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<br />Photographs were taken depicting the flow conditions during each measure- <br />ment session. The water-surface slope at each site was measured during two of <br />the site visits. Bed-material data were collected during low-flow conditions. <br /> <br />Velocity Measurement <br /> <br />Measurements of velocity in streams most often are done to determine <br />stream discharge. As noted in the Introduction of this report, the usual <br />method for computing discharge is to sum the products of the subsectional mean <br />velocities and the corresponding subsectional areas (Rantz and others, 1982). <br />Methods for determining the subsectional mean velocity from pOint-velocity <br />measurements are discussed briefly in the section "Mean Velocity". Point <br />velocities normally are measured by use of a current meter. Two types of <br />current meters, a standard Price type AA current meter and a prototype Price <br />Model PAA current meter, were used in this study. <br /> <br />The Price type AA current meter (fig. 3) was used because it is the <br />principal velocity measuring device used by the Survey (Rantz and others, <br />1982). Problems have been identified with using the Price type AA current <br />meter where the velocities in the vertical are abnormally distributed by <br />submerged objects such as large bed material (Rantz and others, 1982). The <br />Price type AA current meter registers vertical-velocity components under the <br />turbulent conditions that often exist in high-gradient streams (Townsend and <br />Blust, 1960; Linsley and others, 1982, p. 104). Hence, recorded velocity is <br />greater than the actual longitudinal velocity. Velocity-profile data were <br />collected at two streams, sites 4 and 5, to evaluate the magnitude of the <br />effects of turbulence on low-gradient streams. <br /> <br /> <br />Figure 3.--Price type AA current meter. <br /> <br />7 <br />