122
B. J. Haupt· K. Stattegger . D. Seidov
z'0
o
Qj
>
Grain size [~ml
10
100
1E+3
1E+4
1E+5
2 4 6 8
2 4 6 8
2 4 6 8
2 4 6 8
1E-3
Fig.5 Critical velocities for beginning bed load transport and suspension load transport
The well-known Hjulstrom (1935) curve is given as reference
The bed load transport and the suspended load transport are calculated using
their dependence on the reduced bottom velocity Vbot in the l-cm-thick bottom
layer, also called Prandtl's boundary layer (Sundermann and Klocker 1983;
Zanke 1978). The formula for calculating the bed load transport is
[ 2 2 ]2
, ±
=~1O-7 Y s -Yc,b D*2 v where D* =(p g) d
P
w;
v 2
and p""O.7,
(17)
and for calculating the suspension transport is
(18)
The total sediment transport is computed by summing Eqs. (17) and (18):
(19)
The relationship of critical velocities and sediment transport is summarized
in Fig. 4.
A diagram of critical velocities versus grain size is displayed in Fig. 5.