Hydraulic Design of Irrigation Canals - Sediment Transport in Irrigation Canals: A New Approach - page 259

follows the criterion for the continued conveyance of suspended mate-
rial, namely y

∗

S 1 / 3 should be constant or non-decreasing in downstream

direction.

C.8 TRANSPORT OF THE BED MATERIAL

In general the bed load particles in canals have a diameter of D >
50 10 − 3 (mm) and their transport on or above the bottom

is determined by the shear velocity ( v ∗ ) with v ∗ =

10 − 3 -70 ∗ ∗

S ) 0 . 5 .
The criterion for continued conveyance of the bed load depends on
the water and sediment transport formulas, for example Einstein-Brown,
Engelund Hansen, Ackers-White, Brownlie, etc.
The relative transport capacity is:

( g ∗ y ∗

y 3 S 3 T

Q ∝

b ∗ ∗

(C.29)

b ∗ y ∗ y x ∗ S z

Where x and z are exponents depending on the choice of the water
transport relationship.
The criterion for the continued movement of suspended load for a wide
canal gives that yS 1 / 3 should be constant or non-decreasing. To prevent
erosion the boundary shear stress should be constant. From this follows
that y

∗

S should be constant (or non-decreasing). Therefore it would be
expected that for sediment laden water that only transports bed load, the
criterion for continued conveyance of the sediments should be some where
in between these two criteria. The criterion to convey non-suspended
(bed) material depends strongly on the water and sediment equations. The
best criterion is that the relative transport capacity for bed load should
be non-decreasing or in the case of possible erosion, should remain
constant. The numeric approximation for this transport is that y 1 / 2

∗ S

is constant or non-decreasing.
To prevent erosion the boundary shear stress should be constant,
which gives that y

S should be constant (or non-decreasing). Therefore
it would be expected that for sediment laden water that transports only
bed load, the criterion for continued conveyance of the sediments is
some where in between these two values. The criterion to convey any
non-suspended material depends strongly on the water and sediment
equations; the best criterion would be that the relative transport capac-
ity for bed load should be non-decreasing, or in the case of possible
erosion, should remain constant. The best numeric approximation for
the conveyance of non-suspended material is that y 1 / 2

∗

∗ S is constant or

non-decreasing.