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<br />VERTICAL-VELOCITY DISTRIBUTION <br /> <br />The vertical-velocity distribution in fully developed turbulent <br /> <br />flow has been shown to be approximately logarithmic (Chow, 1959). <br />~ <br />Studies (Hulsing and~, 1966; Savine and Bodhaine, 1971) have ver- <br /> <br />ified the logarithmic velocity distribution of natural-flow streams. <br /> <br />fiG. q <br />~ <br />1JtW lMnI <br /> <br />The logarithmic vertical-velocity distribution for a stream is shown <br /> <br />graphically in figure 9. Measurements of streamflow velocity are <br /> <br />normally made by using a current meter to measure the velocity of water <br /> <br />flowing through incremental subareas of a channel cross section. The <br /> <br />mean velocity of the flow through each subarea is obtained by measuring <br /> <br />the velocity with a current meter at 0.6 of the depth of flow (VO.6) if <br />the depth is less than 2.5 ft (0.76 .m), or by measuring the velocities <br /> <br />at the 0.2 and 0.8 depths and averaging the results (VO.2+0.8) if the <br /> <br />depth of flow is equal to or greater than 2.5 ft (0.76) (Buchanan and <br /> <br />if <br /> <br /> <br />Somers, 1969). For example, the 0.6 distance below the water surface <br /> <br />corresponds to the mean velocity in the logarithmic vertical-velocity <br /> <br />distribution shown in figure 9. The discharge at the cross section is <br /> <br />computed using the continuity equation (equation 2). I <br /> <br />