Table 1.
Flume test conditions.
Fig 1.
Vertical velocity profiles for each set of conditions tested in the flume.
Measurement depth is normalized by water depth and the result subtracted from 1 to obtain normalized measurement height above the bottom, and velocity is normalized by depth-averaged velocity. The point opacity is proportional to water depth, with increasing opacity corresponding to increasing water depth.
Fig 2.
Histograms of velocity ratios for each substrate.
The dashed vertical lines are the mean velocity ratio for each substrate. The solid black vertical line is the overall mean velocity ratio.
Fig 3.
Velocity ratio versus water depth for all conditions.
The horizontal dashed line shows the average velocity ratio of 0.92 for the smooth substrate; the second dashed line is the line of best fit between velocity ratio and water depth for the gravel and cobble substrates.
Table 2.
Summary of precision and bias for each alternative method.
Fig 4.
COV and SME versus water depth and depth-averaged velocity for each alternative velocity method.
Table 3.
Correlations between the performance metrics (CV and SME) and the stream variables (water depth and depth-averaged velocity) for each alternative velocity method.
Fig 5.
Surface velocity versus (uncalibrated) velocity measured with the velocity head rod method.
The colored lines are best fit lines for each substrate type and the black line is the best-fit line for all measurements.
Table 4.
T-test results for paired sets of rising body measurements.
Table 5.
Correlation coefficients of water depth and vertical velocity for rising floats filled with different volumes of water.
Fig 6.
Histogram of calculated vertical air bubble velocities.
The vertical dashed line shows the mean vertical velocity of 19.4 cm/s.
Fig 7.
Relative precision, as measured by the CV, of the four alternative velocity methods under different conditions.
Different colored circles represent different measurement techniques and the size of the circle represents the relative CV value, with larger circles showing less precision and smaller dots more. Each group of colored bubbles is centered on the coordinates representing the tested water depth and depth-averaged velocity. Individual bubbles are offset from this position, however, to avoid overlap.
Fig 8.
Accuracy, as measured by the SME, of the four alternative velocity methods under different conditions.
Each color circle represents a different measurement technique and the size of the bubble represents the relative SME value, with larger circles showing less accuracy and smaller dots more. Each group of colored bubbles is centered at the coordinates representing the depth and velocity tested, however the individual bubbles are offset from this position to avoid overlap.