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.. <br />' The overland flow method of determining time of concentration is expresaed <br />in Figure 5 -I. <br /> <br />50 .I .2 .3 .5 <br />30 <br />z <br />~ 20 <br />o: <br />W <br />o. <br />2 <br />w 10 <br />a <br />0 <br />N 5 <br />:L <br />7 <br />r 3 <br />s <br />2 <br />5 <br />.I <br />f 2 3 5 10 20 <br /> <br /> • <br /> <br /> a <br /> a o <br /> • ~. <br /> ~ <br /> <br /> : <br />a <br /> O <br /> o ,p <br /> <br /> <br /> f ~ <br /> ~ i <br /> ~ <br />: . <br /> <br />l= ~ <br />4 , <br />, <br />r <br /> 3 0 ~ . <br /> <br /> 1 40 <br /> W~ <br />t ~ <br /> 4 k~ _~ <br /> <br /> <br /> <br /> O <br /> <br />.2 .3 .5 I Z 3 5 10 <br />VELOCITY IN FEET /SECOND <br />Figure 5-I AVERAGE VELOCITIES FOR ESTIMATING TRAVEL <br />TIME FOR OVERLAND FLOW. <br />(From ~ USDA, Soil Conservation Service, 1980) <br />50 <br />30 <br />20 <br />10 <br />5 <br />3 <br />2 <br />.5 <br />20 <br />Time of concentration is obtained by determining the average velocity for <br />overland flow then dividing the length of the overland flow by the average velocity. <br /> <br />