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Table <br />GUIDE FOR THE DETERMINATION OF RUNOFF COEFFICIENTS <br />FOR BUILT -UP AREAS* <br />WATERSHED <br />8 -11% <br />12 -15% <br />1.0 <br />CHARACTERISTICS <br />EXTREME <br />HIGH <br />MODERATE <br />LOW <br />INFILTRATION <br />NEGLIGIBLE <br />SLOW <br />MEDIUM <br />HIGH <br />6.0 <br />0.20 <br />0.14 <br />0.07 <br />0.0 <br />STEEP <br />HILLY <br />ROLLING <br />FLAT <br />RELIEF <br />(�-25 %) <br />(15 -25 %) <br />(5 -15 %) <br />(0 -5 %) <br />0.08 <br />0.06 <br />0.03 <br />0.0 <br />VEGETAL <br />NONE <br />POOR <br />GOOD <br />HIGH <br />(< 10 %) <br />(10- 500/6) <br />(50 -90%) <br />COVER <br />0.07 <br />0.05 <br />0.03 <br />0.0 <br />INDUSTRIAL <br />HOTEL - <br />DEVELOPMENT <br />a BUSINESS <br />APARTMENT <br />RESIDENTIAL <br />AGRICULTURAL <br />TYPE <br />0.55 <br />0.45 <br />0.40 <br />0.15 <br />i ire ur�igi, t 111[7e77t c must result prom a total 01 the values for all four <br />watershed characteristics of the site. <br />APPROXIMATE AVERAGE VELOCITIES OF RUNOFF <br />FOR CALCULATING TIME OF CONCENTRATION <br />TYPE OF FLOW <br />OVERLAND FLOW: <br />Woodlands <br />Pastures <br />Cultivated <br />Pavements <br />OPEN CHANNEL FLOW: <br />Improved Channels <br />Natural Channel* <br />(not well defined) <br />VELOCITY IN FPS FOR SLOPES <br />(in percent) INDICATED <br />0 -3% <br />4 -7% <br />8 -11% <br />12 -15% <br />1.0 <br />2.0 <br />3.0 <br />3.5 <br />1.5 <br />3.0 <br />4.0 <br />4.5 <br />2.0 <br />4.0 <br />5.0 <br />6.0 <br />5.0 <br />12.0 <br />15.0 <br />18.0 <br />Determine Velocity by Manning's Formula <br />1.0 3.0 5.0 8.0 <br />*These values vary with the channel size and other conditions <br />so that the ones given are the averages of a wide range. Where. <br />ever possible, more accurate determinations should be made for <br />particular conditions by Manning's formula. <br />14 <br />1 <br />Table 2 <br />