Flow Diagrams - Sediment Transport in Irrigation Canals: A New Approach - page 287

APPENDIX F

Flow Diagrams

Start
Compute T, D*

N

T > 0

Y

Bed form is ripple
equivalent roughness
Ksb = 200d 50

D* < 10
and T < 3

Y

Erosion or
deposition

N

N

Delta = Ksb

Ksb = roughness
in the sides

Y

Bed form is dune and
calculate dune height
using van Rijn method

Erosion
or deposition
Deltaz <> 0

Ksb = min.
roughness

Y

Erosion
or deposition
Deltaz <> 0

Y

Y

Ksb = min.
roughness

N

Delta < Deltaz

N

N

Delta < Deltaz

Delta = Deltaz

Y

Delta = Delta

Y

Delta = Deltaz Delta = Delta

Calculate Ksb using
van Rijn method

Ksb = Delta

Ksb < Ksmin

N Y

Ksb < Ksmin

N

Y

Ksb = Ksb Ksb = Ksmin Ksb = Ksb Ksb = Ksmin

Note:
1

Legend:
Ksb = Equivalent roughness height at bed
Deltaz = deposition depth
Delta = bed form height
Min = minimum
Ksmin = minimum roughness height corresponding

If there is no initiation then roughness
height at the bed is equal to the minimum
height as entered from input
If there is initiation of motion then
roughness height is calculated depending
upon the type of bed form
The roughness height calculated is not less
than the height of deposition or erosion in
one time step

2

to bed material

T = mobility parameter

3

D* = grain shear parameter

d 50 = mean sediment size

Figure F.1. Roughness prediction procedure depending upon the flow condition and sediment parameter (Paudel, 2010).