Environmental Engineering Reference
In-Depth Information
Q
s
Q
s
L
A
L
A
Q
sa
Q
sa
Q
se
Q
se
deposition
deposition
deposition
erosion
X
X
Backwater case I
Drawndown case I
Q
s
Q
s
Q
se
Q
se
Q
sa
Q
s
erosion
deposition
erosion
erosion
X
X
Backwater case IIa
Drawndown case IIa
Q
s
Q
s
Q
se
Q
se
Q
sa
Q
s
erosion not possible
erosion not possible
X
X
Backwater case IIb
Drawndown case IIb
Q
s
sediment transport rate
Q
sa
actual sediment transport rate
Q
se
equilibrium sediment transport capacity
L
A
adaption lenght
Figure 5.36. Sediment transport
for gradually varied flow.
X
distance
condition. To maintain the water level at the set points for flows smaller
than the design values, the gates are lowered, which will create a backwater
effect resulting in non-equilibrium sediment transport conditions.
Therefore the design approach should be modified in such a way that
the actual sediment movement scenario is reflected. Only then will the
designed canal result in an improved sediment transport under changing
flow conditions.
5.5 CONCLUSIONS
Applications of the existing sediment transport concepts under flow con-
ditions and sediment characteristics prevailing in irrigation canals were
used to evaluate the suitability of those concepts. In this way any increase
in the unavoidable uncertainties and inaccuracies during the computations
of the sediment transport can be kept to a minimum. From the analysis of
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