1400 ‎(2)‎

• UCREFRP Catalog Number: 1400
• Author: Simons, D. B., et al., ed.
• Title: Proceedings
• USFW Year: 1980.
• USFW - Doc Type: Workshop on Downstream River Channel Changes Resulting From Diversions or Reservoir Construction.
• Copyright Material: NO

"~:"

Hydraulic and Sediment Characteristics at Maybell

The data regardi ng the mean monthly di scharges and the maximum
annua 1 di scharges of the Yampa River at Maybe 11 have been call ected
since 1910. However, the gage heights are known only for the maximum
annual discharges and even in this situation it is not known how these
gage heights are related with the depths of flow. The sediment data
include the size distribution of bed and suspended material along with
the mean monthly concentration of the suspended load from 1951 to 1957
and 1977 to 1978. These data have been used to study the hydraulic.and
sediment characteristics of the Yampa River at Maybell.

Stage-Discharge Relationship. Figure 3 shows the stage-discharge
relationship at Maybell. A close examination of this figure indicates
that the gage heights corresponding to the same discharge are different
for different years. Such a variation in the gage height would imply
tha t the stream is not in true equil i bri um and is ei ther aggradi ng or
degrading. To examine this aspect more thoroughly, the gage heights
were plotted against time for different ranges of discharge as shown in
Figure 4. It is interesting to note that gage heights increased
continuously up to 1950 and have stabilized at constant values since
then. This may be taken to be an indication of aggradation until 1950
and subsequent attainment of equilibrium conditions at its present
slope.

Relation between Stage and Depth of Flow. In the absence of any
definite relationship between the stage and the depth of flow, it was
nece~sary to estimate the depth of flow for the given discharge and the
slope. The size distribution of the bed material of the Yampa River is
shown in Figure 5 which shows that the size of the bed material ranges
from 4.0 mm to 128.0 mm with a median size of 40.0 mm. Considering the
coarseness of the bed materi a 1, the bed was assumed to be fl at and the
value of Manning's roughness coefficient n, was computed using
Equations 5 and 6 proposed by Bray (1979) and Strickler (see Garde and
Ranga Raju, 1977) respectively

n = .104 SO.177

(5)

n =

(d ) 1/6
65
21.0

(6)

Here 5 is the bed slope and d65 is the size of the bed mater1 a 1 in
meters such that sixty-five percent of the material is finer than this
size.

The values of n obtained from Equations 5 and 6 were 0.0285 and
0.029 respectively and thus a constant value of n = 0.03 was adopted in
the subsequent calculations.

33

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