7087

• UCREFRP Catalog Number: 7087
• Author: Elliot, J. G., J. E. Kircher and P. V. Guerard.
• Title: Sediment Transport in the Lower Yampa River, Northwestern Colorado.
• USFW Year: 1984.
• USFW - Doc Type: Denver, CO.
• Copyright Material: NO

Table 2.--Particle size statistics for sediment in the
Deerlodge Park study reach
Silt- and clay- si-ze content
Median grain size (percent, by weight, finer
(dso in millimeters) than 0.062 millimeter)
Type of Sample Standard
sediment size Mean deviation
Standard
Mean deviation
Bed material---- 34 0.61 0.17 O.I 0.1
Bedload--------- 32 .57 .12 .1 .1
Suspended
sediment------ 34 ---- ---- 60.0 23.7
in the sand-size range. Virtually all silt- and clay-size material in the
Yampa River at Deerlodge Park was transported in suspension. Silt- and clay-
size material in bed-material samples averaged less than 1 percent by weight
(table 2).
The Yampa River at Deerlodge Park had a mobile bed for the duration of
this study; movement of bed material- was observed over the entire range of
discharges measured in 1982 and 1983. Material comprising the channel bed at
Deerlodge Park was in the sand-size range and relatively uniform in size.
Bedforms could not be observed due to turbidity and the depth of water. No
coarse grain lag deposits were detected at the section where discharge and
sediment measurements were made, and it appeared that all sizes of bed-
material particles in the channel could be transported by the prevailing flow
regime. The Shield's dimensionless shear stress relation (Shields, 1936) may
be used to estimate the particle size of bed material at the threshold of
movement for a given shear stress; therefore, the competence (maximum particle
size transportable) of the Yampa River at Deerlodge Park may be estimated for
various discharges. By definition:
do =
where:
c of movement,
D =mean channel depth in ft,
S =channel slope,
DS
(Ys/Y - 1) tic
(304.8 mm/ft}
d =particle size of bed material in mm at threshold
Ys/Y = ratio of specific weights of sediment and water = 2.65, and
z*c =dimensionless critical shear stress.
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