Yampa River Overview

• Description: Yampa River Management Plan
• State: CO
• State: UT
• State: WY
• Basin: Yampa/White/Green
• Water Division: 6
• Date: 1/1/3000
• Title: Yampa River Overview
• Water Supply Pro - Doc Type: Report/Study

Table 5. Inflection Points of the Means for Riffles (Method B) for Strata 6, Strata 8
and combined.
Variable
Units
Strata 6
Strata 8
Combined
Wetted Perimeter
(cfs)
80
200
150
( %)
43%
57%
53%
Wetted Width
(cfs)
100
200
150
(ft)
143
199
178
Average Depth
(cfs)
100
125
125
(ft)
0.58
0.61
0.61
Change in Stage
(cfs)
80
150
80
(ft)
0.33
1.15
0.89
Width /Depth Ratio
(cfs)
125
150
200
(ratio)
290
319
307
Average Velocity
(cfs)
125
100
125
(ft/s)
1.55
1.31
1.45
Figures 2s in Appendix 5A and 6A present the variability of stream width with
flow, expressed by the coefficient of variation. In Strata 6 variation in stream width
declines as flow increases. This indicates a wide variability in stream width at lower
flows, but at higher flows width on riffles become more uniform. The C.V. inflection
point for Strata 6 is 200 cfs at 28% percent C.V. In Strata 8 the inflection point the C.V.
curve was 125 cfs, and this was its maximum value of 30 %. In Strata 8, the C.V. value
did not fall below 30 %, for flows between 150 to 500 cfs. Variation in stream width
(C.V.) was higher in Strata 8 than Strata 6 at all flows over 150 cfs, and the slope of the
line was flat. This indicates a constant (Strata 8) instead of decreasing (Strata 6)
variance. This difference is explained by the fact that many cross sections in Strata 8
were in Little Yampa Canyon. This river reach appeared to be much less influenced by
anthropomorphic activities (grazing, roads, homes) that tend to reduce channel stability
and which may lead to increased channel width.
The approach that used the mean of individual inflection points (Method A) produced
higher values than the technique that more simply used the inflection point for the mean
20