Laserfiche WebLink
B <br />0.30 <br />Q A Soil Dev.Tc I Fm Q Notes <br />(acres) type type (min) (in/hr) (in/hr) (cfs) <br />Q10 0.053 B Res. 5.7 3.77 0.14 0.17 Initial <br />area <br />Q25 0.053 B Res. 5.7 4.48 0.14 0.21 Initial <br />area <br />Q100 0.053 B Res. 5.7 5.74 0.14 0.27 Initial <br />area <br />ap <br />% <br />Soil group <br />FP= <br />Pervious <br />sq-ft sq-ft <br />2,328.0A 0.452 <br />Area <br />A <br />RUNOFF CALCULATIONS <br /> Section II: Post – Construction Hydrology Calculations <br />RATIONAL METHOD HYDROLOGY CALCULATIONS <br />Project location: 317 N Maxine St., UNIT 2 Santa Ana, CA 92703 <br />The Rational method is commonly used for determining peak discharge from relatively small drainage <br />area. The Rational method is based on the following equation: Q = 0.9(I - Fm)A <br />Where: Q = peak discharge, in cubic feet per second (cfs) <br />Fm = ap x Fp : maximum loss rate (in/hr) <br /> Fp = Loss rate for soil group B (in/hr) from O.C. Hydrology manual. <br /> ap = Pervious area percentage: <br /> ai = Impervious area percentage <br />I = a x tb = average rainfall intensity for a duration equal to the Tc for the area (in/hr) <br /> a & b: factors in the Intensity regression equation from the Orange County Hydrology Manual <br /> t = time of concentration (min.) <br />A = drainage area contributing to the design location, in acres. <br />15.560 -0.573 <br />Factors in the Intensity regression equation from the <br />Orange County Hydrology Manual <br />For 10-year storm <br />For 25-year storm <br /> For 100-year storm <br />a b <br />10.209 -0.573 <br />11.995 -0.566 <br />Area <br />1,052.0 <br />Page 4 of 8