Environmental Engineering Reference
In-Depth Information
in which the median size of the sediment is smaller than 0.15 mm and
the geometric standard deviation is greater than 2.
A.5 VAN RIJN METHOD
The van Rijn method (1984a and 1984b) computes the total sediment
transport. The total transport is the summation of the bed and suspended
load transport (
q
s
=
q
sus
). The bed load transport
q
b
is given by the
product of the saltation height, the particle velocity and bed load concen-
tration. The method assumes that the gravity forces dominate the motion
of the bed particles. The method of van Rijn has been evaluated with data
from tests that had the following characteristics:
- mean velocity
q
b
+
=
0.31-1.29 m/s
- flow depth
0.1-1.0 m
- median diameter
=
=
0.32-1.5 mm
The bed load transport
follows from:
q
b
=
u
b
δ
b
c
b
(A.19)
- Particle velocity
u
b
u
b
=
1
.
5
T
0
.
6
[(
s
1)
gd
50
]
0
.
5
−
(A.20)
- Saltation height
δ
b
:
δ
b
=
0
.
3
D
0
.
7
∗
T
0
.
5
d
50
(A.21)
- Bed load concentration
c
b
:
0
.
18
c
o
T
D
∗
c
b
=
(A.22)
with:
(
u
∗
)
2
(
u
∗
,cr
)
2
(
u
∗
,cr
)
2
−
=
T
(A.23)
g
0
.
5
V
C
u
∗
=
(A.24)
(
s
1
/
3
−
1)
g
ν
2
D
∗
=
d
50
(A.25)
Replacing equations A.20 to A.25 in equation A.19 gives:
1)
0
.
5
g
0
.
5
d
1
.
5
50
D
−
0
.
3
T
2
.
1
q
b
=
0
.
053(
s
−
(A.26)
∗
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