APPENDIX B
Analysis of Selected Sediment Transport Relationships
B.1 BACKGROUND
This appendix provides a review of several bed material load equations and provides the
background for several modifications to selected equations. The equations are tested,
developed, and verified using a large group of field and laboratory data for a wide range of
river and bed material sizes.
Sediment transport in rivers has been studied and applied for centuries. Research continues
because the analysis of bed material transport involves complex interactions among many
interrelated variables (Vanoni 1977; Ackers and White 1973 and 1980; Simons and Sentrk
1992). Several sediment transport relationships for alluvial rivers have been proposed during
the last 50 years. These are based upon simplified and idealized assumptions and limited
field data. Due to the complexity of the problem, most existing equations are empirical and
semi-empirical and/or heavily based upon laboratory data and assumptions that are not
totally justified (Cao et al. 1997; Paceco-Ceballos 1989; Tywoniuk 1972). These methods
have been developed based upon theoretical considerations and/or statistical interpretations
of data, and some have been based upon the physics of particle motion. Other methods
have been developed from experimental work, some were derived empirically, and some
represent a combination of theories, experiments and empirical methods, but no
comprehensive study has ever been presented for the total range of alluvial rivers for which
data exist.
In practice, engineers have dealt with a variety of granular materials in applying the
governing laws of transport and movement of sediments (Bogardi 1974). However, 3-
dimensional, time-dependent phenomena still need to be studied, and available knowledge
to conduct these analyses is still insufficient (Overbeek 1979; and Borah et al. 1982a and
1982b). In addition, field verification data have not been utilized to validate the various
relationships to a significant degree (Simons and Sentrk 1992).
Rivers transporting large sediment loads are found throughout the world. Most sediment
transport equations can predict with acceptable accuracy sediment transport in small rivers
since the measurement of pertinent data to develop empirical relations is relatively easy.
However, due to the difficulty of gathering information and required data for large rivers,
extrapolation of methods to estimate sediment loads usually do not give accurate results
(Posada 1995). Hence, the subject of total bed-material transport in large rivers is a
challenge and needs further investigation.
Most investigators have recognized these facts. However, the sediment problem remains
complex and warrants further investigation (Williams and Julien 1989). To date, accepted
methodologies are not able to accurately calculate sediment transport in order to give
acceptable results encompassing all alluvial channel conditions. In other words, there is no
single equation which can calculate sediment transport for the entire range of conditions
found in the field (Alonso et al. 1982; Shen and Hung 1983; Steven and Yang 1989; Simons
and Sentrk 1992; Julien 1995). As a result, calculations of sediment transport using
existing methods for specific rivers with the same input data produce a wide range of
estimates of sediment transport. Because of the complexity of the problem, identification of
B.1
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