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waterway on the chart ) . Therefore, the overland flow <br /> time is 210' / 3fps or 7U secands or 1. 1 minutes. <br /> Therefore� the time af concentration, or T , is 1. 1 <br /> c <br /> minutes plus an additional 10 minutes to allow for the <br /> lag between the time rainfall starts to the time runoff = <br /> 0 <br /> � <br /> .» <br /> 6egins for a total T = 11. 1 minutes. m <br /> c � <br /> ..«. <br /> � � <br /> SteP 3 Ralnfall Intensity �„� <br /> �n x <br /> From figure 2 of the handout we read an rainfall �m <br /> mR <br /> intensity, I, of 1 .75 in/hr for T = 11 min and a 10 0� <br /> c <br /> year design starm. �'� <br /> ., <br /> oz <br /> c <br /> � i <br /> .. .. <br /> Step 4 Tributary Area ��' <br /> � <br /> The tributary area of 26� IOU SF is the same as the �� <br /> -i <br /> x <br /> project area. In acres the tributary ai-ea, A� is 0.60 r+N <br /> Cm <br /> AC. S N <br /> ��1 <br /> = n <br /> �r <br /> • m <br /> a <br /> Step 5 Ratianal Formula 7O <br /> � <br /> x <br /> The allowable outflow, Q, will be datermined using the = <br /> � <br /> rational 4ormula� Q = C IA or � <br /> allow exist `� <br /> p = f0.64) (1 .75) (0.60) = 0.67 CFS = <br /> 0 <br /> � <br /> al l ow `" <br /> c� <br /> m <br /> Step 6 kequired Storage Volume <br /> The amount of storage volume required will be found be <br /> sequential use of the iollowing formulas for a 25 year <br /> design storm in accordance with the handout. <br /> Qo = Qallow T = -25 + 2706 <br /> Qo <br /> (A) (C ) <br /> dev <br />