Sediment Movement in Alluvial Rivers - River Dynamics and Integrated River Management - page 288

Diameter of sediment : 0.40 - 30 mm
These data have quite a large scope, especially notable are those for gravel with a size of 30 mm.
Therefore, the formula is more reliable than some of the others for rivers carrying coarse sand and gravel.
The Meyer-Peter and Muller formula has been widely used in Europe, and the results obtained from it
are generally satisfactory.
A point to note is that the flow velocities in the experiments were relatively high so that almost all of
the sediment could be carried by the flows. For mountain rivers in China, however, many of the particles
on the bed cannot be moved except in extreme events. The Meyer-Peter and Muller Formula predicts a
larger bed load transport rate than is the observed in such cases (Du et al., 1980).
The Meyer-Peter and Muller formula was obtained from experiments with relatively uniform sediment.
In natural streams with various sizes of bed material the flow selects different materials as bed load to
meet its sediment demand for different flow discharges and the relation between the rate of bed load
transportation and flow intensity is very different from the formula.

5.2.2.3 Suspended Load Transportation
Since suspended particles move with the same velocity as the local flow, u , the average transport rate of
suspended load per width, q s , can be solved as follows:

³ h q S u y d (5.48)

s v

a

in which “ a ” is the distance from the lower boundary of the suspension region to the bed, and S v the
volumetric concentration of suspended load at a distance y above the bed. The concentration distribution
of suspended load in open channel flow is given by:

z

S § ·

hya

v

¨ (5.49)

¸

S y h a

© ¹ va

in which

Z
N

z (5.50)

U

*

is a dimensionless number and is called the Rouse Number . With the Eqs. (5.48) and (5.49) one can
calculate the transport rate of suspended load.
Nevertheless, an important problem is to determine the mean sediment concentration, S vm , from known
hydraulic parameters. Velikanov proposed the following formula (Chien et al., 1998),
3

U SK gh (5.51)

vm

Z

in which K is a constant that must be determined and U is the average velocity. Equation (5.51) is the
formula for the depth-averaged concentration of suspended load.
Researchers at the WIHEE (Wuhan Institute of Hydraulic and Electric Engineering) made an extensive
analysis of field data collected from rivers and canals including the Yangtze River, Yellow River, Yongding
River, People's Victory Canal, and Qingtongxia Irrigation System; and they concluded that Eq. (5.51) should
be modified to the following (WIHEE, 1961)

m

§

3

·

U

Sk ¨ (5.52)

¸

vm

gh Z

© ¹

3 UgR Z) as shown in Fig. 5.26.

in which the coefficients k and m are functions of (