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Chapter 6 - Analysis of the test results
d) Volume of the scour and deposition on the point bars
Some interesting observations can be made concerning the volumes of the scour holes and depositions
1 (Figure 6.7):
• The eroded volume shows the tendency to increase with higher discharges (Fig. 6.7, bottom).
The influence of the channel slope is not very important (almost constant).
• On one hand the scour volume is significantly influenced by the presence of macro-roughness,
which can be seen at the wide scatter in vertical direction (Fig. 6.7, bottom).
• On the other hand, the volume of the depositions shows less influence due to the presence of
macro-roughness at the outer bank. Especially the second point bar has a quasi constant
deposited volume. The first point bar shows a slight increase of deposited volume for higher
discharges.
Volume of the scour hole / point bar [dm 3 ]
300
200
100
0
-100
-200
-300
-400
Deposition
Volume of the scour hole / point bar [dm 3 ]
300
200
100
0
-100
-200
-300
Erosion - 1st hole
Erosion - 2nd hole
Deposition - 1st hole
Deposition - 2nd hole
Deposition
Erosion - 1st hole
Erosion - 2nd hole
Deposition - 1st hole
Deposition - 2nd hole
-400
-500 Erosion
0.0% 0.1% 0.2% 0.3% 0.4% 0.5% 0.6% 0.7% 0.8% 0.9%
Energy slope S 0 [%]
-500 Erosion
0.00 0.05 0.10 0.15 0.20 0.25
Discharge Q [m 3 /s]
Figure 6.7: Volume of the scour holes and depositions on the point bars as a function of the discharge (bottom)
and the overall energy slope S e,all (top) (including the tests with macro-roughness, without Peters tests)
1. The volumes were measured above / below a regular bed level corresponding a plane with a
constant slope over the whole channel fitting the bed surface at the beginning and the end of the
channels.
page 122 / November 9, 2002
Wall roughness effects on flow and scouring