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<br /> <br />. '. <br /> <br />measured by planimetry. Accumulative distance upstream fro~ the <br /> <br />outlet was plotted versus respective accumulative area. <br /> <br />2. An average flow velocity, v, in miles per hour, was estimated <br /> <br />for each subarea, Values selected for each subarea are listed in <br /> <br />attached Table A-2. These selections were made by judgment <br /> <br />consideration of the following items: <br /> <br />a. An average velocity of 3.0 miles per hour was obtained <br /> <br /> <br />from an analysis of the May 6-7, 1969 rain and flood <br /> <br /> <br />runoff for subarea C-13. <br /> <br /> <br />b. Velocities'obtained from computations for Tc by the <br /> <br />equation from California Culverts Practice given on <br /> <br /> <br />page 71, Design of Small Dams, 2d Edition. <br /> <br /> <br />c. Field observations from the air and on-the-groundinspectior& <br /> <br />3.' A travel time, T in hours, was computed for each subarea by <br /> <br />dividing the total basin length in miles by respective average <br /> <br />velocity in miles per hour. <br /> <br />4. The computational procedure evaluates attenuation effect by <br /> <br />expressing it in ~~urs as a factor.R to be substituted in the <br /> <br />equation for computing the routing constant K. Our experience has <br /> <br />shown that R can be computed as O.ST for natural watersheds which <br /> <br /> <br />have efficient drainage patterns and normal channel storage. R <br /> <br /> <br />may be increased for watersheds'with poor drainage systems or <br /> <br />12 <br /> <br />""''':'~ .......-....J..............- .~__.,............'"'~'~~I. ...... <br /> <br />.'l~ _ <br /> <br />~. <br /> <br />'.... <br /> <br />. <br />