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<br />CALCULATION OF A PEAK RUNOFF USING RATIONAL METHOD <br /> <br />Project Title: <br />Catchment ID: <br /> <br />Kiowa Approximate Zone A Study <br /> <br />I. Catchment Hydrologic Data <br /> <br />Catchment ID : North <br />Area: 1101.00 Acres <br />Percent Imperviousness: 2.00 % <br />NRCS Soil Type: B A, B, C, or D <br />For catchments larger than 90 acres, CUHP hydrograph and routing are recommended. <br /> <br />II. Rainfall Information I (inch/hr) = C1 * P1/(C2 + Td)^C3 <br /> <br />Design Storm Return Period, Tr: <br />C1 : <br />C2: <br />C3: <br />P'I: <br /> <br />100 years <br />28.50 <br />10.00 <br />0.786 <br />4.20 inches <br /> <br />(input return period for design storm) <br />(input the value of C1) <br />(input the value of C2) <br />(input the value of C3) <br />(input one-hr precipitation-osee Sheet "Design Info") <br /> <br />III. Analysis of Flow Time (Time of Concentration) for a Catchment <br /> <br />Runoff Coefficient, C = <br />Overide Runoff Coefficient, C : <br />5-yr. Runoff Coefficient, C-5 : <br />Overide 5-yr. Runoff Coefficient, C : <br /> <br />0.36 <br /> <br />(enter an overide C value if dElsired, or leave blank to accept calculated C.) <br /> <br />0_08 <br /> <br />(enter an overide C-5 value if desired, or leave blank to accept calculated C-5.) <br />Illustration <br /> <br /> <br />FloIv Directio <br />'l( <br /> <br />Catchment <br />Boundary <br /> <br /> NRCS Land Heavy Tillage! Short ~arlY Grassed Paved Areas & <br /> Type Meadow Field Pasture! Bare Shallow Paved <br /> Lawns Ground Waterways (Sheet Flo -, <br />I Conveyance -II 2.5 II 5 II 7 I 10 15 20 <br /> <br />Calculations: <br /> <br />Reach Slope Length 5.yr NRCS Flow Flow <br />ID S L Runoff Convey- Velocity Time <br /> Coeff ance V Tf <br /> ftlfl ft C-5 fps minutes <br /> input input output input output output <br />Overland 0_0150 500 0.08 N/A 0.23 35.97 <br />1 0_0200 11,961 5.00 0.71 281.92 <br />2 <br />3 <br />4 <br />5 <br /> Sum 12,461 Computed Tc = 317.89 <br /> Regional Tc = 79.23 <br /> User-Entered Tc = 79.23 <br /> <br />IV. Peak Runoff Prediction <br />Rainfall Intensity at Computed Tc, I = <br />Rainfall Intensity at Regional Tc, I = <br />Rainfall Intensity at User-Defined Tc, I = <br /> <br />1.26 inch/hr <br />3.51 inch/hr <br />3.51 inch/hr <br /> <br />Peak Flowrate, Qp = <br />Peak Flowrate, Qp = <br />Peak Flowrate, Qp = <br /> <br />502.96 cfs <br />1398.92 cfs <br />1398.92 cfs <br /> <br />UD-RationaINorthBasin.xls, Tc and PeakQ <br /> <br />1/23/2006,3:45 PM <br />