Flow Depth
0.46
0.46
Q
500
= y o1 b2
=8
= 2.2 ft
y o2
Sand bed:
Q
8000
b1
0.40
0.4
Q
1
= y o1 b2
=8
= 2.6 ft
y o2
Gravel bed:
Q
16
b1
Channel width
0.46
0.46
Q
1
W2 = W1 b2
= 250
= 70 ft
Sand bed:
Q
16
b1
-0.33
0.53
-0.33
0.53
D s2
Q
1
8
W2 = W1 b2
= 250
= 25 ft
Gravel bed:
Q
Ds
16
0.6
b1
1
Friction slope
-0.46
-0.46
Q
1
-4
= 9 x 10 -4
= S f1 b2
= 2.5 x 10
S f2
Sand bed:
Q
16
b1
1
-0.4
-0.4
D s2
Q
-4 1
8
= 2.5 x 10
= S f1 b2
= 0.01
S f2
Gravel bed:
Q
Ds
16
0.6
b1
1
Velocity
0.08
0.08
Q
1
V2 = V1 b2
=5
= 4 ft / s
Sand bed:
Q
16
b1
.33
0.07
0.07
.33
D s2
Q
1
8
V2 = V1 b2
=5
= 9.7 ft / s
Gravel bed:
Q
Ds
16
0.6
b1
1
The gravel bed relationships give a steeper, faster flowing and narrower channel as compared
to the sand bed relationships. Unless the sediment size is markedly different for two streams,
the resulting hydraulic geometry calculated from both sets of equations will be similar.
5.9.7 PROBLEM 7 Downstream Sediment Size Distribution
Measurements of sediment size in the St.-Lawrence Seaway between Cornwall and Valleyfield
are given in the following table.
5.74
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