7930

• UCREFRP Catalog Number: 7930
• Author: Ketcheson, G. L.
• Title: Sediment Rating Equations
• USFW Year: 1986.
• USFW - Doc Type: An Evaluation for Streams in the Idaho Batholith.
• Copyright Material: NO

Table 2-Comparative sediment yields for Silver Creek streams, Idaho

tream

ear Total sediment yield estimates in megagrams per year
Hand samples Sediment Pumped samples
Rating Time dam Rating Time
equations integration yield equations integration
SC-1 78 13.8 17.1 16.8
79 5.4 7.3 5.3 1.9 2.1
80 31.2 45.3 44.6
81 16.2 10.7 15.4 5.3 3.4
82 46.9 57.2 61.1
SC-2 78 16.7 9.3 7.2
79 1.5 1.5 3.4 .7 .6
80 22.0 38.0 42.8 5.6 1.2
81 10.3 5.3 9.3 2.1 2.5
82 59.0 54.3 60.1
SC-3 75 20.1 19.8 14.4
76 16.7 20.9 11.4
78 - 8.9 11.9
79 - 1.6 2.9 2.2 .6
80 14.9 24.8 14.1 1.5 4.1
81 11.1 4.4 7.3 1.6 2.6
82 56.2 31.8 41.8
SC-4 75 22.7 21.3 19.3
76 - 22.0 27.8
78 - 11.2 50.4
79 - 2.6 4.5 1.0 .7
80 15.6 18.0 50.6 8.7 14.4
81 12.5 12.0 43.5 7.0 16.6
82 91.1 128.6 135.9
SC-5 75 - 32.3 12.1
76 - 18.9 17.4
78 - 15.0 13.6
79 - 1.3 2.7 1.6 1.9
80 11.8 14.3 10.6 11.9 13.7
81 15.2 8.8 8.5 2.9 4.8
82 36.8 24.9 44.4
SC-6 75 19.4 28.7 25.6
76 21.1 32.6 26.9
78 21.0 29.5 21.0
79 1.5 1.9 3.5 1.5 1.2
80 25.3 39.8 20.8 10.3 12.0
81 9.5 7.4 9.1 4.3 3.1
82 61.2 67.9 68.9
The large variance associated with sediment data may
have masked differences in estimates from various tech-
niques, but the differences did exist. Only 26 percent of
the time-integration estimates and 21 percent using rat-
ing equations were within 10 percent of the sediment
dam estimates. Table 3 shows that nearly 50 percent of
the estimates were within the 25 percent error band, but
also that some estimates were 100 percent or more
different.
Several factors were used to try to explain why some
sediment yield estimates from rating equations were
within 10 percent of "actual" while others were more
than 50 percent different. These included the number of
samples on the rising versus the falling limbs of the
hydrograph, statistical significance of the suspended
sediment and bedload equations, and the sample year.
Table 3-Percentages of sediment yield estimates within
specified error bands around the sediment dam
estimates
Percent of estimates within given error
From From
Percent rating time
error equations integration
10 21 26
25 55 45
50 76 74
80 97 92
100 97 97
150 100 97
200 100
9