Integrated River Management - River Dynamics and Integrated River Management - page 746

developed for a long period of time in the Awangxiaohe Ravine, and therefore, the stream channel was
stable and riparian vegetation developed well. The development degree of the step-pool system in the
Awangxiaohe Ravine was measured at S p = 0.18. Most of the flow energy was consumed by the step-pool
system and the flow had no energy to carry bed load. Therefore, the rate of bed load transport was
extremely low ( g b = 0.00015 kg/ms). On the contrary, there was no step-pool system in the Dabaini Ravine,
and the measured value of S p was very small ( S p = 0.025). The flow energy was consumed mainly through
bed load motion and the measured rate of bed load transport was g b = 9.3 kg/ms, which was about 60,000
times higher than the value in the Awangxiaohe Ravine.
Because the energy slope resulting form skin friction of sediment grains on the bed is negligible, for
a given stream power a strong bed structure, or high value of S P , is associated with low bed load
transportation; and intensive bed load motion is associated with a low value of S P . Figure 11.32 shows
the measured rate of bed load transport as a function of S P for different values of stream power. For a
given stream power the rate of bed load transport reduced sharply with increasing S P value. If the S P
value was smaller than 0.05, the bed load transportation was very intensive; and if the S P value is larger
than 0.35, the rate of bed load transport reduced to nearly zero.

Fig. 11.32 Measured rate of bed load transport, g b , in 15 rivers in the Xiaojiang River basin as a function of S P for
different values of stream power P

Equation (11.16) can be rewritten as

J qJ J qJ

b S

1 (11.17)

p p

The energy slope resulting from bed load motion J b is proportional to the rate of bed load transport, g b ,
and the energy slope resulting from bed structures, J S , is proportional to the development degree of the
step-pool system, S P . Although the relation between J b and g b and the relation between J S and S P are unknown,
the ratio of bed load rate over stream power, g b / p , may be expressed as a function of S P . Figure 11.33