /> <br />Storm 5yr-24hr 10yr - 24 hr 50yr - 24 hr 100 yr - 24 hr <br />Potential Abstration, S 1.95 1.95 1.95 1.95 <br />Runoff Depth, Q (inches) 0.35 0.46 1.02 1.18 <br /> <br />Time of Concentration <br />Overland Flow <br />From Figure 3-1, TR-55 <br /> <br />Basin Calculation <br /> <br />Reach <br />A <br />B <br />C <br />o <br />Total <br /> <br />Peak Dlscharae <br /> <br />Channel Flow <br />T" = U(I.49/n)R2/3 S 1/2 <br />where: <br />R = Hydrauiic Radius n = Roughness Coeff. <br />S = Channel Slope L = Length of Flow <br />T co = Time of Concentration, Channel Flow <br /> <br /> <br />V Teoor Tee <br />(ftIs) (min) <br />1.1 7.6 <br />3.9 8.3 <br />4.1 2.9 <br />2.8 18.7 <br /> <br /> <br />8/20/02 <br />TR55-hydrology,xls <br />