B.2.3 Analysis of Sediment Transport Relations
The field data were divided into two categories: Group 1 for analysis of the selected
sediment transport relations and proposed equations, and Group 2 for verification and
validation of the proposed methods. The river data sets were divided into two parts in
random order.
A comparison between computed results and field data was conducted and examined.
Statistical approaches were used including the mean discrepancy ratio RD (Bechteler and
Vetter 1989; Wu 1999; Nakato 1990; Yang and Wan 1991; and Hydrau-Tech, Inc. 1998), and
the correlation coefficient CC (Hydrau-Tech, Inc. 1998). The equations for each parameter
follow:
Ri
X
RD =
, Ri = i
(B.1)
N
Yi
(Xi - X)(Yi - Y )
Cc =
(B.2)
(Xi - X) (Yi - Y )
2
2
For perfect fit, the values in Equations B.1 and B.2 are RD = 1 and Cc = 1.
The sediment relations were used to calculate the transport of sediment using data from
Group 1. The sediment load was calculated using mean diameter of riverbed material
(uniform sediment size). The results of comparing computed sediment concentration (Cppm)
and measured sediment concentration measured for four ranges of particle sizes and for
three sizes of rivers are shown in Figure B.1a through d, and Figure B.2a through c.
B.2.4 Summary of Applicability of Ten Sediment Relations Analyzed
The applicability of these relationships as reported by Kodoatie et al. (1999) is illustrated in
Table B.4. While certain equations appear to be more applicable to particular bed
characteristics or river size, each equation could, potentially, be applied with reasonable
results for a specific river, if the river characteristics are compatible with those used in the
equation's development. For any specific river, it is recommended that the results be
compared with actual measurements. The following conclusions can be drawn from the
results of this analysis:
1. Gravel-bed rivers (2 mm < D50 < 64 mm)
Compared to the measured values, none of the selected sediment relations can accurately
predict the sediment discharge. The closest values based upon the discrepancy ratio are
Ackers and White with RD = 0.33 and Brownlie with RD = 4.25. However, based upon the
Pearson correlation coefficient for comparison of computed to measured Cppm, the best
equations are Bagnold and Shen and Hung, both with Cc of 0.70. Considering gravel-bed
rivers, Brownlie's equations, although developed for sand-bed rivers, are the most
acceptable of the ten equations.
B.6
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