FLOOD01191

• County: Statewide
• Title: Laboratory Data on Course-Sediment Transport for Bedload-Sampler Calibrations
• Date: 1/1/1987
• Prepared By: USGS
• Floodplain - Doc Type: Educational/Technical/Reference Information

0.62

0.60

w 058
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f- 0.56
c...
w
U
0::
W
f- 0.54
Z

0.52

0.50
1.4

1.5

1.6

1.8

1.9

1.7

HEIGHT OF BED ABOVE FLOOR, IN FEET

Figure 22. Variation of intercept values of CcrhlW relalions with heighl of the bed surface above the flume floor. C", dimensionless
weir discharge coefficient; h, head on the weir; W, height of the weir crest above the channel bottom.

Water-surface elevations are available on magnetic
media (see Availability of Data, inside back cover) in the
files named in column 6 of table 7. The elevation datum is
Ihe horizontal flume floor.

Longitudinal Streambed-Surface Elevation

Streambed-surface elevations along the channel were
measured periodically during each run by means of an ultra.
sonic sounder (fathometer) capable of measuring dislance 10
the nearest 0.01 ft. The sounder's voltage output, which is
proportional to the distance between the transducer face and
the bed, was graphed on a strip-chart recorder. The Irans-
ducer probe was mounted on the mobile measurement cart
(fig. lOBi at a lateral position coincident with the centerline
of the channel; the transducer was submerged about 15 in.
The cart traversed the length of the channel along horizontal
sleel rails. One wheel of the cart was constructed with a
milled recess at the outside. A microswitch contact mounted
on the cart was actuated with every revolution of the wheel.
Each switch closure produced a tick mark on the graphic

recorder indicative of 0.4713 ft of travel. Longitudinal pro.
files of the streambed-surface elevation were obtained by
moving the measurement cart to the upstream end of the
channel and then manually pushing the unit slowly down-
stream while the sounder produced a continuous graphic
record of depth below the transducer face and the progres-
sion of tick marks delineated horizontal distance. The
sounder was calibrated at the beginning and end of most
days to define slight shifts in the parameters of the linear
relation between voltage and distance.
The graphic records of all profiles were digitized and
then converted by using calibration curves to provide values
of actual distance between the transducer face and the
streambed at intervals of about 0.15 ft along the measured
reach. The exact lengths of the intervals varied, depending
on the recorder chart speed and the rate of movement of the
cart, because digitized values were automatically read every
0.03 in. along the graphic record. The variable-interval
data, in turn, were converted by interpolation between the
distance marks to transducer-to-streambed distances every
0.2 ft along the measurement reach. Because the transducer

22 Laboratory Data on Coarse-Sediment Transport for Bedload-Sampler Calibrations