42
ERDC/CRREL TR-02-14
Elevation measurements (NVD 29) were reported using Montana State plane
(NAD 27) coordinates. Water velocity measurements were obtained at all the
sites in the fall, but Vournas and Mattelin were excluded from the spring meas-
urements. Velocity measurements were taken at various points from a boat
anchored along the cross section alignment at water depths corresponding to 0.2
and 0.6 of the total water depth The reported location was relative to the bench-
mark pin on the right bank and assumed to be along the alignment. Using these
assumptions the X-Y coordinates of the measurement location were calculated
using linear interpolation along the alignment.
For the ice surveys, personnel from the NRSC Culbertson office used one of
the open water survey pins as a benchmark. At the Culbertson, Tveit-Johnson,
and Mattelin sites a pin on the elevated right bank was used as the benchmark. At
the Vournas and Pipal sites the right bank is a flood plain, and the pins were
submerged as the stage increased as the ice cover formed. From the available
survey pins and triangulation, the submerged survey pins were re-established. To
avoid the question of whether or not the pin was disturbed by the water and
subsequent ice, the left-bank pin was used as the benchmark. After the survey
alignment was defined, measurement stations were established at 100-ft incre-
ments across the river. Additional stations at 50-ft increments were used in the
vicinity of the thalweg. Supplemental stations were also established at locations
where large gradients in water depth or flow velocity were noticed.
The overall dispositions of banks, ice formation features, and flow peculiari-
ties were noted for all sites. At three sites, video cameras were used to monitor
ice cover formation, breakup, and departure. Fixed-view video cameras were
mounted on poles at the Tveit-Johnson and Pipal sites and under the bridge at the
Culbertson site to facilitate continuous observation of flow, ice, and bank condi-
tions. At the Pipal site, one camera viewed the bank-protected upstream half of
the site, while a second camera viewed a shore protection system and unprotected
area farther downstream. The video cameras proved very useful for gaining an
overall record of ice formation conditions. For instance, the images taken by the
camera at the Tveit-Johnson site were assembled into animations showing a
dramatic sequence of bank failure. Images from the video-camera views were
accessible near-real time via an Internet web site (http://www.crrel.usace.army.
mil/ierd/scour).
At the Culbertson pump site, seven scour probes were placed in the riverbed
upstream of the Highway 16 bridge, located at the downstream end of the site.
The probes provided continuous records of vertical changes in bed level through-
out the winter. The bed elevation data were augmented with water pressure,
water temperature, and air temperature measurements. Microwave and ground-
penetrating radar were tested for use during the first winter survey. However, the
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