Sediment Transport Concepts - Sediment Transport in Irrigation Canals: A New Approach - page 136

5.3.7 Correction factor for the prediction of the total sediment transport

The cross-section integrated approach is based on the assumption of a
quasi-two-dimensional model and the cross section is composed by a series
of parallel stream tubes (see Figure 5.26). The mean velocity over the
whole cross section will be replaced by the local, non-uniform velocity
( u i ). Within each stream tube, the lateral velocity distribution is considered
to be uniform and therefore can be described in a one-dimensional way.
The sediment transport in each stream tube is considered as a function of
the flow in that stream tube only without taking into account any diffusion
in the y -direction. The sediment transport per unit width given by q s =
MV N

Mu i . The difference
between the total transport values from the mean velocity and the local
velocities requires a correction factor α in order to equal both values for
the total sediment transport. The division of the entire cross section into
small columns of finite width d y (Figure 5.26) results in the sediment
transport through that stream column and the velocity u that is averaged
over the local depth.

will be replaced by each local velocity q s =

Mu N q s = (5.103)

T

dy

m

h 1

h

1

B

Figure 5.26. Schematized
stream column and velocity
distribution in a non-wide canal
(Paudel, 2010).

u

V

Summation of the sediment transport of all the stream tubes will give the
total sediment transport of the cross section.

Mu N d y Q s = (5.104)

T

Using the average of the variables over the whole cross section will also
result in the total sediment transport through the whole section:

B s MV N

Q s = (5.105)