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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 /> <br />SCS TR-55 Methodoloav <br />Q = (P-0.25)'/(P+0.85) <br />5=(1 000/CN)-1 0 <br />qp = QuAQ <br /> <br />Hvdroloav Calculations <br />Town of Granby <br />Basin B2 <br /> <br />where: <br />Q = runoff depth (inches) <br />5 = potential abstraction <br />CN = SCS Curve Number <br />A = drainage area (acres) <br />P = rainfall depth (inches) <br />Q u = Unit Peak Discharge (cfs/sm/in) <br /> <br />Catchment Data <br />Location Western Colorado (II) <br />CatchmentlD = <br />Basin Area, A = <br />NRCS Soli 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 />Pasture <br />Roads <br /> <br />Percent <br />40% <br />0% <br />55% <br />5% <br />100% <br /> <br /> <br />Storm 5 yr- 24 hr 10yr-24hr 50yr-24hr 100 yr - 24 hr <br />Potential Abstration, 5 2.26 2,26 2.28 2,26 <br />Runoff Depth, Q (Inches) 0.28 0.39 0.90 1.05 <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 />D <br />Total <br /> <br />Peak Dlscharae <br /> <br />Channel Flow <br />Too = U(I.49/n)R"" 5 1/2 <br />where: <br />R = Hydraulic Radius n = Roughness Coeff, <br />5 = Channel Slope L = Length of Flow <br />T co = Time of Concentration, Channel Flow <br /> <br /> <br />V Tcoor Tee <br />(IVs) (min) <br />0.9 6.3 <br />6.4 0.9 <br />5.6 1.5 <br />2,3 8.7 <br /> <br /> <br />8/20/02 <br />TR55-hydrology.xls <br />